10 Common Mask Misconceptions

10 Common Mask Misconceptions

Although masks have been commonplace in some fields for many years, it’s only recently that the general population has had to adopt the devices as an essential daily item. While the current focus of masks is to prevent the spread of COVID-19, there are also many regions where masks are required year-round due to high concentrations of air pollution.


Since this is the first time many of us have had to don masks, there are a lot of misconceptions and misunderstandings around the devices. Specifically, when they are required, how they work, and who should be wearing them. In this article, we aim to dispel some of these misconceptions that we regularly come across.

While masks have primarily been worn over the past two years to help minimise the spread of viruses, they are also essential when it comes to protecting ourselves from air pollution. As such, this article has included misconceptions from both perspectives. Whether you wear a mask primarily due to COVID or due to air pollution, we hope that this article can provide answers to some common mask myths.

#1. Viral Particles Are Too Small to Be Filtered

There is a common misconception that masks and respirators are ineffective against viral particles due to their size. Viral particles (virions) can often be smaller than 0.1μm (100nm), and the myth that these particles are too small for masks to be effective against has been widely perpetuated. 


However, this is not true. There are two parts to this myth that need to be tackled individually. The first is the belief that the mask filter acts as a sieve that catches particles as they try to pass through holes with a smaller diameter. Instead, masks actually filter using very different methods.  

There are a variety of mechanisms that masks use to filter particles. Interception, where particles moving quickly through the filter come in direct contact with a fibre and get stuck to it. Diffusion, where particles that are slower moving get caught on fibres. Gravitational settling, where larger particles fall due to gravity and settle on fibres. Finally, impaction, where particles directly impact a fibre. Some masks also rely on electrostatic filtration, where particles of the opposite charge are attracted and adhere to fibres.


These mechanisms work in conjunction with one another and ‘catch’ particles as they navigate and try to move through the multiple layers and fibres of a filter. This is contrary to the belief that masks act as sieves and therefore cannot catch smaller particles. Very often, filters are more effective against smaller particles and incur their minimum filtration efficiency on particles around 0.3μm - both smaller and larger particles are filtered more efficiently (source 1).

The second factor that needs to be considered is that viral particles are very rarely naked. That is to say; these particles are seldom in the air by themselves. Instead, they are usually attached to other, larger particles such as droplets from respiratory secretions.

A study was done in 2020 (source 2) that indicated that the minimum size of a respiratory particle-containing SARS-CoV-2 is 4.7μm. While this is only a theoretical result, and particles can get smaller over time (as water evaporates from the particle), it is an indication that the particles that spread viruses are significantly larger than their naked form.

In conjunction, these two factors mean that masks are still effective against even very small virions. This does rely on masks having a capable filter, but provided that the devices have been tested, proven and are worn properly they can provide protection against virions and other small particles.


  1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7805396/
  2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7579175/

Fact: Masks do not act as a sieve, and viral particles are very rarely naked and are often far larger than 100nm. Therefore, a correctly-fitted and certified mask is effective against virions and other small particles.

#2. If I Can Smell Something, the Mask Isn’t Working

This is something that we hear very regularly - ‘I can smell smoke (or another smell) through my mask, therefore it isn’t working!’. This is far from true. Even someone with a perfectly fitted mask with absolutely no leaks will experience a range of smells. This does not mean that the mask isn’t effectively filtering particles though. 

As mentioned in the first section, filtration mechanisms allow for more efficient filtering of small particles. However, once particles become extremely small, filtration efficacy begins to drop off. For example, Sulfur has an approximate molecule diameter of 0.0004μm (0.4 nm) and is detectable as a smell (source 1).

Another popular example is farts - if someone farts, and I can smell it, surely that indicates that the mask is not working?! Quite the contrary! One of the Sulfur-containing molecules that are expelled when we fart is methanethiol, a molecule with a diameter of around 0.4nm. This molecule is one that humans can smell.

These particles are extremely small, and masks regularly won’t filter them. However, keep in mind, the air still has to pass through the mask as we need to be able to breathe. Extremely small particles are therefore also able to pass through the mask.

The critical factor to remember here is that COVID particles are around 0.1μm (100nm), and expelled respiratory droplets are far larger (source 2). Smells containing molecules are a tiny fraction of this size. Therefore, even a correctly fitting mask is likely to let smells through.

This does not mean that your mask isn’t filtering what it should. With COVID particles being around 25,000% larger than these smellable molecules, our masks can still be effectively filtering viral particles while allowing smells through. PM1.0 particles are even larger at 250,000% larger than these tiny molecules! 

1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7447000/
2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7224694/

    Fact: Smellable particles can be FAR smaller than both viral particles and fine dust from air pollution. Even a correctly fitted mask with no leaks will allow some smells through as these particles are so incredibly small (even compared to virions). 

    #3. Non-N95 Respirators are Ineffective

    This is another common misconception that we hear every few days. There is a thought that masks and respirators outside of NIOSH-rated N series (N95, N99 and N100) devices either provide lower or no protection against fine particles.

    While it is true that there are many devices on the market that provide lower filtration and protection than N95 respirators, there are also many masks that have undergone extensive testing and have proven to be as effective. In some cases, they are even more effective!

    There are a few important factors to remember here. Firstly, N95 devices require fit-testing to provide the rated protection. A general user can’t purchase such a mask and get the same protection that a medical or industrial professional who has undergone training can. 

    Secondly, the N95 standard is unobtainable by many companies and products due to the high cost of the testing process. On top of this, many masks can’t obtain the rating due to other factors such as their shape. Further, outside of professional applications, there is no need for masks to be certified N95. This leads to many mask companies skipping the N95 certification process as it is either unnecessary or impossible to undergo.

    All of this is to say that just because a mask doesn’t have an N95 certification, it doesn’t mean that it is ineffective at protecting the wearer from fine particles. Rather, look into the other testing data and reports that the device has. From these reports, you will be able to find the capabilities of a mask, including the filtration that it is capable of. 

    Some certification processes (such as the KN95 process) are more applicable to general consumers as the process requires total inward leakage of a range of mask samples to be tested on test subjects. This testing shows that the masks have an acceptable total inward leakage on various faces and is more applicable to general consumers who don’t have fit training.

    Fact: There are many standards and certifications outside of N95 that indicate the capabilities of a mask. Masks can be effective without the N95 certification.

    #4. Reusable Masks Are Inferior to Respirators

    Tagging on from the previous point, there is also a misconception that reusable masks are inferior to respirators in the level of protection they afford the wearer. This is very often not true for the factors discussed above - respirators require fit testing to achieve the best protection. On the other hand, reusable masks such as AirPop are designed from the ground up to fit a variety of faces.

    There are now many reusable masks out there that contain better or similarly performing filter media to respirators. While these masks are usually not certified N95, they will usually have publically available filtration test results on the company website. Frequently they will have a KF94 or KN95 certification which indicates a similar level of filtration, total inward leakage, and breathability but is more easily obtainable.

    Perhaps most importantly, however, is that reusable masks are designed to be worn in everyday situations. They are designed to balance comfort and protection, and this makes them actually useable in daily life. Wearing a respirator every day is incredibly uncomfortable!

    Therefore, it’s a misconception that respirators are better than tested and proven reusable masks. Both have their place, and respirators are designed for specialist use. Reusable masks, though, are designed to be worn by everyday people and, when fitted correctly, can provide a good level of protection.

    Fact: Reusable Masks can be similarly effective. Make sure to check for their certifications and third-party lab testing to understand the capabilities of a mask.

    #5. Filtration Is the Most Important Aspect of a Mask

    When it comes to discussing the specifications of a mask, the most common number that is thrown around is the filtration percentage. You’ll often hear brands advertising 99.7% filtration or mentioning how their masks are capable of filtering 99.9% of bacterial particles. 

    However, the truth is that these numbers should not be all that you base your purchasing decisions around. Although these numbers indicate that the mask will provide fantastic filtration in theory, the reality is often very different. Why? Well, there are a few reasons. 

    Firstly, in most reusable masks on the market, these specifications apply only to the filter media that is used within the mask. That means that in the majority of cases, the filtration capabilities of the mask themselves have not been tested - only the filter media within has been.

    This means that these filtration values are more often than not simply theoretical and not the actual protection that you will be receiving from the mask. These results are best-case scenarios in which no other factors exist. 

    The reality, though, is that a range of other variables are very important to consider. Prime among these, and of equal importance to filtration, is the fit of a mask. If a mask doesn’t seal to your face properly, then these impressive filtration numbers are irrelevant. 

    However, it’s much harder to advertise the fit of a mask in a flashy way. It’s much easier to throw around numbers like 99.8% than to discuss the fit of a mask. As a customer, though, it’s vital to make sure that you consider fit equally important to filtration.

    While you can’t judge the fit of a mask without trying it for yourself, make sure to consider factors that influence the fit of a mask before purchasing. For example, does the mask use earloops or a headband? Is the seal silicone or cloth? Is the wire nose piece loose or stiff? These are all factors that need to be considered before purchasing a mask.

    Fact: Filtration capabilities are important, but they aren’t everything. These percentages only apply if the mask fits perfectly and has no leaks. Therefore, fit is of equal importance. Ideally, a mask will have a good fit and high filtration.

    #6. Masks Only Protect the Wearer

    While the original purpose of masks and respirators was to protect the wearer by filtering inhaled air, masks have a dual purpose in preventing the spread of viruses. This purpose is to filter both the air being inhaled and exhaled by the wearer.

    Inhalation protection requires that masks are fitted correctly and ideally have a high filtration efficacy. However, when most commonly worn masks are less effective devices such as surgical masks, and many people don’t know how to properly don and fit a mask, the inhalation protection of masks shouldn’t be relied upon.

    Instead, when everyone wears a mask, many expelled respiratory particles will be caught before becoming airborne. These expelled particles can contain COVID-19 along with other virions and bacterial particles. Further, these particles are their largest when initially expelled, as when water evaporates, respiratory particles often become smaller. This makes exhalation filtration key for the prevention of the spread of viruses.

    Two-way filtration means that a mask will filter the air passing through it in both directions. While this is the case for most masks, some make use of exhalation valves. These valves are designed to filter inhaled air while allowing exhaled air to pass through unfiltered. 

    This design allows for masks to have lower exhalation resistance and to therefore be more comfortable. However, masks that utilise valves are best used when only protection for the wearer is needed (such as for air pollution). When it comes to slowing the spread of a virus, two-way filtration is more effective.

    It’s important to keep in mind that two-way filtration is the biggest strength of masks when it comes to preventing the spread of viruses. This is especially true for masks that lack filtration for ultrafine particles, such as surgical masks. These masks are worn to filter expelled air from exhalation rather than to filter air inhaled by the wearer.

    Fact: Masks without a valve filter both inhaled and exhaled air. If everyone wears a mask, this creates a ‘double layer’ of protection where both the air exhaled by one wearer and the air inhaled by another user are filtered. Therefore, masks protect both the wearer and others around the wearer.

    #7. Masks Are Always Uncomfortable

    One of the biggest complaints that we’ve seen is regarding the comfort of masks. With many people around the world being forced to don masks for the first time over the past two years, a large number of people have realised just how uncomfortable they are. 

    However, this is not always the case. I will concur that wearing a mask is never as comfortable as not wearing one, but within masks, some are far more comfortable than others. Unfortunately, most people never get to experience these more comfortable devices.

    If you’ve experienced respirators such as N95, KN95 and KF94 masks, you will likely have already experienced the discomfort that these devices often bring. The earloops are thin and cause a lot of pain on top of and behind your ears, and the respirators often dig into your face below your eyes. I’m sure we’ve all experienced ‘mask face’ before!

    Since these respirators tend to be the most readily available masks (alongside surgical masks), many people have not experienced anything better. Unfortunately, that leads to the misconception that all masks are uncomfortable. Which, in turn, drives people away from wanting to wear any mask.

    The good news is that there are masks that are far more comfortable out there. These masks become more comfortable by utilising more breathable filters, incorporating thicker earloops (or headbands) into their design, using lightweight materials on the exterior, or through various other factors.

    These innovative designs allow for masks to be significantly more comfortable even after long durations of wear. If you’ve only ever tried standard masks and respirators and have found them uncomfortable, I recommend trying a lightweight, reusable mask that is designed to be worn day to day.

    Fact: Some masks are uncomfortable. While no mask is quite as comfortable as not wearing a mask, many masks have made strives when it comes to comfort. These designs can make even daily wear far more pleasant.

    #8. I Only Need to Wear Masks on Days of High AQI 

    There is a common belief that air pollution levels within an area are consistent. For example, the air pollution in one borough of New York, Brooklyn, is the same as the air pollution in Manhattan. This is often not true though - air pollution, even in nearby areas, can vary greatly. 

    While the scale used above is still very large, air pollution can vary greatly on a more local level. For example, one street can have significantly higher PM2.5 particle concentrations than a street a mere 200 metres away. Likewise, a house located just a few blocks from another may experience concentrations double that of the first house.

    Therefore, while it’s easy to wake up in the morning, check the citywide AQI and then decide whether or not to don a mask for the day, it’s worth investigating further. If the app or website that you use supports it, check the AQI within your district, your suburb, or on an even more local level if available. 

    What causes these vast differences in air pollution levels? Well, one of the biggest differentiators is the traffic within an area. Cars and other vehicles emit fine particulate matter (PM), carbon monoxide, benzene, nitrogen oxides and more. Areas with higher concentrations of such vehicles are therefore exposed to higher levels of air pollution. 

    Other factors that can significantly impact air pollution on a micro-scale are weather patterns and locality to high pollution emitting sources such as factories.
    Local air pollution is essential to consider if you bike or walk to work or school along a busy road or highway. If this is the case, it’s often worth donning a mask, even if the AQI you see on your app or website is deemed acceptable. 

    If you’re particularly interested in investigating local air pollution levels to judge whether or not you should be donning a mask, you can also pick up portable air pollution monitoring devices. While these devices are often not totally accurate, they are helpful for identifying air quality trends.

    Fact: Local air pollution can vary greatly. Even when a greater area such as a city or district has a low AQI, it’s worth investigating on a more local level. A mask may be a great benefit if you commute via a major highway or other pollution-emitting sources.

    #9. Masks Are Only for Sensitive Groups (Asthma, Respiratory Conditions, Etc)

    There is a common misconception about masks when it comes to who should be wearing them. In particular, there is a thought that masks are only needed for sensitive groups such as people with respiratory conditions like asthma. However, this couldn’t be further from the truth.

    While it’s true that groups suffering from such conditions are likely to have exacerbated symptoms from air pollution, there is no denying that air pollution is harmful to everyone. There are thousands of studies showing that air pollution impacts us all. The Guardian put together an article outlining how air pollution can damage every organ in the human body (source 1).

    I mention this point not to create fear but rather to point out that air pollution impacts us all. Since masks are currently our only defence against air pollution on a personal level, we should all be considering them. They are not devices only needed by sensitive groups.

    If you are lucky enough to live in a smaller town or the country, you are likely experiencing less air pollution than your urban counterparts. However, I recommend that everyone finds a way to check their local air quality - whether from an AQI app or with a portable measurement device. You might be surprised at the local air pollution levels!

    From there, it’s possible to judge whether or not you should be donning a mask and on what days you need to do so. But, in the long run, simply being aware of air pollution can greatly benefit your health.

    Since air pollution is now accepted in many regions of the world, we often don’t consider it at all. Yet, it’s something that is always there and something that doesn’t impact our day to day lives and is therefore forgotten.
    However, it is also a factor that needs to be considered because it can have a long-lasting impact on our lives. Again, it’s not something that we should be scared of. It is something we should all be aware of, though. Masks are not only for sensitive groups; they are for everyone.

    1. https://www.theguardian.com/environment/ng-interactive/2019/may/17/air-pollution-may-be-damaging-every-organ-and-cell-in-the-body-finds-global-review

    Fact: Masks are devices that can help us all. Air pollution is a factor that we all need to consider, and masks are currently the only protection we can use on a personal level while on the go. While masks may not be necessary for everyone, they aren’t only for sensitive groups.

    #10. If Your Glasses Fog Up, the mask Isn’t Fitted Correctly

    The final misconception that we want to discuss today is the belief that if your glasses or other eyewear fog up or you visibly see warm air escape your mask, it isn’t fitted correctly.

    Firstly, it should be mentioned that if your mask does allow air to escape when you exhale, you should check for leaks and perform a seal check. It may be leaking! However, if you are confident that the mask is not leaking yet your glasses are still fogging up, there is an explanation for this!

    When you breathe out, the inside of the mask becomes positively pressurised, meaning that the pressure within the mask is greater than the air pressure outside the mask. This leads to the air inside the mask rushing out towards the lower pressure outside air. 

    While most of this air should be passing through the filter, it’s common for some to also escape around the mask seal. When inhaling, the opposite happens, and the air within the mask becomes negatively pressurised. This leads to the mask collapsing as air is pulled in.

    This pulls the mask in towards our face and seals the mask on inhalation. Some medical professionals have found that their glasses fog even after passing a fit test!

    Therefore, while it’s important to check your mask’s seal if your glasses are fogging up or if you can physically feel air escalating, this is not necessarily a sign of an ill-fitting mask.

    Fact: If you’re glasses fog up, this could be an indication of an ill-fitting mask. However, if you perform a seal check and the mask still leaks, this doesn’t necessarily mean that it is leaking or not fitted correctly. When a mask is positively pressurised (on exhalation), air will seek to escape by any means. This can cause the mask to leak. On inhalation, the mask will be pulled towards your face and should collapse.

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