First posted 23/2/2022
MBBS, MAppFin, GradCertPubHlth, FRACGP, FACEM
Dual trained Specialist Emergency Physician & General Practitioner
Clinical Senior Lecturer, University of Western Australia
As COVID-19 spreads across Australia more and more people are considering buying N95/P2 masks (hereafter referred to as P2 masks) to wear in public places.
Is it really necessary?
While much of COVID-19 transmission occurs by “droplet spread” which can be reduced through the wearing of standard masks (i.e. surgical masks and probably to some extent cloth masks) together with frequent hand hygiene and social distancing, a significant amount of COVID-19 infections are spread via the airborne route which can bypass standard masks. The P2 mask (which goes by many names – see terminology) helps reduce COVID-19 infection via the airborne route.
Additionally, conceptually it is useful to note that the purpose of a standard mask is primarily to help protect other people from the mask wearer by reducing their transmission of the virus by the droplet spread route. This is especially useful when the mask wearer may be infectious but asymptomatic (or minimally symptomatic) and consequently is not yet diagnosed and isolating. Standard masks unfortunately aren’t thought to do a great job of protecting the mask wearer themselves from COVID-19 infection. By contrast, the P2 mask, in addition to protecting other people, can help protect the mask wearer as well.
If you are living in an Australian state with rampant COVID-19, it is probable that you are going to be infected with COVID-19 in the not too distant future, either as a symptomatic or asymptomatic infection. The dominant omicron variant is highly transmissible and it is expected that the most people will eventually contract COVID-19 as a result, either due to omicron or a future variant. The actual number of infected Australians is unknown but is it expected to be many times higher than reported figures for several reasons including that the majority of omicron cases are asymptomatic or mild and remain untested and therefore not officially confirmed.
So the use of an P2 mask may only delay your COVID-19 infection, not prevent it. This is particularly the case because:
The very best thing you can do to reduce your chance of symptomatic infection and severe disease is to get double vaccinated and then get a booster. The booster has been shown to be important in maintaining immunity and providing reasonable protection against newer variants such as omicron.
At the time of writing, supply of P2 masks (also known as P2 respirators) to the general public is extremely limited in Australia and they remain relatively expensive. Additionally it is difficult to understand the different competing terms used to describe P2 masks and easy to be lured into scams selling fake masks that don’t meet the standards.
There are various terms used by different countries to authenticate that a mask meets the standard where approximately 95% of airborne particles are filtered out. P2 (Australian) and N95 (American) are the most common and essentially equivalent.
These standards are also considered essentially equivalent by the Australian Government (Infection Control Expert Group).
While these alternative classifications are equivalent, there is potentially increased risk of being sold a “fake product” if you buy the alternative mask classifications, particularly from a non-trusted or dubious credibility vendor. Indeed the US CDC found 60% of KN95 masks being sold in the US did not meet standards.
The CDC has provided tips for spotting fake masks here and more tips here – some useful generic tips but some are only useful for spotting a fake mask labelled N95.
Additionally for a proper tight fit, P2 masks usually have 2 tension headbands that fit over the lower and upper parts of the head. Masks claiming equivalency that only have single ear loops on each side are much less likely to meet the standard of effectiveness.
Valved masks: P2 and equivalent masks are also available in a variety that contain an expiratory valve. These are designed to provide protection for the mask wearer from inhaling aerosols but when the wearer exhales their breath passes through the valve “unfiltered” into the surroundings which means people in the vicinity of an infected mask wearer are not well protected from them. Consequently these masks are intended for industrial use when the wearer is requiring protection from aerosolised tiny particles (like dust) e.g. in building worksites. They are not designed or recommended for use in infection control as they protect the wearer from their surroundings but don’t properly protect other people from the wearer. Compared to an un-valved P2, they are thus a clearly inferior product for this purpose. Compared to a standard mask though, they still offer superior protection of the wearer but probably also offer inferior protection of other people from the wearer, but it is difficult to know exactly how inferior it is.
It’s important that you “don” (put on) and “doff” (take off) a P2 mask carefully to maximise the chance it will be effective and minimise the risk of contamination of yourself, clothing or surroundings with infectious particles trapped on the outer layer of the mask. It’s also important to use hand hygiene before and after donning or doffing the mask. It’s crucial that you manually fit the mask to your face including by moulding the nosepiece over your nose to obtain a good seal.
Once donned, you need to check that the mask is working properly. A reasonable way to check this is to perform a “fit check”. If you fail the fit check, readjust the mask fit to your face better but if you continue to fail the fit check afterwards, the mask is not providing you the certified 95% airborne protection and you may need to find a different P2 mask to try.
This video demonstrates the process of donning and fit checking a P2 mask.
Aside from this quick and easy “fit check”, you can in theory undergo more accurate formal “fit testing” but due to cost and availability, this is generally only provided in key workplace settings such as healthcare, though if determined one may be able to source and pay for privately. However you should fit test a few masks simultaneously and ensure you can access a good supply of the mask(s) that you pass the fit test on, or you might have wasted your money being tested.
It is generally difficult to obtain a good seal with significant facial hair so a clean shave is recommended prior to use of P2 masks.
P2 masks are usually single use disposable masks. Given the cost and difficulties with supply, many people will be tempted to reuse these masks. This is generally not recommended as the effectiveness of the masks can be degraded by usage and decontamination procedures. Also users can easily contaminate themselves with pathogens that exist on the outside of the mask if they are not trained in proper donning (putting on) and doffing (taking off) techniques combined with safe mask storage. Note that healthcare providers trained in doffing can easily make errors in the process so the untrained are even more likely to do so and contaminate themselves.
As the supply of P2 masks was very limited in healthcare settings in the early stages of the pandemic, healthcare staff in the US were forced to reuse masks and the CDC provided advice to optimise a suboptimal situation. On this page, under the heading “a limited reuse strategy to reduce the risk of self-contamination” the CDC advised after using a P2 mask, to store it in a breathable paper bag for a minimum of 5 days before reuse (as most airborne pathogens including COVID-19 will die off during this time). They recommended a maximum of 5 separate uses of a single mask stored in this way. So 5 uses, separated by 5 days!
There are several decontamination procedures that might allow one to reuse a mask within the 5 day period but most of the techniques are both impractical and untested outside of healthcare/industrial facilities and some techniques can damage either the mask filtration or the bands that secure the mask to the head, which compromise effectiveness of the mask.
The decision to wear P2 masks routinely in public is closely related to what extent an individual wishes to delay COVID-19 infection in themselves.
It is important that members of society take the measures recommended by their governments and medical authorities to minimise the spread of COVID-19 to other people. The government also may choose to enact strategies to prevent everyone “catching COVID-19 all at once” and instead spread out the wave of infections so as not to overwhelm health systems or disable essential industry workforces.
The question then is, should an individual take extraordinary measures to delay COVID-19 infection – by subjecting themselves to more extreme social isolation, wearing a P2 mask routinely whenever in public and even wearing a P2 mask when visited/visiting in private homes – hereafter referred to as a “delay infection strategy”.
Assuming:
… then there may not be much to be gained by pursuing a “delay infection” strategy by taking such extraordinary measures. In fact there are reasons why delaying infection may not be in your best interests:
With the important caveat that future COVID-19 vaccines, treatments and variants are unknown, for most people, we may be in a “sweet spot” of the least severe variant to date being met with the greatest vaccine immunity provided so far. If this is true, this wouldn’t support a “delay infection” strategy.
That said, there may be certain situations or certain groups of people who warrant the adoption of either a temporary or indefinite “delay infection” strategy. The use of P2 masks in public could form a useful part of this strategy. It could also be useful for an additional purposes explained below – reducing viral loads.
The routine use of a P2 mask in public could be worthwhile if you wish to pursue a “delay infection” strategy (defined above) either temporarily or indefinitely.
Temporarily Delaying Infection
Examples where you may wish to pursue a temporary delay infection strategy include, but are not limited to:
Indefinitely Delaying Infection
The main reason why you may wish to indefinitely pursue a delay infection strategy is if you wish to take the gamble that you will be able to successfully avoid infection until new more effective vaccines (e.g. an omicron specific vaccine assuming omicron is still the dominant variant when it is released) or new more effective COVID-19 treatments become widely available in Australia. It’s obviously pretty difficult to estimate what the chance of this occurring is and balance that against slowly waning immunity over time from even boosted vaccination. However you may be prepared to take this gamble if COVID-19 infection may cause serious illness or be life threatening for you because you have advanced age, underlying health conditions or you have a genuine contraindication to full vaccination with all currently available vaccines.
Of course, another reason one may wish to pursue a strategy to indefinitely delay infection is if further evidence in the future suggests the assumptions used above to illustrate the potential futility this strategy turn out to be incorrect (e.g. most Australians don’t contract COVID-19 or that infection combined with vaccination doesn’t provide durable protection against severe disease from future variants).
Reducing Viral Load
There is one other benefit to wearing a P2 mask – if you are wearing a P2 mask at the time of an exposure to COVID-19, it may reduce the viral load (amount of virus) that you inhale into your respiratory system compared to if you were wearing only a standard mask at the time. This might result in a milder infection and reduced chance of hospitalisation or severe complications.
It is hard to quantify exactly how much benefit the average person will receive in this regard from wearing a P2 mask in public, especially given the practical limitations in actually using a P2 mask routinely described above and the chance that COVID-19 infection could easily result from exposures occurring when you are not wearing any mask at all. However it’s safe to say, that the same type of person described above, who would benefit from indefinitely employing a delay infection strategy, is also likely to gain the most benefit from using a P2 mask to reduce viral loads they are exposed to.
In addition other people may choose to use P2 masks for this purpose, specifically in high risk situations where the risk of inhaling a high viral load is increased. This may include when they are present for an extended time period within an indoor space that contains a relatively high number of people (given the size of the room) such as crowded public transport, or a full meeting room, theatre etc.
Not delaying infection does not equal omicron parties
It is important to also note that if you choose not to employ a “delay infection strategy”, this is not a reason to actively seek COVID-19 infection through deliberate exposure to the virus e.g. events such as “omicron parties”. The reason such a strategy is unsafe, is that if you take such conscious steps to actively infect yourself, you are reasonably likely to expose yourself to the highest viral loads and therefore potentially the highest risk of the most severe infection outcomes.
Ultimately fully vaccinated individuals need to strike a nuanced balance between the potential benefits, harms and difficulties involved using a P2 mask as part of a delay infection strategy and decide for themselves. This may not be either a dichotomous or permanent decision and individuals may choose to ratchet up or down their steps to delay infection depending on various societal and personal circumstances and future information released about new COVID-19 variants, vaccines and treatments. Additionally there may be specific high risk situations where people may choose to use the P2 mask.
Like many decisions related to COVID-19 we need to make rationale decisions based on incomplete or imperfect information.
For most people living in environments with rampant COVID-19, using a P2 mask routinely in public will probably only delay infection, not prevent it. Due to the cost, problems with supply of masks, discomfort associated with using a mask properly routinely, and the unclear benefit (and possible downsides) to taking extraordinary measures to delay infection, most people may struggle to willingly or practically adopt the P2 mask path and life will be simpler just sticking with a standard mask.
However there are specific situations and specific groups of vulnerable people that may motivate the use of P2 masks to either temporarily or indefinitely delay COVID-19 infection or reduce viral loads in high risk environments.
If you choose to wear a P2 mask, obtaining a certified mask from a credible supplier and using it properly and routinely is most important to maximise your benefits.