Are FFP2 (N95) masks the best choice for reducing COVID-19 transmission - What does the science say?
Masks, masks, masks: A surgical mask, an FFP2 (N95) mask, and a community mask
A quick note before we begin: The scientific studies and information I reference here is what is available at the time of publication of this article - as the NCBI says, "COVID-19 is an emerging, rapidly evolving situation" - so, it is possible that things will change in the future. Also, this is not intended to be an all-encompassing review of the scientific literature, but instead a means to point you in the direction of information that might be useful to you in making decisions about your own personal protective equipment in your own individual circumstances.
I am a scientist by training - specifically in cancer cell biology. I know a lot about biochemistry, immunology and cell signalling. I am also interested in reading the latest scientific literature. See here if you’re interested in learning more about my scientific career and my pivot away from the lab bench.
I thought it might be nice to use some of this knowledge and try to cover and simplify some scientific concepts, information, and research for those of you out there that are not scientists (or those scientists that may not have the time, energy, or desire to trawl through the scientific literature on these topics).
Today we're discussing the use of FFP2 (N95) masks
A FFP2 (N95) mask
Here we’re tackling the question of whether FFP2 (N95) masks are really better than the surgical and community masks (commonly used to date) in reducing COVID-19 transmission. We'll cover some basic background and then take a dive into the scientific literature to see what the research says.
Despite the fact that the World Health Organisation (WHO) maintains that surgical masks (ie the blue or green ones most commonly made of 3-ply propylene) and community masks (made of fabric) are sufficient to reduce COVID-19 transmission in the community (as well as in most medical settings), both Germany and Austria have recently mandated the used of FFP2 masks for the general public (specifically in situations where people are in close confines: such as on public transport, in shops, doctor's surgeries and in (some) workplaces.
Bavarian Minister President Markus Söder has stated in an attempt to explain the reasoning behind this new requirement: "If the virus becomes more dangerous, the mask has to get better".
On the opposite end of the spectrum, the European Centre for Disease Control and Prevention (ECDC) "does not support the wearing of FFP2 masks in the community, according to the evidence they have."
So, why are Germany and Austria enforcing the use of FFP2 masks and are they really "better" than surgical or community masks?
Let's start with some basics
Note: I call them "basics" but there has been much debate over how COVID-19 is transmitted. Airborne transmission was originally refuted, but now there is increasing evidence that it is also a transmission route, especially under specific circumstances.
COVID-19 (caused by the virus SARS-CoV-2) is thought to be transmitted in a number of ways
Droplet transmission:
When an infected person exhales, speaks, sings, coughs, sneezes, spits and so on, they produce large droplets that most likely also contain infective virus.
These droplets are normally large - and are often visible.
They fall out of the air rapidly and close to the source (ie within a couple of metres, which is why maintaining distance from infected people is one way of reducing the odds of coming into contact with the virus and getting infected).
This is thought to be the most common route of transmission.
Aerosol or Airborne transmission:
This is transmission by small droplets and particles containing infective virus.
These small droplets and particles (aerosols) can remain suspended in the air for a much longer time (minutes to hours) than large droplets and can cover greater distances in airstreams.
This type of transmission can occur in some specific circumstances, such as:
In enclosed spaces (like a subway carriage)
With prolonged exposure to particles (ie staying near an infected person for long periods of time)
Inadequate ventilation (like when the windows are closed)
In some cases of aerosol or airborne transmission, people can become infected without ever coming into contact with the originally infected person: their infection occurring after the infected person has left the space.
Direct or contact transmission:
This is where someone comes into direct contact with:
An infected person (eg touching them and their saliva)
Or touches an infected surface "formite transmission" (this appears now to be a rare source of infection - even though the virus can remain living on surfaces for days to weeks, scientists have found it difficult to grow live virus from these surfaces).
When will you get infected?
When a high enough concentration of virus comes into contact with your mucous membranes (such as those lining the nose, mouth and eyes).
What is the purpose of a mask?
To prevent virus from an infected person reaching the respiratory tract (or eyes) of an uninfected person
How? By providing a barrier (and possible also, a filter). Depending on many factors (the type of mask, the material, the fit, whether it is being worn correctly - more on that later) this will, to a certain extent:
Limit the amount of droplets or aerosols released by you from coming into contact with others (the mask can "catch" these)
And, also limit the amount released from others that come into contact with you.
What are FFP2 masks? (some nomenclature)
They are essentially similar to N95, KN95, and P2 masks (providing a similar level of protection)
FFP2 stands for: Filtering Face piece Particles protection level 2
Made of many layers of paper and fabric
They protect others from the wearer, but also protect the wearer from inhalation of airborne particles
They can filter at least 94% of airborne particles
Are FFP2 masks better than surgical or community masks in reducing transmission of COVID-19 - What does the science say?
Same level of protection against influenza
Two groups of scientists that performed analyses of existing studies have suggested that N95 (FFP2) masks and surgical masks provide the same level of protection against influenza virus, and potentially even coronaviruses.
But what about COVID-19?
The case for FFP2 mask use over surgical mask use
A surgical or medical mask
Another group demonstrated that N95 (FFP2) masks might be more effective in preventing COVID19 transmission than surgical masks. But even they only suggest them for medical practitioners, and not the general public.
Some scientists have developed a tool to directly compare droplet transmission from a speaker wearing 14 different types of masks:
In this study, the N95 mask (equivalent to an FFP2) worked the best (lowest number of droplets detected) but (and this must be noted) this was a "professionally fit-tested N95 mask" (more on fit a little further).
They also found that the non-valved N95 mask was better at preventing droplet transmission than the valved mask.
But, the surgical mask (with 3 layers) came very close behind - suggesting that they could be protective enough in community settings.
A case for surgical masks over FFP2 masks
Another group of scientists directly compared surgical masks versus FFP2 masks to determine in which case less droplets would pass through.
They use a nebulizer to spray some fluorescently-labelled (dyed) water to determine in which case more droplets got through the mask to the dummy head.
Interestingly, here, surgical masks provided even better protection, arguing against the specific use of FFP2 masks.
Other scientists argue that "the current knowledge provides no scientific evidence from head-to-head studies in favour of using FFP2 instead of a surgical mask outside the so-called AGPs (aerosol generating procedures, in a healthcare setting)".
Fit is key
I noticed in my reading that the concept of a properly fitting mask came up again and again. I think this is key: masks (any type) are only maximally effective if they are worn correctly. This is especially important in the case of FFP2 masks - their safety rating, and effectiveness is only applicable when worn properly.
What is the correct fit for an FFP2 mask?
Scientists have suggested that there needs to be a tight fit around the users face, this can even be uncomfortable. Others have suggested that there needs to even be a "tight facial seal".
Achieving this "proper seal" may even require facial hair removal.
You should also ensure "that the upper nose wire is moulded symmetrically over the nasal bridge using the fingers of both hands to create a tight seal" - see here for more details.
Why is a tight fit important?
"Airborne protection is decreased in the presence of a leak as unfiltered air will be drawn inside the mask. Correct respirator fit appears far more important for airborne protection than the filtration capacity of the material", say scientists Regli and colleagues.
Another way of putting it (by Jonas Schmidt-Chanasit, a German virologist and Professor of Arbovirology at the University of Hamburg): “In most cases FFP2 masks will be ineffective if they aren’t professionally fitted: people will end up breathing through the gap between mask and face rather than through the designated filter.”
So, it doesn't matter how much your mask can in theory reduce transmission of droplets, if it doesn't fit correctly you are not protected and you are not protecting those around you.
How can you tell if your FFP2 mask is the correct fit?
An easy way to tell is if “the [FFP2] mask collapses slightly when you inhale."
Check out this video for a nice detailed explanation of how you can check you're wearing it properly.
What does the science say? If properly fitted, FFP2 masks can be quite effective at reducing transmission of COVID-19
I think the jury is still out on whether surgical masks are just as good (especially in community settings), but it seems that if you manage to wear it correctly, an FFP2 mask might be a good choice.
But what are the downsides of FFP2 use in the community?
Risk of (untrained) general public wearing them incorrectly
France's Health Advisory Council has argued that "the possibility of them being worn incorrectly may actually increase transmission risks".
As stated above, if people don’t wear them correctly, they could be breathing unfiltered air, dramatically reducing their effectiveness. People could believe that they are appropriately protected and may not follow other rules such as keeping distance or ventilating enclosed spaces.
Expense
FFP2 masks are intended to be single-use, but they can be somewhat expensive (especially considering that you would need to keep buying them). Surgical masks are relatively cheaper, and community masks can be washed and reused.
The substantial cost involved could lead people to re-wear them beyond their capacity.
Or to "process" them incorrectly: Scientists at the Münster School of Health suggest a protocol to disinfect FFP2 masks in order to re-wear them: "First let the mask air-dry for a day. Then preheat your oven to 80 degrees Celsius (top and bottom heating), place the FFP2 mask on baking paper and then place it in the oven for 60 minutes. The mask should only be reprocessed five times in this way and then disposed of in household waste". They've demonstrated that this protocol will kill most virus, but to me it sounds a little involved. Hands up if you're going to do that? Anyone?
Then there are other health issues that can be induced by wearing FFP2 masks:
Scientists reported a patient who developed an orbital-conjunctival-eyelid hemorrhage-hematoma due to incorrectly wearing an FFP2 mask.
Others say that "when using an FFP2 mask, breathing is more difficult due to the built-in filter. The additional strain on the respiratory muscles is comparable to breathing through a straw and can result in shortness of breath - so you should think carefully about when and for how long you want to wear the mask."
Which brings up another issue: occupational health and safety rules in Germany stipulate that FFP2 masks should only be worn for 75 minutes at a time but there are often situations (such as on public transport) where masks must be worn (without break) for longer times than that.
So, should you wear an FFP2 (if it's not mandatory where you live)?
An example of a community mask made of cotton
I'm not here to tell you what you should or shouldn't do, merely to outline some of the scientific literature to get you thinking about what might be the best option in your circumstances.
In any case, you should wear some type of mask regardless (when you're around others outside your household, obviously).
If you choose to wear an FFP2 mask:
Wear it correctly (do some of the little tests outlined above to check)
If you can't get your FFP2 mask to fit correctly, then you may have to trial out some different brands or types. For instance, I've noticed that the ear strap can be variable - I had one type that pulled on my ears so much it made them red and sore, but others I've bought don't cause these problems.
Be wary of which brand you buy and make sure it conforms to standards. One study compared various FFP2 masks and found that 5 out of 15 didn't meet FFP2 standards. Check here if you are concerned about FFP2 masks you've bought.
Re-use? They are intended to be single use. But, if you're going to re-wear them, follow the instructions I outlined above, and don't wash them (moisture reduces their effectiveness).
Don’t use one with a valve! This will allow an unfiltered outlet for your breath, so you won’t be protecting those around you.
Try not to wear them for longer than 75 minutes at a time.
If you choose to wear a surgical or community mask:
Make sure you're wearing it properly: see here for a video from the WHO.
Consider mask material: The small study I referenced above (the one that showed FFP2 masks to fare the best) demonstrated that, beyond surgical masks, cotton-propylene-cotton (3 ply) masks and two layer polypropylene layer masks performed the next best.
Beware of neck gaiters and bandanas: This same study also demonstrated that neck gaiters fared the worst - and may not even be better than wearing nothing (in fact they appeared to disperse the larger droplets into smaller droplets that can remain suspended in the air for longer). After neck gaiters, bandanas were the next worst, and appeared to provide limited extra value compared to wearing nothing at all.
Wash your re-usable masks regularly.
In either case:
I shouldn't even have to say this here, but make sure your mask covers you nose as well as you mouth! I see at least a few people everyday with their noses exposed!
Consider hand hygiene before putting on and taking off your mask.
Don't touch your eyes (this is also a portal for COVID-19 infection) and consider wearing eye protection.
Avoid or limit being in confined spaces without masks.
Keep your distance.
Okay, this article kind of ballooned out - which I think points to the fact that this is a complex issue. As I said at the beginning, COVID-19 is a new and evolving situation: there is still so much we don't know about COVID-19, but well-crafted and executed scientific studies will be pivotal in deepening out understanding and informing policy decisions.
Take home message
Wear a mask and wear it properly. There is still debate over whether FFP2 masks are useful or should be required in community settings, but, regardless of whichever mask you are wearing: better fit = more effective in limiting the spread of COVID-19.
Further reading:
Nature News provides detailed articles about a lot of different aspects of the pandemic (as well as a multitude of other scientific topics) - they summarise the latest scientific findings very nicely. See here.
I hope you've enjoyed this article. What are your thoughts on this issue? What type of mask do you wear and why? Leave your comments below!
An extra favour: if you've read this, then please let me know what you think. If you don't feel comfortable commenting publicly, you can reach out to me through my contact page, or message me over on Instagram. All feedback is welcome and will really help me to decide in which direction to concentrate my efforts on this blog.
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