watch: can you really tell if your mask is legit by lighting it on fire?

videos are popping up online telling viewers that if the inner layer of your surgical mask lights on fire when exposed to a flame (versus melting), it’s a sure sign that the mask is poor quality.  

dr. p. ravi selvaganapathy, engineering professor at mcmaster university and the canada research chair in biomicrofluidics, says that while this is a good way to determine if the mask is a knockoff, it won’t actually tell you if the mask itself is high enough quality to filter out viruses or other pathogens.  

“some manufacturers [may be] replacing melt-blown polypropylene , which is the material that you would want to use, with paper,” says selvaganapathy. “and if that is the case, that test will help (i.e., the paper would burn), but even with plastic, there’s a wide range of milestones with different filtration properties.”  

disposable surgical masks are made up of three layers, explains dr. yi zuo, professor of mechanical engineering at the university of hawai`i at mānoa, via email. an inner layer, which absorbs the moisture in our breath as we exhale, a middle filter layer, and an outer layer that protects the filter from the environment.  

melt-blown polypropylene is a relatively cheap fabric that can be made with a microscopic mesh that will be able to filter out many particles that can get us sick. in quality surgical masks, for example, the gaps or pores in the material are only about 20 microns large, says zuo. (for comparison , a white blood cell is about 25 microns large while the diameter of a human hair is about 70 microns.) the fabric may also be made with an electrostatic charge, which acts to prevent particles smaller than 20 microns – like many viruses — from getting through.  

however, just because the material in the mask melts versus catches on fire doesn’t mean it is melt-blown polypropylene. spunbond polypropylene, which selvaganapathy gives as an example, is another material commonly used in masks that doesn’t have a great filtration rating. this material will still melt when it comes into contact with heat — however, it’s not meant to filter out virus particles.  

he says that the only real way to know the quality of the masks is to look for certifications on the packaging. niosh certification , for example, has specific standards for what sorts of airborne particles the masks must filter out. another certification system for consumers (not necessarily healthcare workers), astm , has set expectations for the amount of aerosols and droplets that can pass through from the mask wearer to the outside world, and provides a certain degree of protection from inhaling aerosols from the environment. 

a mask is only as good as its seal
even the best mask on the market won’t prove entirely effective if there isn’t an effective seal all around the nose and mouth. healthcare workers routinely go through a mask fit test to ensure the size of their masks and their methods for putting them on are effective. these masks are also worn extremely tight to the face to ensure that the seal stays put.  

if a mask doesn’t have a proper seal, whether it be an n95 that doesn’t fit the wearer’s face or a surgical mask that is designed for a more comfortable fit, virus particles and other aerosols can easily flow in through the openings, explains selvaganapathy .   

“even if you have the best quality filtration material, you’re not going to get the benefit of the mask because it’s almost like breathing to open air,” he says .  

why bother wearing a mask at all? 
the initial concept of rolling out masks to the general public wasn’t actually about protecting us from inhaling the virus, but rather to stop us from spreading the virus to others. one study , published in nature last september, found that wearing a surgical mask or unvented kn95 mask reduced the particles emitted when speaking by an average of 90 per cent, and when coughing by an average of 74 per cent, compared to no face covering.   (surprisingly, this study also cast some doubt on how effective reusable cloth masks are at stopping exhaled aerosols, but that’s an article for another day.)  

wearing masks also has the added benefit of diffusing our breath that does get through the mask, so it isn’t concentrated on the person standing directly in front of us.  

certifications and polypropylene aside, the effectiveness of wearing masks without a fit test and other controls in place really depends on the people around us. wearing masks to protect others and surrounding ourselves with other people who wear masks diligently is how we provide the most protection for our communities. no fire hazard required.  

emjones@postmedia.com | @jonesyjourn

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