With the novel coronavirus outbreak globally, many people are understandably concerned about their health and safety.

In this post we’ll look at the difference between respirator filtering standards such as N95 and FFP2/FFP3…

Masks vs Respirators

Before we go any further, let’s just clarify on a technical difference between a “mask” and a “respirator”. In day to day language we often say mask, when referring to what are technically called respirators.

Uses for Masks:

  • Masks are loose fitting, covering the nose and mouth
  • Designed for one way protection, to capture bodily fluid leaving the wearer
  • Example – worn during surgery to prevent coughing, sneezing, etc on the vulnerable patient
  • Contrary to belief, masks are NOT designed to protect the wearer
  • The vast majority of masks do not have a safety rating assigned to them (e.g. NIOSH or EN)

Uses for Respirators:

  • Respirators are tight fitting masks, designed to create a facial seal
  • Non-valved respirators provide good two way protection, by filtering both inflow and outflow of air
  • These are designed protect the wearer (when worn properly), up to the safety rating of the mask
  • Available as disposable, half face or full face

Respirator Standards

Whilst surgical style masks are not redundant by any means (discussed more below), they aren’t designed to protect the wearer, whilst respirators are.

The US Center for Disease Control (CDC) cites the N95 respirator standard as part of the advised protective equipment in their Covid-19 FAQ and their SARS guidance (SARS being a similar type of Corona virus). Which suggests that an N95 or better respirator is acceptable.

N95 vs FFP3 & FFP2

The most commonly discussed respirator type is N95. This is an American standard managed by NIOSH – part of the Center for Disease Control (CDC).

Europe uses two different standards. The “filtering face piece” score (FFP) comes from EN standard 149:2001. Then EN 143 standard covers P1/P2/P3 ratings. Both standards are maintained by CEN (European Committee for Standardization).

Let’s see how all the different standards compare:

Respirator StandardFilter Capacity (removes x% of of all particles that are 0.3 microns in diameter or larger)
FFP1 & P1At least 80%
FFP2 & P2At least 94%
N95At least 95%
N99 & FFP3At least 99%
P3At least 99.95%
N100At least 99.97%

As you can see, the closest European equivalent to N95 are FFP2 / P2 rated respirators, which are rated at 94%, compared to the 95% of N95.

Similarly, the closest to N100 are P3 rated respirators – with FFP3 following closely behind.

You could approximate things to say:

KN95 vs N95

According to 3M (source), the Chinese KN95 standard has an equivalent specification to N95/FFP2 respirators . To quote:

“It is reasonable to consider China KN95, AS/NZ P2, Korea 1st Class, and Japan DS FFRs as equivalent to US NIOSH N95 and European FFP2 respirators”

In practice the issue is more complex, and I wouldn’t take for granted that all KN95 respirators are up to the same standard.

Things to watch out for:

  • Typically KN95 respirators are held in place by over-ear elastic loops, rather than behind the head elastics. This can result in a weaker seal. Fortunately there are methods for tightening – see this YouTube video for ideas. Products called “ear savers” can also aid with tightening, and can be found on eBay or you can 3D print them.
  • There’s no guarantee that all KN95 respirators actually meet the Chinese KN95 standard. However, with the current respirator shortage, unfortunately the same goes for N95/FFP also.

The KN95 specification is referred to as GB 2626-2006 (preview here) – so you will generally see that written on the KN95 respirators. From July 1st 2020, it’ll be replaced by GB 2626-2019, an updated specification (preview here).

I’ve linked below to a supplier of KN95 respirators in the USA – in case it’s of use to some readers.

Are N95/N100 actually better than FFP2/P3?

Not necessarily, it’s important to note that these standards only specify the minimum % of particles that the respirator filters. For example, if a mask is FFP2 rated, it will filter at least 94% of particles that are 0.3 microns in diameter or larger. But in practice it will filter somewhere between 94% and 99%. The precise figure will often be quoted by the manufacturer in the product description.

A good example is the GVS Elipse respirator, which in the USA (link) is rated at P100 (99.7%), and in Europe (link) is rated at P3 (99.95%). In practice it’s likely to have the same filtering capacity in both regions.

Valve vs Non-Valved Respirators

✅Valved respirators make it easier to exhale air. This makes them more comfortable to wear, and leads to less moisture build-up inside the respirator. Ideal for things like DIY/construction work.

❌The problem with valved respirators is that they do not filter the wearer’s exhalation, only the inhale. This one-way protection puts others around the wearer at risk, in a situation like Covid-19. It’s for this reason that hospitals and other medical practices do not use valved respirators.

One hack to protect (and respect) others when wearing a valved respirator is to put a surgical mask or “cloth face covering” over the valved respirator, to (partially) filter the out breath.

How big is the Coronavirus, and can respirators filter it?

TL;DR – yes, respirators with high efficiency at 0.3 micron particle size (N95/FFP2 or better) can in theory filter particles down to the size of the coronavirus (which is around 0.1 microns). What that doesn’t tell us is how much protection respirators will provide against coronavirus when in use – we will need to wait for future studies to confirm.

Read on to learn more…

A recent paper shows that the coronavirus ranges from between 0.06 and 0.14 microns in size. Note that the paper refers to the coronavirus particle as 2019-nCoV, which was it’s old name. The virus is currently called SARS-CoV-2, and the illness it presents in people is called Covid-19.

Respirator’s are measured by their efficiency at filtering particles of 0.3 microns and bigger (noting that the coronavirus is smaller than that).

The reason for the focus on 0.3 microns is because it is the “most penetrating particle size” (MPPS). Particles above this size move in ways we might anticipate, and will get trapped in a filter with gaps smaller than the particle size. Particles smaller than 0.3 microns exhibit what’s called brownian motion – which makes them easier to filter. Brownian motion refers to a phenomenon whereby the particle’s mass is small enough that it no longer travels unimpeded through the air. Instead it interacts with the molecules in the air (nitrogen, oxygen, etc), causing it to pinball between them, moving in an erratic pattern.

According to researchers this point between “normal” motion and brownian motion is the hardest particle size for filters to capture.

What we can take away from this, is that high filter efficiency at 0.3 micron size will generally translate to high filter efficiency below this size also.

For more discussion and details on the subject of respirator filters and brownian motion – see this great post at smartfilters.com.

Now lets look at specific research that measures the filter efficiency at 0.3 microns and below (coronavirus territory)…

  • This article by 3M discusses research showing that all 6 of the N95 respirators they tested can efficiently filter lower than 0.1 micron size with approximately 94% efficiency or higher. The graph below is from that article, and illustrates this:

  • Additionally, smartfilters.com have a great article on this subject, citing research showing that the respirators tested could filter down to 0.007 microns (much smaller than Covid-19). For example the 3M 8812 respirator (FFP1 rated) was able to filter 96.6% of particles 0.007 microns or larger. Suggesting FFP2 or FFP3 would achieve even greater filtration.

The below image (click it to expand) shows the size of the coronavirus, relative to other small molecules like a red blood cell, or the often talked about PM2.5 particle size.

Image of coronavirus vs other particles – from smartairfilters.com

N vs P respirators? (Oil Resistance)

The CDC explains that in the USA there are 3 ratings for protection against oils; N, R or P:

  • N = Not resistant to oil
  • R = somewhat Resistant to oil
  • P = strongly oil Proof

What this means in practice, is for industrial settings, where the air might contain a lot of oil particles, if the mask isn't P rated, then over time the oil may degrade and reduce the filter performance.

For the vast majority of people trying to reduce exposure to Covid-19, it won't be necessary to protect against oils - this is primarily designed for industrial use settings.

 

Surgical vs Non-Surgical Respirators?

Alongside "regular" respirators, there are also what are often referred to as "surgical" or "surgically approved" respirators. These carry the aforementioned ratings such as N95/FFP2, but are also approved for fluid resistance. A qualification governed by ASTM F1862 - which covers the edge case in which an artery is punctured, and high pressure blood is sprayed directly at the respirator. To pass the test, the mask has to withstand this spray without leaking fluid inside the mask.

You can see why this type of mask if important for surgery, but it's not clear outside of that setting how much extra benefit it would provide. Regular N95/FFP2 masks will block things like coughs and sneezes.

The comparison table below shows how a regular N95 mask (8210), stacks up against 2 surgical N95 masks (1860 and 1870+).

Example of Surgical vs Non-Surgical Respirators

See this comparison table below for the key differences (source: 3M website):

  N95 Respirator 3M Model 8210 Surgical N95 Respirator 3M Model 1860 Surgical N95 Respirator 3M Model 1870+
 
Designed to help protect the wearer from exposure to airborne particles (e.g. Dust, mist, fumes, fibers, and bioaerosols, such viruses and bacteria)
Designed to fit tightly to the face and create a seal between the user’s face and the respirator
Meets NIOSH 42 CFR 84 N95 requirements for a minimum 95% filtration efficiency against solid and liquid aerosols that do not contain oil
Cleared for sale by the U.S. FDA as a surgical mask
Fluid Resistant - Meets ASTM Test Method F1862 “Resistance of Medical Face Masks to Penetration by Synthetic Blood” which determines the mask’s resistance to synthetic blood directed at it under varying high pressures[1] ✅ 120 mm Hg ✅ 160 mm Hg

According to the 3M wesbite:

[1] "ASTM F1862 is a standard test method for resistance of medical facemasks to penetration by synthetic blood. This test is required because during certain medical procedures, a blood vessel may occasionally be punctured, resulting in a high-velocity stream of blood impacting a protective medical facemask. The test procedure specifies that a mask or respirator is conditioned in a high-humidity environment to simulate human use and is placed on a test holder. Synthetic blood (2cc) is shot horizontally at the mask at a distance of 30 cm (12 inches).

Surgical masks and respirators are tested on a pass/fail basis at three velocities corresponding to the range of human blood pressure (80, 120, and 160 mmHg). The inside of the mask is then inspected to see if any synthetic blood has penetrated to the inside of the facemask. Fluid resistance according to this test method is when the device passes at any level."

In essence, all 3 of these masks should be adequate, as per CDC guidance on 2019-nCoV and SARS. As mentioned above, where the 1860 and 1870+ are superior to the 8210 is when faced with high velocity liquid spray - which is possible during surgery (e.g. punctured artery), but unlikely in day-to-day usage.

Risks With Using Respirators

There are a number of possible risks with respirators that it’s worth being aware of, so that you can avoid making them.

  1. Not fitting and wearing respirators correctly – A respirator can’t fully protect you if it doesn’t fit your face. See OSHA guidance on fit testing and fit checking for more info.
  2. Touching the front of the respirator (which catches viruses etc) and then transferring that to other objects, which could eventually lead back to your mouth and nose.
  3. Taking unnecessary exposure risks because you’re wearing a respirator. Don’t let it give you false confidence. The safest thing is maintaining social distance.

For further discussion on these 3 points, see the expandable box below:

1. Not fitting and wearing respirators correctly

It's important to make sure that the respirators we use form a tight fit on our face, such that all air is being filtered and not passing in through the sides. Under ideal situations, one would try on a number of respirators to find one that fits perfectly. After that, you would "fit test" the respirator by putting it on tightly, then checking if you can smell or taste a chemical that you hold nearby. If you can, the seal may not be adequate. If you can't, that suggests you passed the fit test. See more about this process on the OSHA website - including details on their list of approved chemicals for fit testing. However, currently we're under pandemic conditions with shortages on both respirators and the chemicals used for fit testing them. Therefore we have to make-do as best we can with what we've got available. However, a focus on correctly fitting respirators is crucial.

2. Touching the front of the respirator

The front of the respirator can be thought of like a net - catching and filtering viruses and bacteria as we breathe. The problem then occurs if we touch the front of the mask and then touch our faces. In essence we need to treat the front of the mask like it's a hazardous material, and always wash hands carefully after touching it. Also avoiding touching the outside, and then the inside of the mask, because the inside has to make tight contact with your face, and is difficult to clean.

3. Taking unnecessary exposure risks

Don't let wearing a respirator give you confidence to take unnecessary risks. The efficacy of respirators is less than 100%, unfortunately. Both due to their filtering capacity limits (<100%) and due to the 2 points discussed above. So for example, don't go to an event with lots of people (especially if it's indoors), and think it's safe because you're wearing a respirator. The safest thing you can do is practice social distancing.

Reliable Brands?

Prior to the pandemic, there was easy access to reliable brands such as 3M, GVS, Moldex etc. Now, however, their supply is either going to frontline workers (as it should be) or it’s very limited.

This means that the general public are left to either make their own face coverings (discussed below), or do their own due diligence when sourcing less well known brands. Hopefully this whole article helps with that due diligence process.

Below I’ve listed a US retailer who currently have stock, and I’ve happily bought from before (see my brief review of them for more info).

  • Health Bodyguard Store – KN95 rated respirators stocked in Ohio and shipped to all of mainland USA. From $4 to $6 per respirator, depending on quantity

Surgical Masks

Surgical masks are generally speaking a 3-ply (three layer) design, with 2 sheets of “non-woven” fabric sandwiching a “melt-blown” layer in the middle. It’s the melt-blown layer that provides the filtering capability. A melt-blown material is also used in respirators, and thus you can imagine it’s more expensive and hard to come by recently, due to demand.

Image of the melt-blown filaments under microscope come from mdpi.com

The melt-blown fabric is made by melting a plastic, then blowing it from either side at high velocity onto a rotating barrel. Done right, this results in a fabric composed of tiny filaments. For a more technical (!) explanation of the process – see here.

Diagram of melt-blown machinery (left) comes from Erdem Ramazan’s book, and the image of melt-blowing in progress (right) comes from 4FFF on wikipedia

Not all melt blown fabric has the same filtering capability, some are better than others. Unfortunately we can’t test the filtering capability of the melt-blown layer without specialized knowledge and equipment. What we can do, however, is at least check that the melt-blown layer is present.

Below I show an example of a surgical mask (left) that came without the melt-blown layer. You can imagine that, given the extra cost and current scarcity of melt-blown fabrics, manufacturers might cut corners with this layer, so it’s worth keeping an eye on.

Choosing surgical masks that have been tested according to a set of standardized test methods (ASTM F2100, EN 14683, or equivalent) will help avoid low quality products. The ASTM standard for surgical masks (particularly levels 2 & 3) are primarily focused around fluid resistance during surgery. These higher levels don’t offer much extra in the way of protection from Covid-19 under non-surgical conditions.

If you see reference to BFE95/BFE99 - BFE = "Bacterial Filtration Efficiency" - and the score = % of particles blocked, with a mean particle size of 3 microns (+/- 0.3microns) - source.

Similarly, PFE = Particle Filtration Efficacy. ASTM F2100 measures the PFE down to 0.1 microns (source).

This table by Nelson Labs gives more examples of surgical mask specifications, including BFE/PFE.

 

Can Surgical Masks Filter the Coronavirus?

Whilst FFP2/FFP3 or N95/N100 are the gold standard as far as face protection goes, what about surgical masks, do they provide any protection?

Strictly speaking, surgical masks are primarily designed to protect vulnerable patients from medical professionals. Stopping the wearer (e.g. surgeon) from spreading their germs when coughing/sneezing/speaking. So they’re designed to protect patients, not to protect the wearer.

An obvious flaw with surgical masks compared to respirators is their lack of a tight face fit, which leaves gaps around the edges.

There isn’t currently research available on the efficacy of surgical masks (or even respirators), for protecting wearers against the coronavirus. Although this isn’t totally surprising given how new the virus is.

In lieu of that, the below looks at research around the use of surgical masks and N95 masks in the context of influenza, looking specifically at the protection given to the wearers. Influenza may be a good virus particle to compare it to, as they are both transmissible through droplets and aerosol, both cause respiratory infection, and both are similar in particle size.

N.B. Please don’t conflate the comparison to the influenza particle as suggestion that they are comparable illnesses – current data suggests that the coronavirus may have a higher mortality rate.

Source for coronavirus (SARS-CoV-2) size is this paper, whilst sources for Influenza size are this paper (eventually published in Vaccine), and a Frontiers in Microbiology paper.

In the first study we will look at, 2,862 US health care personnel were split into 2 groups, those wearing N95 masks and those wearing surgical masks1. There were 207 lab confirmed influenza events in the respirator wearing group, compared to 193 in the mask wearing group – a difference that was not statistically significant.

In the next study, Canadian nurses were split into 2 groups, those wearing N95 masks and those wearing surgical masks. There were 50 cases of influenza in the surgical mask group, compared to 48 in the N95 respirator group2. Again, no significant difference.

So where does this leave us? Those 2 studies suggest that surgical masks are approximately comparable to N95 masks when it comes to preventing influenza illness in close contact clinical settings. What this doesn’t tell us, is whether they’re better than wearing nothing on our faces.

To find that out, we need a study that has a control group that doesn’t use any facial protection. Due to ethical considerations, those studies aren’t abundant, but we do have at least one.

In this Australian study, they looked at 286 adults in 143 households who had children with influenza-like illness3. For clarity, influenza-like illness is not the same as laboratory confirmed influenza. It’s diagnosed by symptoms like fever, dry cough and feeling sick, which could mean influenza, but could also be caused by the common cold or other viruses. They found that adults who wore masks in the home were 4 times less likely than non-wearers to be infected by children in the household with a respiratory infection. There is nice analysis of the study here by Imperial College London.

It’s definitely fair to note that this Australian study was very small, and could not be considered definitive by any means. That being said, we’ve got to work with what he have, and this at least gives us some data points:

  • Wearing a surgical mask or N95 (FFP2) respirator was better (in the study) at protecting against influenza-like illnesses than wearing nothing at all
  • Whilst we can anticipate surgical masks to be inferior to respirators, the studies above suggest they are not as inferior as one might assume. For example the first two studies didn’t find a significant difference between surgical masks and N95 respirators, when protecting wearers against influenza.
  • Important to note that we’ve used influenza protection as a proxy for SARS-CoV-2 (coronavirus). This is done because SARS-CoV-2 is new and there are no comparable studies on it. But of course the drawback is that it still leaves a lot of uncertainty, as SARS-CoV-2 may act quite differently in terms of transmission.

In a lab setting, with artificial conditions, we find that surgical masks are able to block 80% of particles down to 0.007 microns. Compared to the 3M 8812 respirator in this study which blocked 96% (FFP1 rated). This generally aligns with our discussion above.

In conclusion: we don’t know how much protection surgical masks provide against the novel coronavirus. However, the above at least suggests that a surgical mask may provide more than zero protection – and that’s worth being aware of. It makes sense to only wear them for protection as a method of last resort – with respirators being the primary choice.

It is much safer to avoid the company of people who are sick or potentially sick, and to reduce social contact overall, especially to large groups of people (see the social distancing section below). To repeat, the use or surgical masks would have to be a last resort – and wearing one should not encourage anyone to take unnecessary exposure risks.

If we are in the presence of someone sick, who has/might have the coronavirus, it makes sense for them to wear a mask or respirator to reduce their ability to spread the disease.

DIY / Homemade Masks

The CDC has recently announced guidance to American citizens that “cloth face coverings” should be used in public settings where social distancing measures are difficult to maintain. Noting that surgical masks and N95 respirators should be reserved for healthcare workers. If citizens don’t buy respirators or surgical masks, they’re left to buy fabric based masks from places like Amazon (yes, they do have some), or, they need to make their own.

Image from the masks4all.co DIY mask project

So how does one make their own mask?

Firstly, it’s worth noting how various household items compare in terms of filter efficacy and breathability. For that, we can refer to a Cambridge University study (link), which revealed “the pillowcase and the 100% cotton t-shirt were found to be the most suitable household materials for an improvised face mask”.

Image via SmartAirFilters

Interestingly, other items such as vacuum cleaner bags and dish towels showed greater filtration capacity, so why didn’t the study pick them? Unfortunately those items performed badly in the breathability tests. A mask is little good if you can’t breathe out of it. See this write-up of the study for more details (and nice graphs!)

Below are some DIY mask methods, listed from simple to advanced:

1) No modifications T-Shirt Mask
Don’t want to get the scissors out? No problem. This method shows how to wrap a T-shirt around your face without adjusting it. Based on the above study, use 100% cotton t-shirts where possible. Find the full guide for this method here.

2) No Sew T-Shirt Mask
This method uses just a t-shirt, scissors, pen and ruler. View the full instructions on Runa Ray’s YouTube video.

3) Sewing Machine Required Masks
For those with sewing machines… 2 good mask tutorials come to mind. The first, a simple one (YouTube link), the second – a more advanced design with ties, fitted nose and filter pocket (YouTube link).

Of course, it *hopefully* goes without saying that the level of protection these DIY masks offer is below that of surgical masks and respirators.

If you’ve seen other great DIY mask designs, please share them below in the comments.

What are respirators protecting us against?

Droplets
A primary reason for wearing a respirator is to protect from droplets. For example if a sick person coughs or sneezes when in close proximity to us, the respirator forms a barrier to prevent their bodily fluids reaching our face.

Droplets are generally large, and gravity drags them down to land on objects, rather than staying in the air. So they don’t travel very long distances. There is however research into micro droplets, which get ejected even during talking. This Vimeo video made by Japanese researchers, captures micro droplets on video using high speed cameras. We know large droplets play a role in transmission, but it’s not yet clear what role micro droplets play.

Image from Sui Huang’s blog post on the need for mask usage

Aerosols
What may remain in the air for some time are aerosolized virus particles. So for example, you could imagine someone creating two issues when sneezing, the first are ejected droplets, which travel a short distance, then second, aerosolized virus particles that stay in the air for longer.

Currently there is debate and uncertainty around how long Covid-19 can remain aerosolized, and how much of a risk that vector is compared to others.

What we can do is be aware of what research currently says, and err on the side of caution until its been confirmed.

Scientists at the National Institute of Allergy and Infectious Diseases (NIAID) published a study in NEJM (link) on what can happen under controlled lab conditions. They used a nebulizer, which creates an aerosol from liquids, and tested how long the virus remains measurable in the air whilst aerosolized. They also tested how long the virus was measurable on other surfaces. Their results showed the virus remained measurable for the full duration of the aerosolization experiment; 3 hours. See the graphs below for more details:

This image comes from the NIAID pre-print discussed above, showing the virus titer (viral load)

Dr John Campbell has made a YouTube video discussing this paper in more detail.

Mouth & Nose
Then lastly, whilst the respirator covers our face, it makes it very hard for us to touch an object with the virus and transfer it to our mouth and nose. This is a kind secondary benefit, in addition to the two mentioned above. We just need to make sure we wash our hands carefully as soon as we take the respirator off.

Is Eye Protection Necessary?

Whilst the coronavirus can’t penetrate skin, it can penetrate all exposed mucous membranes, which includes the eyes.

This is why you often see medical professionals wearing eye masks when in contact with infected patients.

That said, eyes are presumably a lower risk as a route of entrance, compared to the mouth, which is constantly breathing air directly into the lungs.

For eye protection, there are two routes that people go down; one is a disposable respirator and safety goggles, the other is a full face respirator. Safety goggles with a rubber air seal provides a tighter air barrier. For example, Bollé make some minimalist models which include a rubber seal, but there are many options available.

Additional Subjects of Importance

Shave! (When Wearing a Respirator)

When wearing a disposable respirator, it is important the wearer has no facial hair around the seal. Bad news guys! 🙁 This 2010 literature review found that “in the presence of facial hair, face seal leakage increases from 20 times to 1000 times“. However, hair under the mask (moustache, goaty, etc) doesn’t cause a problem. See this illustration from the US CDC showing all the permutations of facial hair that are issues and non-issues. The alternative for those who want to keep their beard is to wear a full-face respirator, for which facial hair wouldn’t typically cause an issue.

Important Hygiene Measures

Regular Hand Washing

– The CDC recommend regular hand washing with soap and water for at least 20 seconds.
– Prioritize washing prior to eating and after being out.
– Regular hand washing dries the hands, which at an extreme, may make them vulnerable to infection. To mitigate this, regularly use a glycerin based moisturizer with pump or squeeze mechanism. Those that you scoop are less hygienic.
– A study showed that we touch our face on average 15x per hour. That behaviour may be difficult to change, but if we keep our hands clean, it’s less detrimental.

Image showing the differences in effect between types of hand washing.

Trim Finger Nails

Short finger nails reduce the risk of trapping dirt (and viruses) under the nails. One method to check if your nails are too long is by putting them against your palm. If you can’t feel your fingers but just nails, then they are too long to be kept clean easily.

Alcohol Based Hand Sanitizer

– The CDC recommend that if soap and water are not available, use an alcohol-based hand sanitizer with approximately 70% alcohol. For effectiveness, you need to wait for the alcohol to fully air dry. Interestingly, alcohol contents above 90% are regarded as less effective (source).

Sanitize your phone and other items you touch regularly

– Given how often we use our phones, this seems like the next logical priority to be sanitized. Using antibacterial wipes or alcohol swabs (typically 70% alcohol) to clean your phone and other items is a good option. If the antibacterial wipes claim to be able to kill the flu virus (H1N1) – that’s a good sign they may be able to do similar for the coronavirus. Once finished wiping, leave to air dry.

Other items to consider include:

  • Computer keyboard and mouse
  • House and car keys
  • Re-usable water bottles
  • Car steering wheel
  • Clothing pockets
  • Door handles

And take appropriate caution when interacting with them – sanitizing where possible.

How to maintain a healthy immune system?

We don’t currently have a vaccine, or robust anti-viral medications to tackle Covid-19. In the meantime, we’re reliant upon our immune system to fight the virus. Below we’ll look at steps we can take to maintain it, and put ourselves in the best position, should the “worst case” happen:

Sleep

Get adequate, high quality sleep. For most people ‘adequate’ means 7-8 hours. It’s no coincidence that “burning the candle at both ends” increases risk of illness. A 2004 literature review concluded that “sleep deprivation has a considerable impact on the immune response” and “should be considered a vital part of the immune system”4

Exercise

Exercise regularly, but don’t overdo it. To quote a 2007 study on exercise and the immune system – “moderate exercise seems to exert a protective effect, whereas repeated bouts of strenuous exercise can result in immune dysfunction”5.

Vitamin D

Prior to the Covid-19 outbreak, there was evidence to suggest that:

  • Vitamin D plays a key role in immune function, and, being deficient in vitamin D can make you more susceptible to infection6
  • Vitamin D supplementation protects against acute-respiratory tract infections – as seen in this BMJ meta-analysis covering 25 randomized controlled trials (11,321 participants).

Now that Covid-19 has been around for a few months, we’re starting to see research about vitamin D status as it relates to Covid-19. The two studies below point to vitamin D levels affecting “severity of outcome”, i.e. if someone has low levels of circulating vitamin D, they’re more likely to have a severe illness. As of yet, I haven’t seen any data on vitamin D actually preventing illness. More research needed. For now, let’s look at the research we do have:

  1. An April 9 paper from Mark Alipio in the Philippines (link) that retrospectively analyzed 212 cases of laboratory confirmed Covid-19, and found that with each standard deviation increase in Vitamin D levels, the odds of having a mild clinical outcome, rather than severe was approximately 7.94 times. And the odds of having a mild outcome, rather than critical, was 19.61 times. This paper was discussed in the British Medical Journal here.
  2. An April 30 paper from Indonesian researchers (link) retrospectively analyzed 780 cases with laboratory confirmed Covid-19. They extracted vitamin D status from their medical records, and when controlling for age, sex and co-morbidities, vitamin D status strongly correlated with risk of death from Covid-19. Specifically they said that, compared to normal, those with insufficient vitamin D were approximately 12.55 times more likely to die. Then those who are deficient (less than insufficient) in vitamin D were 19.12 times more likely to die.

Both studies used the same definitions for “normal”, “insufficient” and “deficient” levels of vitamin D:

CategorizationBlood levels of Vitamin D - 25(OH)D
Normal30 ng/ml or higher (75 nmol/L or higher)
Insufficient21 to 29 ng/ml (52.5 - 72.5 nmol/L)
DeficientUnder 20 ng/ml (Under 50 nmol/L)

Whilst we still need more research to confirm these results, it seems the potential upside of maintaining normal (but not excessive) vitamin D levels is high, and the downside is low to zero.

So how do we get enough vitamin D?

Whilst we can get vitamin D from some foods in our diet (for example oily fish, liver, egg yolks), it’s often hard to get enough with these alone. The major source of vitamin D for humans is sunlight (specifically UV-B rays). Without sufficient sun, it’s common to run a deficit on vitamin D. For example, in winter months in the UK, up to 40% of the population are severely deficient (<10ng/ml / <25 nmol/L)7.

If you’re concerned you’re not getting enough sunlight, then supplementing vitamin D is a way to mitigate this.

What is an adequate amount of vitamin D? The National Institutes of Health (NIH) suggest getting 600iu (15mcg) from all sources, per day, for adults. Similarly the National Institute for Health and Care Excellence (NICE) suggest a supplement containing 400iu (10 micrograms) taken daily.

Dr John Campbell has a great video on vitamin D and the immune system . He cites the NICE guidelines of supplementing 400iu per day, but says he personally takes a vitamin D supplement containing 1,000iu daily.

When looking for a supplement, there is evidence to suggest (link) that vitamin D3 raises levels of vitamin D with 1.7x greater efficiency than D2. Examples of NSF certified manufacturers selling vitamin D3 are Life Exension – 1,000iu, Thorne Research – 1,000iu and Pure Encapsulations – 1,000iu.

Selenium

Whilst the evidence around vitamin D status and Covid-19 risk is becoming substantial, I would say that the evidence around Selenium status is still in its infancy. However, I think it’s worth looking briefly. Prior to the outbreak there was already evidence that selenium status plays an important role in immune function. For example:

  • Selenium deficiency increased virulence of RNA viruses such as coxsackievirus B3 and influenza A89
  • Selenium status also mediated effects of HIV10, “epidemic hemorrhagic fever”11 and hepatitis B12

As recently as April 28, an international team of researchers led by Surrey University’s Professor Margaret Rayma identified a potential link between Covid-19 cure rate and regional selenium status in China13. The graph below summarizes the findings quite succinctly, suggesting that higher levels of selenium resulted in higher cure rates from Covid-19. China is a particularly good country to analyze this in because across the country they have both some of the highest, and lowest, levels of selenium intake globally.

The authors note that there are significant limitations to their study, including:

  • Most of their data on selenium status is from 2011 – 9 years ago.
  • Lack of data around age and co-morbidities for cities. Such that demographics make-up will vary, and this hasn’t been controlled for.
  • Lack of info around regional variation in treatment protocols / capacity – which again hasn’t been controlled for.

So whilst the data isn’t robust enough to say that selenium status definitely plays a key role in Covid-19 mortality rate, it’s at least an indication more research should be done.

For a longer review on the paper, see this Surrey University post.

So how do we get enough selenium?

Unlike with vitamin D, where it’s hard to get adequate amounts from our diet alone – with selenium this should be possible. Foods high in selenium include brazil nuts, tuna, sardines, ham, shrimp and more. See Table 2 on the NIH site for a list of food sources. A simple dietary modification could be to add extra brazil nuts to your weekly food intake. Another easy source of selenium are multivitamin supplements that contain selenium. For reference, the NIH Recommended Daily Allowance is set at 55mcg for adults.

Indoors vs Outdoors Risk

Early on during some national lockdowns, there was a conflation of risk between indoor and outdoor settings – assuming both were as bad as each other. This led to some countries prohibiting outdoor access altogether, save for essential trips such as groceries. Not allowing people to get exercise and sun exposure (vitamin D) is likely to weaken their bodies and immune system. Therefore it’s important we update our views as more evidence emerges

Whilst intuitively we might assume risk of transmission indoors is higher, due to poor ventilation, it’s important we combine this theoretical idea with actual studies. Below we’ll look at some of the current evidence:

Indoors

Studies have found high transmission rates indoors, including on cruise ships (National Instatitute of Infectious Disease, 2020), in churches (CDC, May 22) and during indoor choir practice (CDC May 15). The cruise ship example (Diamond Princess) was particularly unfortunate, whereby after detecting a single initial Covid-19 case, and then quarantining everyone aboard the ship, it spread to 712 of the 3,711 people board (19%) (source).

Whilst locations such as cruise ships and churches may be more easily avoided, offices and public transport may not.

A Korean analysis of a call-center outbreak (Emerging Infectious Diseases, April 2020) found that transmission was relatively localized in the office. Despite workers interacting with people in the elevators and lobby, the spread was limited almost exclusively to people who worked on the same floor. Indicating duration of contact was a key facilitator for spread.

Schematic of Korean call center outbreak – blue indicates seating location of infected people

Outdoors

Finding examples of outdoor spread has been less easy than indoor spread. Of course, absence of evidence does not equal evidence of absence.

A Chinese pre-print study (medRxiv, April 7) analyzed 318 Chinese outbreaks involving 3+ people, covering 1,245 confirmed cases in 120 cities. They divided the locations in which the outbreaks occurred into 6 categories: homes, transport, food, entertainment, shopping, and miscellaneous.

It found just 1 outbreak originated whilst people were outdoors. With homes and transport being 2 locations with the most outbreaks.

The analysis was done during winter however, whilst people were spending less time outdoors. A similar study done during warmer months is likely to find a higher incidence of outdoor transmission. Particularly if we bear in mind duration of contact is a key aspect also.

 

Figure from the Chinese study showing location of infections over time

As things stand, we’re still in the early days of research into indoor vs outdoors transmission. As it accumulates, hopefully we can use it to make better risk-based decisions around our behaviour.

Roundup

Hopefully if you’ve stumbled across this article, and you were confused about the difference between N95, KN95 and FFP2/FFP3 masks, this has cleared things up for you.

For Spanish speaking friends who might find this article useful, it’s translated here.

If you have any further questions, please leave them below in the comments.

Further Learning

For preventative measures you can take as an individual (which also benefits the collective) see this short list of videos by Dr John Campbell:

Dr John Campbell on YouTube

Post Change Log

Given that the situation with Covid-19 is evolving rapidly, I’ve decided to add a Change Log for this post. It will list changes I’ve made from May 12 onwards.

See Post Sources Below:

  1. N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care Personnel – A Randomized Clinical Trial – Lewis J. Radonovich Jr, MD et al. – JAMA – Sept 2019
  2. Surgical Mask vs N95 Respirator for Preventing Influenza Among Health Care Workers – A Randomized Trial – Mark Loeb et al. – JAMA – Nov 2009
  3. Face Mask Use and Control of Respiratory Virus Transmission in Households – MacIntyre et al. – Emerging Infectious Diseases Journal – Feb 2009
  4. Sick and tired: does sleep have a vital role in the immune system? – Bryant et al. (2004)
  5. Exercise and the Immune System – Brolinson (2007)
  6. Vitamin D and the Immune System – Cynthia Aranow (2011)
  7. SACN – Vitamin D & Health – UK Government Report (2016)
  8. The influence of selenium on immune responses – Hoffmann and Berry (2008)
  9. Host nutritional status: the neglected virulence factor – Beck et al. (2004)
  10. High risk of HIV-related mortality is associated with selenium deficiency – Baum et al. (1997)
  11. Inhibitory effect of selenite and other antioxidants on complement-mediated tissue injury in patients with epidemic hemorrhagic fever – Hou (1997)
  12. Protective role of selenium against hepatitis B virus and primary liver cancer in Qidong – Shu et al. (1997)
  13. Association between regional selenium status and reported outcome of COVID-19 cases in China – Rayman et al. (2020)
John

Posted by John

Note: Not a Medical Doctor or PhD. I'm a researcher and writer, with a focus on the subjects of health and longevity. My intent is to write about scientific research in an accessible, understandable way. If you believe something I've stated needs a reference, and I haven't done so, please let me know in the comments. Follow on: Twitter

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203 Comments

  1. Avatar
    Kevin Langley June 3, 2020 at 4:07 pm

    Great information John. If you don’t mind, I’m going to post this on my blog (just starting it at universalprotectiveproducts.com). I should have this copied there sometime today or at least have a reference back to your page.

    A lot of folks believe that wearing a mask / face covering will keep them safe. Your explanation that it might be safer than zero face covering is spot on. There is very little proof that wearing a typical 3-layer face mask will provide protection for the wearer, much less a cloth mask.

    If people are trying to protect themselves AND others it should be noted that many “N95”, “FFP2″,”FFP3” or “KN95” respirators are just plain fakes. They may have a layer of blown material, but the rest is often cotton. Folks should look out for the fakes. Likewise, the 3 layer masks may also be missing a layer of melt-blown material. We always take a lot of precaution selecting products. The wrong selection for a medical or other front line worker could mean the loss of many lives.

    For those who don’t have a surgical / medical 3-layer mask or N95 / KN95 / FFP2 / FFP3 respirator mask (the real kind), the cloth is also a viable option to protect others, but again, it does not protect the wearer. Here’s a bit more info from the Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/coronavirus/in-depth/coronavirus-mask/art-20485449

    Thanks again for the great information.

    Reply

  2. Avatar

    Congratulations on this excellent article. He’s been very helpful! It turns out that the article on how to sanitize respirators was also helping a lot. Why was he removed from the site? Can I get it or consult it elsewhere? I appreciate it very much if you can help, John.

    Reply

    1. John

      Hi Lupa. Basically, that information is changing constantly, and I haven’t had time to keep it updated. It’s a very sensitive subject, in the sense that it can have a big impact on someone’s health if they do it right, or wrong. Thus I really don’t feel comfortable having the information up unless I’ve had time recently to go over it with a fine tooth comb. In the absence of that article, I can suggest the N95Decon site as an alternative source of information. Hope that makes sense!

      Reply

  3. Avatar

    First, thanks so much for a great article. I’m so glad I stumbled on it.

    I hope you can answer some questions I have about mask standards, which I have even though I’ve spent countless, countless, hours reading about masks.

    I recently bought some surgical masks (for $2 each) and when I got home from the medical supply store, I saw that the box says “BFE95”. When I googled that term, and learned about BFE and its various standards. I also then discovered PFE, which my masks are not. Before that, I had read hours and hours about masks and had never seen BFE or PFE. After that, I spent hours more trying to learn more.

    Yesterday I found a website selling surgical masks that are FFP2. But I thought FFP2 is the same as N95 and KN95, and if that’s true, then a surgical mask can’t be FFP2 — as surgical masks look nothing like the others which are much thicker and fit more tightly. The website has photos showing a surgical style mask and implies they’re PFE of some percentage. It says: “Satisfies FFP2 standard, EN 149:2001+A1:2009 standard. Quality 3-layer design: outer water-resistant layer blocks larger droplets, middle melt-blown layer filters out more than 95% of bacterial and particulates, inner soft layer makes it comfortable to wear.” Is it possible that these surgical masks can be FFP2? PLus, they’re only 40 cents each, which sounds too good to be true, but the company seems to be reputable from what I can figure out. Sine Trading International.

    So many articles use the generic term surgical mask, but I’ve learned that there are so many different kinds, meeting different standards, now whenever I read an article, I’m so confused b/c I wonder what types of surgical masks they’re talking about.

    Reply

    1. John

      Hi Cindy. That fits with my current understanding also. As far as I know, BFE & PFE measure the efficacy of the materials used at blocking certain particle sizes. They don’t however account for the overall efficacy of the surgical mask itself at blocking particles, which would be hampered by the air gaps around the edges.

      Then in terms of an FFP2 rated surgical mask, I don’t believe that can exist. The FFP2 standard has a maximum limit for “Total Inward Leakage” of 8%. Given the lack of a tight facial seal on a surgical mask, it would not be possible to meet this standard of maximum total inward leakage (I think).

      Let me know if that helps.

      Reply

      1. Avatar

        THanks John. Every time I say I’ll stop researching masks, I see something else and start again. My head is about to explode. In spite of probably over 20 hours of reading, I still feel so confused, and dont’ know if it’s me or that the articles are truly contradictory.
        And dont’ know if it matters anyway.

        I thought that ad seemed off by advertising a FFP2 surgical mask. And the 40 cents each price also sounded too good to be true.

        Does the term “surgical mask” mean anything, given all the different ratings? Like, mine are BFE95 but others are BFE & PFE ? So, if any article discusses “surgical masks” w/o more info, how are readers to interpret that?

        Also, I just saw an ad for a cloth mask which uses PM 2.5 filters and googled that term but still am at a loss at that. That ad claims that the mask is equivalent to N95. Can it be ?

        Many thanks for your efforts.

        Reply

        1. John

          Hi Cindy.

          That’s a good point around “what is the definition of a surgical mask” – given there is clearly variance in specification. Have tried to give some guidance on that subject in the article, but will reflect on how I could improve that further. To my knowledge the major factor that varies is the quality of the melt blown filter that gets used. Particularly the thickness used, but there’s more to it than just that I think.

          The 80/20 of a surgical mask is a melt-blown layer sandwiched between 2 non-woven fabric layers. Which is simple enough.

          Regarding a cloth mask which uses PM2.5 filters… and is that N95 equivalent? Probably not.

          For example PM2.5 refers to filtering particles down to 2.5microns, but that doesn’t tell us what % are filtered.

          N95 is filtering at least 95% of particles down to 0.3microns.

          Hope that helps a bit.

          Reply

    2. Avatar
      Kevin Langley June 3, 2020 at 5:00 pm

      Cindy, all great points. First, a 3-layer surgical mask should never cost anywhere near $2.00. That is outrageous. Surgical Masks are Rated under the ASTM standards. There are 3 Levels that include testing of Fluid Resistance
      Differential Pressure (Delta P)
      Bacterial Filtration Efficiency (BFE)
      Particle Filtration Efficiency (0.1μm PFE)
      Flammability. Go here to read more.

      No matter which ASTM Level is used a mask worn incorrectly can invalidate its use. Surgical 3-layer masks should be worn with:
      – metallic wire should sit right above your nose bridge
      – inner and outer surface cannot be distinguished from their colours
      – folds should go downwards for the outer surface!(folds on your mask will become a container for droplets, bacteria and viruses otherwise)

      Nelson Labs has a chart here (https://www.nelsonlabs.com/wp-content/uploads/2020/03/Face-Mask-Testing-Requirements.pdf) that shows the differences for the 3-layer masks, but again the question is are you wearing a mask to protect yourself or others.

      Another topic mentioned is the differences between 3-layer and respirators. FFP (Filtering Facepiece), KN95, and N95 are all types of respirator masks. The 3-layer masks are not respirators. The FDA recently allowed that respirators that have approval from regulatory agencies and standards from other countries can be used in the US for similar circumstances (civil or medical depending on the certification). Here is a comparison chart of the various approved respirators that may act as protection for the wearer from disease. This chart is from 3M, maker of NIOSH approved N95 masks. https://multimedia.3m.com/mws/media/1791500O/comparison-ffp2-kn95-n95-filtering-facepiece-respirator-classes-tb.pdf

      Respirators are not 3-layer or 4-layer type surgical masks.Though they are layered, they are a completely different face covering with a different purpose. For self protection, the best way to go is with a respirator. However, be certain that the respirator is not woven cloth, such as cotton.

      Reply

  4. Avatar

    I am a doctor and for me this is the best article I have read about this topic. Thanks very much John

    Reply

    1. John

      You’re welcome, thanks for the message!

      Reply

  5. Avatar

    Thank you a lot. Brazilian retired physician.

    Reply

  6. Avatar

    In the EU and UK we are having an issue with equipment marked as being to the Correct Standard but the supporting certificates are fake. The European Safety Fédération has information on its website around fake certificates:

    https://www.eu-esf.org/covid-19/4513-covid-19-suspicious-certificates-for-ppe

    Reply

    1. John

      Great list, thanks.

      Reply

  7. Avatar

    Really useful article with some interesting points to consider, The Health and Safety Laboratory in the UK published a Resource Report: Evaluating the protection afforded by surgical masks against influenza bioaerosols. Gross protection of surgical masks compared to filtering facepiece respirators Prepared by the Health and Safety Laboratory for the Health and Safety Executive 2008:

    Main Findings

    This study focussed on the effectiveness of surgical masks against a range of airborne particles. Using separate tests to measure levels of inert particles and live aerosolised influenza virus, our findings show that surgical masks provide around a 6-fold reduction in exposure. Live viruses could be detected in the air behind all surgical masks tested. By contrast, properly fitted respirators could provide at least a 100-fold reduction.

    Recommendations
    In principle, surgical masks that are worn correctly should provide adequate protection against large droplets, splashes and contact transmission. They may also reduce to some degree any residual aerosol risk, although this level of protection might not sufficiently reduce the likelihood of transmission via this route. Consequently they should not be used in situations where close exposure to infectious aerosols is likely.

    Full report at:

    https://www.hse.gov.uk/research/rrpdf/rr619.pdf

    Stay Safe Everyone 🙂

    Reply

    1. John

      Thanks for summarizing and sharing this! Very helpful.

      Reply

  8. Avatar

    About valves. I don’t know exactly how they work but wonder if they put the wearer at risk as well as others, the latter as you explain?
    IF it’s the case that the valve opens through pressure from the wearer’s breath, then could not a simultaneous but larger pressure from someone coughing in the wearer’ vicinity cause the virus to enter the valve?
    As I say I don’t know if this is how they work but was an added reason I didn’t buy a valved mask just in case.
    Thank you for your article which guided me as to which kind of mask to buy.

    Reply

    1. John

      Hi Barry. Respirator valves are one-way typically. They will open to a wearer’s outbreath, but are forced closed by air coming from the other direction.

      Reply

  9. Avatar

    Thank you for the work you put into this. I’m in Tech Ops Safety for a large US airline and I’ve been searching for information on this subject. Very informative and well researched. Kudos.

    Reply

  10. Avatar

    Hi john,
    I was searching to know about the differences between the masks And the materials. accidentally, I saw the article and it was very very helpful to me . Great job, thank u so much

    Reply

  11. Avatar
    Omkar eswara babu Danda May 2, 2020 at 6:08 am

    Thanq for detail explanation
    may i have this article in pdf format plz?

    Reply

    1. John

      If you can make it yourself, you’re welcome to.

      Reply

  12. Avatar

    how to cite the information mentioned in the page?

    Reply

    1. John

      However you want to, no special requirements.

      Reply

  13. Avatar
    David Walters, Ph.D. April 26, 2020 at 3:40 pm

    Absolutely fantastically informative article on PPE for the current viral pandemic. I’m not unlearned in these areas. But I learned a great deal from this article and, especially, from the provided references.

    I’ve sent a link to this article to at least two dozen colleagues and to > 100 neighbors and friends both nationally and internationally.

    I was particularly impressed with the discussion of filtration capabilities of the masks / respirators and, most importantly, the difference between airborne particle sizes and the size of the virus itself. You cleared up a number of questions in my mind.

    Thanks John.

    With gratitude and respect,

    David W. Walters, Ph.D. (retired but with 40+ years working in applied clinical science and research including molecular biology and genetic engineering).

    Reply

  14. Avatar
    José Tomás Domínguez April 23, 2020 at 7:47 pm

    Great article, I was just researching which kind of N95 masks where better, if the ones with valve, or without.
    Do you have any reference, from studies, or papers that validates this argument?
    I definitely agree with you, but I must show evidence of this, and haven’t been able to find.

    Reply

    1. John

      Hi Jose. No, I haven’t seen a paper/study on this, it was just an (obvious?) observation, once I reflected on it. Also, as point of reference, the 3M USA page for *surgical* masks and respirators (link) doesn’t include any with valves. Which makes sense, as they need to protect the patient from their germs.

      Presumably an easy experiment one could do is take a puff of a cigarette or vape (nicotine free), don a valved respirator, and visually see how much smoke is emitted through the valve on outbreath. Then repeat the experiment using a valve-less respirator.

      Reply

  15. Avatar

    Excellent research! Thank-you!

    Reply

  16. Avatar

    This article was super useful and helpful … thank you 👏👏👏

    Reply

  17. Avatar

    When someone posted this link I thought “fastlifehacks.com, meh, that sounds like some buzzfeed lightweight bs”.
    Thankfully I opened the link and read through the article and I think it’s great. It really is a nice writeup with lots of useful links. Very well done.

    Reply

    1. John

      Haha, that made me laugh. Yeah, the name is a bit of a misnomer, given that these posts are anything but fast. I’ve a habit of making things a bit long 😊 Thanks for the comment, and glad the article was of use.

      Reply

  18. Avatar

    Very detailed and informative. If only people will be able to read this very helpful article.

    Reply

  19. Avatar

    If there are no n95 and only r95. Is it still safe to use it in the hospital?

    Reply

    1. John

      Hi Rog. As far as the specifications go, R95 should in theory have the same particle filtering capacity as an N95 mask. Where the N is “Not Resistant to oil”, the R is “Somewhat Resistant to oil”. The oil resistance being the key difference between “N” and “R”. Whether or not it is *safe* for use in hospitals is another question. It won’t be the “R” part that is an issue, but there is more to making that qualification, and it should be left up to the subject matter experts at the hospital. Just as an example, you’d want to make sure it comes from a trustworthy manufacturer, and you’ve tried on a few in the batch to fit test and check for defects.

      Reply

      1. Avatar

        Nah, the only difference is it was “FDA approved” v. NIOSH approved. The one you can use at hospitals was “FDA approved” and we all know how red tapes work. Just because it was approved by the FDA doesn’t mean it’s less efficient at protecting you from 0.3-0.1 micron particles, which is what the R95 was certified for by NIOSH.

        Reply

  20. Avatar

    Hi, Jon
    Thank you very much for a great one stop information. Really enjoyed reading it👍👍👍

    Reply

  21. Avatar

    Thanks so much for your post!!!!!!!!!!!!

    I learned so much!

    The one thing I didn’t see was a comparison between masks vs. N95 respirators with valves regarding which protects OTHER people better. Since those are the only choices I have, I like to know which to wear to protect both myself and other people.

    Reply

    1. John

      Hi Marv. Whilst I haven’t seen a study for this, It would appear (?) that a mask will protect others better than a valved respirator. The valve on the respirator means that much of the out breath / cough / sneeze will make its way out into the air without any filtration. If the valve is on the front, that may be “worse” than if it’s on the side, but neither are great. At least with a surgical mask the vast majority of droplets will be blocked from spraying into the air.

      The more I’ve thought about valved respirators in the context of a respiratory virus, which is what we have now, the less I like the idea of them. Specifically because they don’t protect others from the wearer. However for construction work/DIY – they’re great.

      One thought with a valved respirator could be to wear a mask over the top of it to block droplets escaping? It could be a viable trade-off if one feels they have need for a respirator, and only has access to valved versions. Although of course it’s not perfect.

      Reply

      1. Avatar

        As an experiment, tried blowing raspberries through my valved N95 onto a sheet of paper, and the paper remained dry. So a valved N95 does afford some protection?

        Reply

        1. John

          Hi Matt, thanks for the message. Maybe some, but is it adequate? That’s the question. I’d hypothesize no, but would like to see some research on it to know for sure.

          Reply

  22. Avatar

    Absolutely excellent and decent work. Thank you. Greetings from Poland.

    Reply

  23. Avatar
    Eugene V. Flynn April 13, 2020 at 6:46 pm

    Really excellent work. Clear and concise. Fantastic graphics. May I have permission to incorporate some of your work (with credit) in a household guide I’m preparing for family and friends? Happy to send you a pdf file when completed.

    Reply

    1. John

      Hi, yes, no problem at all 🙂

      Reply

  24. Avatar

    Great article, from Electronic Engineer in Sweden

    Reply

  25. Avatar
    Mustafa Cuneyt Gezen April 13, 2020 at 4:17 am

    Greaaat article. Thank you from an industrial hygienist in Istanbul, Turkiye.

    Reply

  26. Avatar
    Dr. Nguyet Tau April 10, 2020 at 9:32 pm

    Great and comprehensive! Thank you from a pediatric dentist in the USA

    Reply

  27. Avatar

    Dear John,
    I really appreciate your efforts to summarize this great article! I finally understand those seemingly complicated facial masks!
    That’s really helpful!
    Many thanks!

    Reply

  28. Avatar
    DR. FRANCESCO LAURITANO April 9, 2020 at 4:18 pm

    GREAAAAT JOB…THANK YOU FROM AN ITALIAN ORAL SURGEON IN BARCELONA!

    Reply

  29. Avatar

    I am a doctor at a hosp in Pakistan and I didn’t know much about masks . Thank u v much for such a thorough article .
    Dr Amir

    Reply

  30. Avatar
    Gareth Harvey April 8, 2020 at 1:43 am

    Great article. I had a pack of ffp2 respiratory that I used as protection in the building trade. After asking around no one seemed to know if they were of ANY use in today’s crisis, but the general opinion was that they were useless. Thankyou for your article and for giving me a definitive answer.

    Reply

  31. Avatar
    DR. ERSKINE FENTY April 5, 2020 at 6:29 pm

    Totally appreciated this article. I have been looking at getting my own respiratory face covering and had already settled on ordering an Eclipse unit and then I spotted this article which confirmed that I had made a good decision. thank you.

    Reply

  32. Avatar

    Great article, as HCW, I’ve been looking for this info for long time, difficult to make sense from what is around in the internet.. Thank you so much for helping out..

    Reply

  33. Avatar

    Great article. Just what I’ve been looking for. I wish the news would offer more guidance to articles like this.

    Reply

  34. Avatar

    Amazing article, thanks for raising awareness.

    Reply

  35. Avatar

    Extremely thorough and evidence based article John, and extremely useful under current circumstances too! I am a doctor in Greece and this article has cleared up a lot, especially for the usefulness of surgical masks which pretty often is the best we have…
    Congratulations and thanks!

    Reply

  36. Avatar

    Exceptional article, also under lockdown in South Africa. Sharing immediately with all my friends. Thanks very much for this, John 🙂

    Reply

  37. Avatar

    Greetings from South Africa (where we are on day 6 of a 21 day lockdown), and thank you for an extremely comprehensive and well constructed write-up!
    We use FFP-rated respirators here (loosely referred to in SA as dust/particle masks), so this has been a great help considering a large chuck of our inbound international news refers to N-rated respirators.

    Reply

    1. John

      Hey Tim! Thanks for the message. Glad the article helped clear up some things. Wishing you well during your lockdown 💪🙏

      Reply

  38. Avatar

    Thanks so much, this is the most comprehensive and practical guide I have read anywhere so far. Shame on the news media which have not done enough of this type of information distribution but spending majority of the air time sharing opinions and spreading fear by speculation.

    Reply

    1. John

      Thanks Slingshot! Lots of great work coming from all directions to try and tackle this problem. Keep it up and we’ll get there 🙏

      Reply

  39. Avatar

    Hi John, This really is a great tool for people of all walks. I am not qualified or experienced enough to comments on the not PPE areas such as Vitamin D etc. Is there a way to post all this up as a PDF or are you happy for us Neanderthals to copy and create our own version. Thanks

    Reply

    1. John

      Hi Ivan. Yes, absolutely, feel free to copy this and create your own version. We don’t have time right now to be precious about that sort of thing, so feel free to work away.

      Reply

  40. Avatar

    Considering placing orders for KN95 respirators using China sources. Concerned about counterfeits and lack of NIOSH approval. And, some of the KN95s are industrial and not medical grade. Looking for several hundred thousand. Any thoughts/suggestions?

    Reply

    1. John

      Hi Tom. Based on the 3M document I linked to above, the N95 and KN95 specification appear similar enough that it shouldn’t a concern (for example see the comparison table).

      Indeed, 3M say “Based on this comparison, it is reasonable to consider China KN95, AS/NZ P2, Korea 1st Class, and Japan DS FFRs as “equivalent” to US NIOSH N95 and European FFP2 respirators, for filtering non-oil-based particles such as those resulting from wildfires, PM 2.5 air pollution, volcanic eruptions, or bioaerosols (e.g. viruses)”.

      As you point out, I imagine the bigger concern is that the Chinese manufacturer delivers what they say they will, and indeed the respirators meet the specifications. Perhaps it’s possible to find an inspection company who can do the appropriate quality checks to verify – which would allay that concern.

      Reply

      1. Avatar

        Thanks for your reply. I’ve been provided the FDA Registration Certification dated 3/20/20 and the CE Documentation Review for the mask so feel pretty good.

        Reply

      2. Avatar

        John, Thanks. Do you know what the differences are between a KN95 Class 1 and KN95 Class 2 respirator? I have offers on each but not clear what the differences are.

        Reply

        1. John

          Hi Tom, apologies, am unclear what the difference would be between KN95 class 1 and 2 is. Have seen FFP2/P2 referenced before as “class 2”. However that doesn’t make sense in this context, because KN95 should always be equivalent to FFP2/P2 – based on what I understand of the specification.

          Reply

          1. Avatar

            Thanks a lot for you,
            Unfortunately When I found some statements about features of respirator like dust particles, Does it mean we can not use it in the medical field?
            And what you mentioned about 3m respirator 8812 filter less than 0,3 size, I couldn’t find this type in the CDC NOISH approved list, What is your opinion?

          2. John

            Hi Ahmad. Have you found an N95 version of the 3M 8812? I can only see the FFP2 version (here). NIOSH are the American organization who set the N95/N100 standards. Whereas for European approved respirators they use FFP rating. It looks like the 8812 is FFP2 rated for use in Europe, so I wouldn’t anticipate to find it on the NIOSH website.

      3. Avatar

        Some masks manufactured in China have British Standards Institution (BSI) certification. BSI is a Notified Body and its code after the CE mark is 0086, so google “CE 0086” AND “FFP3” in China (using Google Advanced Search).

        BSI has the ‘VerifEye’ directory. Google: verifeye directory bsigroup.

        Reply

  41. Avatar

    hi really useful round up thanks. see also research from uk’s HSE re masks v respirators for flu virus. Very thorough and informative. HSE contract research RR619, just google it.

    ta jim noonan

    Reply

    1. John

      Thanks Jim, found the research – will take a look at it and see how to weave it into the article. Thanks again for taking the time to write and inform us. Had no idea that research existed.

      Reply

  42. Avatar

    Nice work John! More information here than offered to HCW in their hospitals! I will be using this to educate colleagues! Stay well; we are all scared with the scale of this thing!

    Reply

  43. Avatar

    I see several questions, not only on this page but other pages from healthcare workers regarding the multiple usage of masks due to shortages; and how to ‘safely’ clean them for re-use.

    Could a possibility for this to be to use dry sterilization using high concentration ozone gas in a sealed plastic tub?

    Ozone kills virus particles but is also very harsh on rubbers and latex.

    On one of the 3m links posted below there was a portion that specifically stated the the N95 masks contained no natural rubber or latex portions which would be degraded by ozone gas.

    I know the US has an aversion to using ozone gas as it is toxic, but seems like it could be a viable alternative for re-sterilizing these masks for multiple uses.

    Reply

    1. John

      Hi Matt. No experience at my end on ozone usage, so can’t add anything valuable to this. But this post is getting a good # of eyeballs, so maybe others will read and add value.

      Same topic, but different technique, this article discussed a hospital in Nebraska have setup a room with UV lamps to radiate respirators they hang in there (NY Times article link).

      Reply

    2. Avatar

      Hi, Regarding of reusage of respirator, Can We use UV machine to sanitize the respirator and make it multiple use for more than one staff or dedicated for same staff?
      Thanks

      Reply

      1. John

        Hi Ahman. Regarding the use of UV, the section on UV-C in this post I wrote yesterday may be of interest. It looks at work done by Nebraska Medical, setting up and documenting their UV-C system for decontaminating respirators to allow for safe re-use. If you want to replicate something similar to it, their PDF I’ve linked to gives some solid details on their process.

        Reply

  44. Avatar

    It appears the ASTM Level 3 masks fall below the filtration of the N95/FFP2&P2 masks.

    Would you think a ‘fair’ comparison of these masks would be the FFP1 & P1 masks?

    Are there any direct comparisons?

    Reply

    1. John

      Hi Matt. Thanks for your comment. Prior to this I’d only looked at ASTM for N95 masks (so fluid protection for respirators). Didn’t realize there ATSM level 3 surgical masks. If I find anything concrete on their efficacy improvement vs regular 3-ply surgical masks I’ll add another comment.

      Even comparing against FFP1/P1 respirators would miss the fact that the face-fit is not tight, and there are still big gaps around the edge of the face (due to the nature of surgical masks). But when we’re caught in a pinch as we are currently, for sure better than nothing.

      Reply

  45. Avatar

    Good evening, guys. I have a question. Respirators may protect us from 95% to 99% of viral particles that could enter our body. However, I wonder whether this works for the Coronavirus. If our bodies don’t have the antibodies to protect us against this virus, then doesn’t it mean that any virus particle that enters the body will spread inside us since our bodies can’t fight it?

    Reply

    1. John

      Good question. It’s my understanding that we have not tested the science to the point where that question is answerable (precisely) yet. That said, my current understanding is that this is a probabilistic thing. Using no respirator increases your probability of contracting the virus via droplets or aerosol. Vice-versa, wearing a respirator dramatically decreases your probability of contracting the virus via these methods.

      The best thing one can do is social distancing, however in situations where that’s not possible, respirators have their place.

      Reply

    2. John

      Something that caught my eye today on this topic…

      Peter Kolchinsky on Twitter talked briefly how the immune system works better if the infection starts with a low dose (link), because the virus has to divide more times to get to a high dose, buying time for the immune system to function.

      Reply

  46. Avatar

    Hi. How long can one wear the FFP2 mask after using it?

    Reply

    1. John

      Hi Yasine. Strictly speaking, if it’s a disposable respirator (of any specification), they are single use. In practice many medical professionals are having to re-use respirators for multiple days due to shortages. Some people are choosing to try and “disinfect” their respirators by washing or spraying with chemicals. The risk with this is that you damage the filtering capacity, and I have not seen any official guidance on how to do this safely.

      If respirators do get re-used, then it’s especially important to avoid touching the front with your hands, where possible. If you do, then it’s important to wash your hands after, because the respirator effectively becomes a biohazard over time.

      Reply

      1. Avatar

        Great question on re-use and extending the use. Is there any manufacturers recommendations on how long you can wear the Respirators. If I was working a 12hr shift in an ICU with COVID-19 patients, is this okay or am I supposed to change it out after a specific period of time. I appreciate that if it gets too moist or damaged, then it will have to be changed. Great work and super links too.

        Reply

        1. John

          Hi Ivan, I’ve got some updates in the pipeline around respirator re-use, in terms of santitizing the respirators after use, so that they can potentially be re-used. Obviously under ideal scenarios they’re single use – but we’re not in ideal scenarios right now. So if it’s the choice between not having one to use, and re-using one, we are forced to be resourceful.

          With regards to the duration of use in ICU – I would probably refer to the CDC guidelines on this (link here). They provide quite a few scenarios where they suggest to discard the respirator. For example “if contaminated with blood, respiratory or nasal secretions, or other bodily fluids from patients” – which makes sense. Also after “aerosol generating procedures”, which presumably intubation is. With the latter, you’ve got to wonder if there’s enough PPE to make this viable. Anyways, maybe you can check through that document and see what’s applicable or not.

          Reply

  47. Avatar

    Thanks so much for this informative and well written post.

    John Bierly, MD

    Reply

    1. John

      Thanks John!

      Reply

  48. Avatar
    Patrick Murphy, DO March 18, 2020 at 3:13 pm

    Thank you very much, like most physicians, I didn’t know the specifics of masks/respirators. I will immediately apply this.

    Reply

  49. Avatar

    Best article right now about this mask madness.
    Also, in China KN95 = ffp2, so at the end Covid-19 protection is almost the same with mask with ffp2 and ffp3? Even less grade masks?
    Thanks

    Reply

    1. John

      Hi Alberto, yes KN95 is approximately similar to N95, which is approximately similar to P2 & FFP2 in terms of filtering capability.

      Was that what you were asking, or were you asking something else?

      Reply

    2. Avatar

      FFP3 is higher grade mask.

      Reply

  50. Avatar

    Good morning. Excellent text. Am i allowed to use some parts for Facebook?

    Reply

    1. John

      Thanks, yes, you’re welcome to.

      Reply

  51. Avatar

    If the surgical is one-way to protect the patient. Will wearing the mask inside out (the blue/pink side towards the wearer) be able to effectively protect wearer?

    Reply

    1. John

      Hi Stephen. The reason that surgical masks are generally thought of as protection for the patient only (and not the wearer), is that their 3-ply material doesn’t have high filtration capability compared to P3/N100, and additionally there are the air gaps around the sides. So it’s mainly for catching droplets from the wearer when they talk/cough/sneeze. However, if you look at the research above, you will see there *appears* to be some efficacy when it comes to protection from influenza, compared to no mask. They didn’t reverse the masks for this, they just wore them normally.

      Reply

  52. Avatar

    Great technical reference John! One thing that I’ve questioned however, is the assumption that respirators offer “two-way” protection. Many of the higher efficiency masks have breather valves built into then which allow exhaled air to escape unfiltered and with much less restriction than the air that is filtered while inhaling. Your pictures show many of them with the small square at the center of the mask.

    With this in mind, the concept of using the masks to protect those around you from your own exhaled air might be significantly less effective.

    Do you have any thoughts on this?

    Reply

    1. John

      Hey Jim, that’s an excellent point, and one I hadn’t thought about, thank you. You’re spot on, the valves mean that a lot of air escapes without filtering. This is great if you’re in a scenario where you want to filter the inflow, but aren’t worried about the outflow. For example, maybe if you’re doing building work. In situations where we potentially want to protect others, this is non-optimal. In that light I’ve adjusted the article to reflect this. Any further suggestions, do let me know.

      Reply

      1. Avatar

        Thank you for the well written documentation John. Regarding this one-way flow of P100 respirators. Excuse my ignorance, I’m not a medical professional. Just a citizen concerned for my own health and that of others. Do you think wearing a surgical mask inside a half face mask or full face mask respirator could prevent those droplets from infecting others while maintaining the protective advantages of these higher end P100 respirators? Of course, assuming the respirator maintains a good seal around the face and the surgical mask’s strings does not break that seal.

        Reply

        1. John

          Hi David. I agree, using a surgical mask is a possible “hack” if you’ve got valved respirators, and want to block coughs/sneezes from the wearer. Of course ideally one uses a non-valved respirator. But right now these are not ideal times, so we’re having to work with what we’ve got.

          You’re probably right that wearing the surgical mask inside the respirator is the safest option, but I could imagine that being quite uncomfortable and hard to breathe through. Putting it on the outside might be more comfortable, but less efficient.

          Reply

          1. Avatar

            Agreed, also, putting some N95 filter material on the outside of the valve will help this.

  53. Avatar

    Hi John,

    Thanks for a great article trying to put together many aspects of mask/respirator. Please note that FFP3 is on par with N99, it is way below N100. P3 is different from FFP3. Below are a list of links might give you more info on this topic:

    Here is a link from 3M:
    https://multimedia.3m.com/mws/media/1313143O/respirators-for-protection-agains.pdf

    Two Wikipedia links:
    https://en.wikipedia.org/wiki/Respirator#European_norms
    https://en.wikipedia.org/wiki/NIOSH_air_filtration_rating

    A link from USA CDC:
    https://www.cdc.gov/niosh/npptl/topics/respirators/disp_part/default.html

    Cheers,
    Haiyang

    Reply

    1. John

      Hi Haiyang. Great point, thank you for taking the time to comment and provide constructive feedback/help. Have updated the post with this information 👌

      Reply

      1. Avatar

        Hi, is Fpp3 mask washable?

        Reply

      2. Avatar

        Thanks for the feedback, John. I wish I had the energy to put together such good article like yours, I’ve done my own research to understand it, but do not have enough energy/skills to write about and share and support. I hope with this piece of accurate information entering your article, your article will be able to help more people. The people deserve more comprehensive articles like yours to tell them what to do/what to choose in this unfamiliar territory. Take care and stay well!

        Reply

  54. Avatar
    Dmitry M from Russia March 14, 2020 at 7:59 pm

    1. I used very simple test to visualise the difference between surgical P1 mask and P3 respirator. I light a sigarette and pass smoke from my mouse through both types P1 & P2. P3 is MUCH better – practically no smoke out. You can repeat it if you have spare mask. I did not destroy P3 mask, I used P3 filter element for this test. BIG difference!
    2. Old industrial respirators for gas protection are very cheap and stil availble (at least in Russia). Their filter element (coal powder) can be replace with anti-aerosol element from other respirators. I can show foto, but I don’t know how to add it to the comment

    Reply

    1. John

      Interesting, thanks for sharing Dmitry. RE photos, I don’t think this wordpress comment system allows for them. That said – you could host the photo on ImgBB / Imgur etc, they hyperlink to it in your post.

      Reply

    2. John

      Btw, how are the numbers in Russia currently? One of the trackers I follow (BNO News) has them down at 59 confirmed cases, zero deaths. Which is very good compared to lots of the rest of the world. Does that sound accurate based on being in the country?

      Reply

      1. Avatar
        Dmitry M from Russia March 14, 2020 at 9:26 pm

        Yes, current number is low – 59. But we will not avoid significant spread in next weeks. New actions announced today, hope it will help to postpone the process.
        More words about old-style respirators – my idea was to find cheap and available replacement for normal modern P3 models which will dissappear soon. Old one cost nothing (<4USD) and have very simple filter construction (cylinder box with cover). So it is very easy to open it and replace filter element. Or you can buy filters with anti-aerosol element like A1P1 (2USD), remove coal and use only anti-aerosol filter from it. I suppose that this old models we were produced in millions units during cold war to protect population from radioactive dust. Probably you have same old models in your country.
        Last comment – disposable P3 is very uncomfortable vs plastic P3 respirator (difficult to breathe due to high air resistance – less filter area).

        Reply

        1. Avatar
          Dmitry M from Russia March 14, 2020 at 9:39 pm

          mask foto – link

          anti-aerosol element to add – you can put 3! elements in the box – link

          or better element – link

          Sorry for long links. Probably you have same models in your country in old amunition shops.

          Reply

          1. Avatar

            Dimitry, what your doing is a very good idea but remember that when putting the new filter in, you can’t have any gaps. Air will travel the easiest way so it may bypass the filter elements if your not careful. This is the reason the are not really doing such thing on a large scale.

  55. Avatar

    Thank you so much John for this useful and very clear information.
    I’m italian, and you can understand how we feel and live this argument.
    So I would ask your permission for translate and spreading to our citizen. Obvously quoting source of information.

    Best regard
    Davide

    Reply

    1. John

      Absolutely Davide, please go ahead.

      Reply

  56. Avatar

    Hi John,
    Thank you for your highly informative and helpful article.
    I have a question about boosting FFP2 mask efficiency.
    If we placing a surgical mask on FFP2 does it increase the filtering efficiency?

    Reply

    1. John

      Hi John. I would presume so – as it adds extra layers. It might make breathing harder though. How much would it improve filtering? I’m not sure – I haven’t seen any studies testing this.

      Reply

  57. Avatar

    Thank you so much for such an informative article. I’v recently purchased some FFP2 masks. I am sorry this may sound a bit silly. I noticed there is thin disk inside round plastic nob on the mask, but there is quite a big gap I can see. How can the air be filtered when there is a gap?

    Reply

    1. John

      Hi Karen. Obviously it’s hard to tell from your description your exact situation. But in general, the idea is that the hole is shut by default, and breathing in forces it shut, so that only filtered air makes its way in. Then when you exhale, you force that small hole open, and air escapes. Whilst you’re exhaling, the pressure of the air being ejected would prevent air from coming in to the respirator unfiltered.

      Not the best description ever 😅 but hopefully that makes sense. If your respirator is doing something *other* than that… it’s worth more inspection.

      Reply

  58. Avatar

    Thanks for this splendid article. I am an anesthesiologist. We have a shortage of masks. I am not sure of the masks I have in hand if their fake or not. I have been washing and drying my only 3 masks supposedly N95 every day after my work shift ends for 6 weeks. WE have no other masks in the hospital except surgical masks for regular use in the operating room. As you have noted above that we do not have a comprehensive study on covid19 regarding filtering capacities of the masks mentioned above, what you recommend to do. The infection is rising fast. I would appreciate any comments.

    Reply

    1. John

      Hi Fery, thanks for your message. That sounds like a really tough situation. I really think this is a question for an expert (which I am not) – and thus I’ll leave this comment up in the hope that someone can chime in with some better ideas. Working on the basis that re-supply of respirators is not happening any time soon (which of course would be ideal).

      Something I’ve heard about people doing is wearing surgical masks over the top of a fit tested respirator. Assuming of course the surgical masks are ones that allow for enough length in the strap to do that. The fixed over ear ones may be too short, but the tie around the head ones may be ok.

      One could presume the “benefit” would be that it will increase the filtering capacity, and reduce the amount of viruses that end up on the respirator at the end of the day. This would hopefully mitigate some of the reduction in filtering capacity that regular washing of the respirator may lead to.

      I must caveat by saying that I have not seen any evidence around this approach, so take it with a grain of salt.

      This is a shot in the dark, but there might be some readers who have sufficient numbers of respirators and can send you some. If you leave up some way for them to make contact, then it at least leaves that door open.

      Reply

      1. Avatar

        Hi, John. Thanks a lot, for your reply. I will take your advice and try the surgical masks inside and outside the respirator. It was very kind of you considering that some readers may send some extra respirators. But I think it will be not feasible under the present worldwide corona crises which have led many countries to impose heavy restrictions on exporting these gadgets. I will look forward to hearing more information.

        Reply

        1. Avatar

          Hi Fery, you can find N95 masks (+ their equivalents) & surgical masks on Aliexpress, a subsidiary of Alibaba. Prices are normal. Shipped from China.

          Reply

  59. Avatar

    National Nurses United are recommending Powered Air Purifying Respirators when there is risk of transmission via respiratory droplets or respiratory aerosols. There is a “Download the PPE Report” link on this page: https://www.nationalnursesunited.org/covid-19

    Reply

    1. John

      Thanks for sharing that Julie.

      Reply

  60. Avatar
    Marco Baratella March 8, 2020 at 6:30 pm

    ITALY – see the Covid-19 page on “PROTEZIONE CIVILE” Page

    websitehttp://opendatadpc.maps.arcgis.com/apps/opsdashboard/index.html#/b0c68bce2cce478eaac82fe38d4138b1

    Reply

  61. Avatar

    Why i cant delete comment

    Reply

    1. John

      Please refer to the section that addresses this, which is “How big is COVID-19, and can respirators filter it?”

      It already explains this.

      In essence, 0.3 microns is the hardest particle size to filter, which is why specifications focus on this. Below this size particles exhibit “brownian motion” which actually makes them easier to capture (paradoxically?).

      But see the 3M study (in the above section) that found all 6 N95 respirators they tested had 94% or higher efficacy at particle sizes around 0.1 microns – the size of a coronavirus.

      Reply

  62. Avatar

    Very interesting and well done article. Thank you

    I have a question: healthcare professional, who is less than one meter away from the person suspected of COVID 19.
    Must perform a maneuver that can generate coughing and sneezing, and therefore aerosol.
    I believe that the most suitable safety device is FFP3. What do you think about it? Thanks again

    Reply

    1. John

      Hi Cristina.

      If you can speak to specialists in your field regarding this subject, that would be ideal. There may be a whole host of factors specific to your situation that need addressing in order to ensure you are safely protected. Including guidance on “fit testing” respirators and then how to handle and dispose of them once used and potentially contaminated.

      I don’t want to get accused of giving out medical advice online, so if I just narrow the question down to “what is the highest specification of respirator you can buy in the EU” – then yes, FFP3 is the highest “official” specification. Then within the group of respirators rated at FFP3, all will filter at least 99.95% of particles as small as 0.3 microns.

      After that it becomes a choice between fully disposable vs half mask vs full mask. And then a choice between different brands.

      Fully disposable or half face are probably the least intrusive, with full face respirators being quite involved to put on and wear.

      To my knowledge 3M are one of the most reputable and reliable brands out there, so that may be ideal. They also (I believe) have some customer support available to answer product specific questions. I’m not sure where you are based, but this is the link for the UK. A quick google will bring up the relevant link for other locations.

      All the best with this.

      Reply

    2. Avatar

      Hi Christina. You should follow your guidance from you local IPC team. If you are in a developed country there will be extensive guidance on the intranet at your trust/hospital etc as well.

      There are a few concerns. Many people have other diseases that are not Coronavirus. Many of them can be transmitted also. Measles has a basic reproduction number of 12 to 18 for example. Diptheria also has a very high R0. Assuming you are dealing with just Coronavirus could be a deadly mistake. You should undertake best practice in line with your relevant local guidance. If you are in a developed country then you should take the normal precautions you would with an unidentified infectious disease. Not just masks of course but all the appropriate PPE.
      Of course it will depend on availability of equipment. More so in a developing country.

      Another issue with those working in the developed world. You may not be legally covered if you diverge from evidence based guidelines and best practice. In the UK you would not be covered by vicarious liability if you diverged from your trust/health board guidance and the established best practice. You would be personally legally, financially and professionally responsible for anything that happened when you ceased to follow guidance or evidence based practice.

      Reply

  63. Avatar

    https://habr.com/ru/post/487176/
    The Russians have collected information on protection methods, including reloading masks if there is no opportunity to take new ones. You may find something useful for your article, as English-speaking readers will never go to a Russian site.

    Reply

    1. John

      Thanks Dmitry, appreciate that. Once I’ve had a look I’ll get back to you.

      Reply

  64. Avatar

    N95 vs FFP3 & FFP2:
    Filter Capacity (removes x% of of all particles that are 0.3 microns in diameter or larger).
    0.3 microns??
    COVID-19 = 0.06 microns.

    Reply

    1. John

      Hi Orlando. Yes, that’s correct. The specifications are based on filtering down to 0.3 microns. That doesn’t however mean that is the limit to their capability.

      If you see the section below that titled: “How big is COVID-19, and can respirators filter it?”

      I look there at further research which suggests even an FFP1 rated respirator can filter down to 0.007 microns with relatively high efficacy. Jump to that section for further details and links.

      Reply

  65. Avatar

    I’m an occupational safety professional with 25 years experience in workplace safety. Never found this explained better. Thank you. 5* answer!

    Reply

    1. John

      Thanks Richard! Let me know if any bits can be improved.

      Reply

      1. Avatar

        The only thing I’ve been trying to find out is (given the current shortage of respirators) whether there is an effective way of sterilising a disposable respirator that is not heavily soiled with dirt but might be contaminated with biologically active substances (ie viruses). I’ve thought about UV sterilisation but can’t find any research. Have you come across anything? It’s not somethign I’ve ever had to consider before. Washing is clearly not an option because who knows what it will do to the filter medium but UV seems to me to be a possibility. I’ve got a couple of weeks’ supply for some healthcare workers but after that…..!

        Reply

  66. Avatar

    Hi John, this article is really helpful. For the UK, what are the CE numbers that I should look for on masks for something of FFP2 / FFP3 standard?

    Reply

    1. John

      The main one to look out for in regular disposable respirators is EN 149:2001. But for a more exhaustive list of the EN standards in relation to masks, see this 3M PDF, which is comprehensive.

      Reply

  67. Avatar

    Thanks or the great article.

    it is not clear enough if the reusable Respirators are useful. everywhere I read about them is mentioned only regarding the disposable ones.

    another thing is regarding people that have a beard. I understand that it will not be useful for bearded men and they will not be protected. what about reusable full face Respirators? I still haven’t found a suitable mask for bearded men.

    what to do regarding children?? the online info is not clear enough.

    Reply

    1. John

      Hi Benji. Unsure what you’re referring to when you say “re-usable respirators”. If you mean the half face or full face versions, these still have filters that need to be disposed of and then replaced.

      With regards to the beard, it may be ok, it will depend how big it is. The best way to check is to put a respirator on and do a “fit test” to check if air is leaking in.

      If disposable respirators are no good, then full face respirators may be your next best option.

      With regards to children, the data is suggesting that they are the least susceptible demographic to Covid-19. The recent WHO report found that just 2.4% of the 50,000 confirmed cases were for under 18s. That’s the good news. The bad news is that they may still be able to carry and transmit the disease (more research needed).

      Reply

  68. Avatar

    Thank you for this good and detailed article! 5/5 from UK.

    Reply

  69. Avatar

    Hi John,
    Given the possible shortage of P3/N95 respirators is it possible to extend the life of the filter cartridge by spraying the mask and cartridge lightly with an aerosol disinfectant such as Dettol All in One which is specified to kill superbugs such as MRSA etc and then letting it dry overnight

    Reply

    1. John

      Hi Rick. It’s a really important question as you say. We can anticipate shortages of respirators, so what can we do to increase the life cycle of them?

      With regards to the Dettol All in One, I honestly don’t know the answer, and wouldn’t want to say one way or the other without more info.

      I see the ingredients are listed as:
      – 57.81g ethanol, 0.09g Alkyl Dimethyl Benzyl, Ammonium, Saccharinate

      But I don’t know enough about material/chemical science to know if any of those could degrade the efficacy of the materials used for filtering. If they did… we’d then be shooting ourselves in the foot, because we’d be trusting a respirator that no longer operates at its maximum capacity.

      If I can advance this conversation any further I’ll post an update.

      Reply

      1. Avatar

        Hi John, very good point about degrading the filtering medium. I propose to use a GVS Eclipse P3 respirator so will endeavour to contact the manufacturer to see if they will comment on the suitability as obviously the mask itself will need regular disinfection. I will post any information I get.
        Many thanks

        Reply

        1. John

          Thanks Rick, that would be great!

          Reply

        2. Avatar

          I’m guessing that no manufacturer would commit themselves. Too much room for law-suits – but it would be interesting to know!

          Reply

          1. John

            I saw this 2015 paper that used Ultraviolet Germicidal Irradiation (UVGI) N95 respirators. Quote:

            • “UVGI uses ultraviolet light to inactivate microorganisms, primarily by cross-linking thymidine nucleotides in DNA and uracil nucleotides in RNA, which blocks replication. UVGI systems are relatively quick and easy to use, and do not leave chemical residues or risk exposing workers to toxic chemicals. In the lab, UVGI has been successfully used to decontaminate N95 respirators exposed to the bacteriophage MS2 and influenza virus.”

            But I don’t know how widespread these are. Then it’s a case of learning how to calibrate to maximize RNA denaturing, without reducing the efficacy of the respirator too much.

            This later 2018 paper, on the same subject concludes by saying:

            • “These data suggest that FFR decontamination and reuse using UVGI can be effective. Implementation of a UVGI method will require careful consideration of FFR model, material type, and design.”

  70. Avatar

    Hey John really helpful article love it great. I wanted to ask though I am trying to get my hands on the P100 or the N100 bit I can’t find them anywhere now I am ordering it from ebay for 3x the normal cost. I wanted to in very simoke terms does the P100 or N100 block the coronavirus air droplets? And last thing could anyone here please help me get the N100 or P100? I’ll pay extra I live in Pakistan so I’ll pay for the post/delivery service aswell. Thank you

    Reply

    1. John

      Hi Fahim. Yes, if you can get hold of P100 or N100 (comparable to FFP3), that’s about the highest filtration standard you can buy, and from the studies I’ve looked at, this will filter particles the size of the coronavirus with high efficiency.

      Reply

  71. Avatar

    Hi John! Thank you for such an informative article. Would you advise people to use the FFP1 respirator over 3 ply masks and would you know if FFP1 is at all effective against the Covid-19 virus?

    Thank you!

    Reply

    1. John

      Hi, yes, FFP1 rated respirators have greater filter capability to 3 ply masks (also called surgical masks).

      With regards to whether FFP1 is effective against Covid-19. This article cites sources for the 3M 8812 respirator (FFP1 rated) being able to filter 96.6% of particles 0.007 microns or larger. With Covid-19 being between 0.06 and 0.14 microns in size (larger than the 0.007 microns it can filter down to). That suggests that other FFP1 rated masks should achieve similar results. Ideally go for a reputable brand such as 3M where possible.

      Reply

      1. Avatar

        Thank you so much for the detailed reply!! 😊 Will definitely follow your advice.

        Reply

  72. Avatar

    So from I understand the ffp3 has better protection than the ffp2 from the flu virus. You mention the ff2 block colds and coughs does the ffp3 do the same thing

    Reply

    1. John

      Both FFP2 and FFP3 respirators have the capability to filter viruses, but FFP3 respirators should filter a higher % of them.

      Reply

  73. Avatar

    Hi John
    I have the Honeywell “Optifit Twin Full Face Respirator” with the ABEK1/P3 cartridges.
    Your thoughts on it and how long would you recommend using the cartridges before they need replacement?

    Reply

    1. John

      Hi Lukas. Presumably an ideal scenario the filters are replaced daily, especially if in known contact with sick people. In practice, however, not everyone will have access to this number of respirators/filters. We’ve seen that already in China.

      So then presumably there exists a balance between the ideal (regular replacement), and the opposite (not using a mask/respirator).

      Whilst I won’t pretend to know what the correct balance is, I can try to add a bit to the conversation.

      There are at least 3 risks with mask/respirator re-use:

      1. Risk of contamination from touching the outside, which houses captured particles (including viruses).
      2. Once used, risk of contamination from the product whilst its being stored. For example, virus particles being lifted off the mask into the air.
      3. Risk that the efficacy of the product decreases over time with usage.

      In response to these:

      1. When putting on and taking off the mask, one should touch the front as little as possible, and wash hands carefully after.
      2. When storing the mask, one could place it in a sealed container, to minimize circulation of any virus particles.
      3. In terms of the rate of efficiency decline, this small-scale study found that after 11 days of use whilst biking around Beijing, a 3M 9332 mask (FFP3) had gone from 99.7% to 98.3% of particles blocked in the 0.01 to 1 micron size range. Whilst this is hard to extrapolate too much from, it at least gives us a data point for the rate of function decline.

      If someone is aware of more data on this subject, it would be great to hear.

      Reply

      1. Avatar

        You can take 7 filters and use one every day. Covid-19 die by 5 day in open air. If you store the filters in the right conditions, the virus will die even faster, high temperature (maybe 60 degrees Celsius).

        Reply

  74. Avatar

    In some respirators it is mentioned FFP2S. Could you please let me know the filter capacity of this in %?

    Reply

    1. John

      Hi Kris. Masks marked as FFP2S, as long as they’re from a reputable source (such as 3M) will have been tested to filter at least 94% of particles 0.3microns or larger (FFP2 standard).

      Reply

      1. Avatar

        Thanks a lot 🙂

        Reply

  75. Avatar

    Hi John

    Is there any difference in p3 and FFp3 filter?

    Reply

    1. John

      Hi, yes, P3 and FFP3 are the same. P3 is just an abbreviation of FFP3.

      Reply

  76. Avatar

    Hi John, would microwaving a disposable mask help to decontaminate it and make usable for longer?

    Reply

    1. John

      Hi Simon, I would steer clear of that approach unless you can find evidence for its efficacy in scientific literature. Without knowing more, I’d assume the key risk is damaging the mask/respirator such that it no longer filters air as per its specifications.

      Reply

      1. Avatar

        Metal components on respirators (nose clip) and microwave – not good idea. But thought about re-use to overcome shortages deserves consideration. Would sticking a mask in freezer overnight do the job and kill the virus? I know bacteria don’t fair too well after freezing? A method for re-use with commonly available kit would be useful.

        Reply

        1. John

          Hi Graeme. Unfortunately to my knowledge, freezing a virus may preseve it, rather than inactivate it. That’s correct though about bacteria, the freezing and then re-thawing process can kill them.

          Definitely agree we need a method of re-use for respirators.

          Reply

  77. Avatar

    0.3 micron for FFP2, but how small particles does FFP3 filter out? And how small is the coronavirus?

    Also, I’d like to add that masks should be taped to your face. The air flow will take the path of least resistance, and the gap between the mask and the skin can easily be larger than microns, even millimeters.

    Reply

    1. John

      Hi Havard, great questions. I’ve added a section to the post to cover this. Let me know if it leaves any further questions.

      Reply

  78. Avatar

    Hi John very nice article. As there is shortage of respirator around the world. Do you think we can use UV-C machine to prolong the life of the respirator ? I find this in the web for your reference: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4699414/

    Thanks

    Reply

    1. John

      Hi GP. That’s a fascinating idea, and good paper on the subject, thanks for the share. As you rightly point out, there are shortages of respirators, and safe re-use would be very valuable – especially with the continued increase in number of cases. Especially in hospitals, where healthcare professionals are going through 100s of respirators each day, and they are vitally needed.

      So the idea hinges around using Ultraviolet light to kill viruses and bacteria, which is straightforward enough. They mention that the doses of UV needed will vary based upon the pathogen being targeted. Their key concern is that the UV may degrade the respirator itself and reduce its function.

      What this suggests to me is that we need to take the most common respirators, create a simple chamber where the masks can be hung in rows, facing the UV light, and then research the minimum amount of UV needed to kill pathogens (COVID-19 included). Then calculate how many times the mask can be re-used before it begins functioning badly.

      Perhaps the masks can be tagged with barcodes, and scanned in before using the machine, at which point it could warn when masks need to be disposed (avoiding human error).

      Certainly you wouldn’t want to risk doing this “at home” until we know more about how to do it safely and effectively.

      Reply

  79. Avatar

    Very good article, thank you. 🙂

    It isn’t ideal but because of the mask shortage people have started to make their own disposable masks using a combination of kitchen paper, tissue, coffee filtre and other dry sheet to make a 3-layered barrier. Use a stapler or even a tape if you can’t sew. Include thin wire or aluminium foil to fit the mask to your contour around your nose. Hair bands/rubber bands are handy. https://www.youtube.com/results?search_query=surgical+mask+diy

    Re-use of disposable mask can be risky but in a pinch, I read a notice which said use a high setting (above 50C?) on your hairdryer to kill the virus.

    Reply

    1. John

      Hey Andy, cheers for the message. That’s pretty crazy that people would resort to DIY versions. That said, if there’s a shortage of masks, and you know you’ll be around infected people… then yeah… that’s potentially better than the alternative – which would be no mask. And they would certainly help stopping people touching their nose and mouth with their hands.

      Reply

  80. Avatar

    Hi John, simple question – will the GVS Eclipse P3 work for coronavirus? Thank you

    Reply

    1. John

      Simple answer, yes (as best the scientific community know), when worn correctly. This then needs to be coupled with other adequate preventative measures, such as keeping hands clean (and away from touching the face).

      Reply

      1. Avatar

        Thank so so so much, you have cleared the things , i was really confused in this point , and now is clear and Also i have learned many things, new information
        I have question please
        Can the corona virus resist onthe the things , i mean if someone is infected and he touched something after that i touched the same thing , is the virus still there or is already died
        I’m in china right now and they advise to wear surgical masks when get out from home ,but in case you need to go to hospital you mast wear the respirator n95 ,
        Thanks Mr John

        Reply

        1. John

          Hey. Regarding your question – “Can the corona virus resist on the the things, I mean if someone is infected and he touched something after they touched the virus, is the virus still there or is it already dead?”.

          Here’s what I understand…

          Yes, the virus can land on objects and continue to function for a period of time. So for example, if someone sneezed on something, which you soon after touch, you could end up inadvertently transferring the virus to yourself if you next touch your face (eyes, nose mouth) with that hand.

          What we don’t know is how long the virus can continue to function outside of the body. A literature review (link) published in the Journal of Hospital Infection analyzed 22 studies of related corona viruses (MERS, SARS and HCoV), and found that they can persist on objects like metal, glass or plastic for up to 9 days in duration. Which indicates that the corona virus may be able to last for a period of time too – but we’ll need further research to figure out exactly how long.

          So that is a primary reason for lots of hand washing and attention to personal hygiene.

          Let me know if that helps answer your question.

          Reply

          1. Avatar

            Thank Ms John , i understand, yes that was my question , i have another question, i find mask which written in the box that is ffp2 with CE and EN149:2001 , is this information enough to ensure that is good mask like n95 , because the shape of this mask it looks like other surgical masks , the one i find is white without valve and is made in france by the way , I’m asking this question because I’m in china , so i need to find the right mask , [email protected] this is my email or if you could give me yours i can send you the picture to confirm , thank you in advance

          2. John

            Hi Bakir. Regarding masks that are rated FFP2 (EN149:2001) with CE – but look like surgical masks…

            Even if the material of the mask has the capability to filter to FFP2 standard, my concern would be that it’s not possible to do (what seems to often be called) a “fit test” on them. Link to video demonstrating the test, which checks for air gaps (from ~2m 10s).

            That’s one of the key differences between a mask and respirator; the respirator should fit tightly enough that no air can leak in from the sides (and avoid filtration). Compared to surgical style masks that leave gaps.

            Of course, if this is all you can get access to in the way of masks, then it should be better than nothing. But otherwise, I would try to find a respirator (not mask style) with at least FFP2, or ideally FFP3 standard.

  81. Avatar

    Does FFP2 standard includes the fluid resistance requirement?

    Reply

    1. John

      Hi Jack. So if we’re referring to fluid resistance in the sense of the “surgical masks” that include fluid resistance (ASTM F1862 standard). Then none of the standards (N95/N100 or FFP2/FFP3) include that as standard, but there are masks that include it in addition. For example; 3M’s 1860 and 1870+ masks, which are specifically approved for surgical use, including the ability to resist high pressure fluid at a short distance.

      Let me know if that makes sense and helps answer your question?

      Reply

  82. Avatar

    There are FFP2 mask with EN 149 + A1:2009 Duckbill with no filter. How good are they ?

    Reply

    1. John

      Hi Saher, thanks for the message. First time I’ve seen this duckbill style. The ones I’ve seen online, from a quick search, all appear to be made of a soft material, and are essentially masks rather than respirators. Note – that doesn’t mean they are all like that… but just the ones I’ve seen so far.

      My concern with those is that *masks* don’t fully restrict the inflow of air – meaning that the air can be sucked in through the sides and doesn’t get filtered. These are generally used in medical settings, but not in settings where you have a highly transmissible virus.

      Reply

  83. Avatar

    This is the best article available on the internet when I started looking for an answer that which mask or respirator should I buy for my family in case coronavirus breaks loose in my area. I stay in New Delhi and risk factor is very low at the moment but can’t say about the future. Thankyou John for posting this.

    Reply

    1. John

      Hi Ashish, thanks for the message, glad to hear it helped! Fingers crossed things stay safe in New Delhi 🙏

      Reply

  84. Avatar

    Hi,
    For how long can the disposable respirators be used?

    Reply

    1. John

      Hi Tsa, good question. There are some CDC guidelines (link) that say:

      “Workers in other industries routinely use N95 respirators for several hours uninterrupted. Experience in these settings indicates that respirators can function within their design specifications for 8 hours of continuous or intermittent use.”

      They also make a few other things clear:

      • Respirators should be discarded when contaminated with bodily fluids
      • Respirators should be discarded following close contact with an infected person
      • Careful hand hygience should be exercised before and after touching and adjusting the respirator

      That last point is particularly key – given that the front of the mask is fitering the air; viruses and bacteria could build up on it. Thus after touching it one should wash their hands thoroughly.

      In high risk medical settings you could imagine medical professionals replacing their masks daily (at minimum). Outside of this, I could imagine people replacing their masks less regularly – in particular due to practical restraints, such as costs and supply shortages. If the mask is getting re-used for days, it makes practicing good hand hygiene around it paramount.

      Citing another source, a researcher discussed on Quora (link) how he used new 3M 9332 respirator for 11 days, 3x day in Beijing, and found that by the end, it was blocking 98.3% of particles, compared to originally blocking 99.7%. Which gives an idea of how quickly, or not, respirator function detereorates.

      Reply

  85. Avatar

    Hi there

    Does this article apply to the 8810 ffp2 mask as well? How does that compare to the n95?

    Thank you for a very informative article

    Reply

    1. John

      Hi Susie, yes the 3M 8810 FFP2 respirator will be equivalent to the US N95 standard.

      Essentially each jurisdiction has its own set of standards, and 3M conform to them. So they’ll qualify masks as N95/N100 in USA and FFP2/FFP3 in Europe.

      For reference here’s a datasheet on the US version of the 8810, which mentions its N95 approval.

      Reply

      1. Avatar

        Thanks John!

        Reply

  86. Avatar

    n95 1860 equal to which type of FFP2?

    Reply

    1. John

      Hi Yiwei, the 3M 1860 would be equivalent to FFP2 (non surgically approved).

      Reply

  87. Avatar

    There is a huge gap between the demands and supplies of respirators in Wuhan.

    Data on Feb 06: in Wuhan the *daily* demands on N95 respirators: 119,000 pieces, Gap: 56,800 pieces;
    They also lack of protective clothes, goggles, etc…

    Nurses even have to wear plastic bags to protect themselves because of lacking protective clothes…

    AFAIK, over 1,100 doctors and nurses had been diagnosed or suspected of infection just in Wuhan by Feb 06 based on a slide from CDC (China Centers for Disease Control and Prevention)

    Reply

    1. John

      Hi Yina, thanks for the share. Yes, can imagine the strain on protective equipment (PE) resources must be huge.

      There was an encouraging blog post on 3M’s site saying that they have ramped up production of protective equipment in response to the coronavirus (as you’d imagine).
      Apparently the majority of what they make locally gets sold locally – so product made in China is sold in China. They haven’t increased their prices in-line with the demand, but that they can’t control what resellers do with the price.
      Link: https://news.3m.com/blog/3m-stories/3m-responds-2019-novel-coronavirus

      Huge respect and gratefulness to the health professionals on the front line, risking their health 🙏

      Reply

  88. Avatar

    Good stuff. It will be even better if you can cover also water repellent or splash resistant nature of some N95 (or comparable standard) respirators for medical use like 3M 1860. There is a debate in HK whether the 3M N95 respirators for industrial use like 8210 are not good against virus laden droplets or aerosol since they are not water repellent. Thx.

    Reply

    1. John

      Thanks CK.

      Have had a look into this, and have added some details here.
      My layman’s interpretation of the difference between 8210 (non-medical) and 1860 (medical use) is that they are both adequate for most day to day situations.

      Where the 1860 would excel, is if sprayed with high pressure liquid from a close distance (tested at 30cm), which it can keep out. You can anticipate this scenario might happen during surgery (e.g. punctured artery).

      Reply

  89. Avatar

    Wonderful article! & thanks !

    Reply

  90. Avatar

    Thank you very much for this excellent Information, John.

    Reply

  91. Avatar

    Thank you very much! 🙏🙏🙏

    Reply

    1. John

      Thanks for the message, glad the post helped.
      Let me know if there are any questions I didn’t touch on (especially HK related). Thanks.

      Reply

  92. Avatar

    Any recommendations for toddlers in us?

    Reply

    1. John

      Hi Laura, whilst there are models made for small children, it looks like the majority of stock is sold out. Will leave this comment up in case anyone has ideas for where to source in USA.

      Reply

    2. John

      Hi Laura, I know it’s a bit late (but hopefully better late than never?) – I’ve added a post on the supplements Rhonda is giving to her toddler here. In essence she’s opting for a multivitamin, fish oil, vitamin D and vitamin C. Generally sticking with brands she trusts such as Pure Encapsulations, and aiming for low to zero sugar. The rest of the details are in the post. Hope that helps!

      Reply