tag:theconversation.com,2011:/nz/topics/kn95-100060/articlesKN95 – The Conversation2022-11-20T15:22:34Ztag:theconversation.com,2011:article/1947262022-11-20T15:22:34Z2022-11-20T15:22:34ZWith COVID, flu and RSV circulating, it’s time to follow the evidence: Return to mask mandates<figure><img src="https://images.theconversation.com/files/495816/original/file-20221117-13-u0jyep.JPG?ixlib=rb-1.1.0&rect=0%2C10%2C3190%2C2069&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Ontario Premier Doug Ford and Health Minister Sylvia Jones in conversation at Queen's Park, the day after Ontario’s chief medical officer of health ‘strongly recommended’ mask wearing.</span> <span class="attribution"><span class="source">THE CANADIAN PRESS/Chris Young</span></span></figcaption></figure><iframe style="width: 100%; height: 100px; border: none; position: relative; z-index: 1;" allowtransparency="" allow="clipboard-read; clipboard-write" src="https://narrations.ad-auris.com/widget/the-conversation-canada/with-covid--flu-and-rsv-circulating--it-s-time-to-follow-the-evidence--return-to-mask-mandates" width="100%" height="400"></iframe>
<p>The number of children and babies with respiratory illnesses currently <a href="https://globalnews.ca/news/9273442/mcmaster-childrens-hospital-patient-crisis-grows/">exceeds the capacity of our health system</a> to care for them. More adult Canadians will die directly of COVID-19 this year <a href="https://public.tableau.com/app/profile/bill.comeau/viz/CanadaCovid19_16636261617930/Dashboard1">than died last year or in 2020</a>. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/495812/original/file-20221117-23-1isdxx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Bar graph showing deaths from COVID in Canada" src="https://images.theconversation.com/files/495812/original/file-20221117-23-1isdxx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/495812/original/file-20221117-23-1isdxx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=260&fit=crop&dpr=1 600w, https://images.theconversation.com/files/495812/original/file-20221117-23-1isdxx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=260&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/495812/original/file-20221117-23-1isdxx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=260&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/495812/original/file-20221117-23-1isdxx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=326&fit=crop&dpr=1 754w, https://images.theconversation.com/files/495812/original/file-20221117-23-1isdxx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=326&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/495812/original/file-20221117-23-1isdxx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=326&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">COVID deaths in 2022 outnumber those in 2020 or 2021.</span>
<span class="attribution"><span class="source">(Bill Comeau)</span></span>
</figcaption>
</figure>
<p>Eight per cent of vaccinated people with COVID infections that don’t require hospitalization <a href="https://doi.org/10.1038/s41591-022-01840-0">end up with long COVID</a>, with each subsequent infection <a href="https://doi.org/10.1038/s41591-022-02051-3">repeating the risk</a>. COVID increases the risk of <a href="https://doi.org/10.1038/s41591-022-01689-3">cardiovascular</a> <a href="https://doi.org/10.1016/S0140-6736(22)01214-4">and</a> <a href="https://www.ecdc.europa.eu/sites/default/files/documents/Prevalence-post-COVID-19-condition-symptoms.pdf">other health</a> <a href="https://doi.org/10.1038/s41591-022-01840-0">problems</a>, enough to cause a stark rise in <a href="https://www.cdc.gov/nchs/nvss/vsrr/covid19/excess_deaths.htm">excess deaths</a> and to <a href="https://www.cdc.gov/nchs/data/vsrr/vsrr023.pdf">shorten life expectancy</a>.</p>
<p>In 2020, when adult intensive care units were at risk of being overwhelmed, we wore masks and accepted restrictions. With pediatric intensive care now at risk, will leaders follow the evidence and tell us to mask up? While federal officials and <a href="https://www.cbc.ca/news/canada/toronto/ontario-dr-kieran-moore-announcement-1.6650571">several provinces are now recommending masks in all indoor public settings</a> — although <a href="https://toronto.ctvnews.ca/ontario-s-top-doctor-goes-against-own-advice-while-maskless-at-toronto-party-1.6159050">Ontario’s Chief Medical Officer of Health Kieran Moore was seen without one at a party</a> — <a href="https://www.ctvnews.ca/canada/what-provinces-and-territories-are-saying-about-mask-mandates-as-covid-19-rsv-flu-cases-rise-1.6157262">there are no returns to mandates for the public yet</a>.</p>
<h2>Wear the best mask available</h2>
<p>We now know that <a href="https://doi.org/10.1073/pnas.2014564118">masks prevent the spread of respiratory diseases</a>; some better than others. </p>
<figure class="align-right ">
<img alt="A young woman wearing a white face masks with overhead ties" src="https://images.theconversation.com/files/495815/original/file-20221117-16-6d6tbj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/495815/original/file-20221117-16-6d6tbj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=427&fit=crop&dpr=1 600w, https://images.theconversation.com/files/495815/original/file-20221117-16-6d6tbj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=427&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/495815/original/file-20221117-16-6d6tbj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=427&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/495815/original/file-20221117-16-6d6tbj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=536&fit=crop&dpr=1 754w, https://images.theconversation.com/files/495815/original/file-20221117-16-6d6tbj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=536&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/495815/original/file-20221117-16-6d6tbj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=536&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A Vitacore CaN99 respirator with overhead elastic; N95s, CaN99 and FFP3 typically provide greater than 90 per cent filtration without formal fit testing.</span>
<span class="attribution"><span class="source">(Gurleen Dulai, Ranmeet Dulai)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The most effective masks, and the only ones recognized as respiratory protection by formal standards, are respirator masks: N95s, CaN99s, FFP3s and reusable elastomeric respirators. In workplaces, respirators are fit-tested to the individual, resulting in greater than 99 per cent protection. </p>
<p>Even without fit testing, respirator masks prevent <a href="https://doi.org/10.1093/annhyg/meq085">more than</a> <a href="https://doi.org/10.1371/journal.pone.0245688">90 per cent</a> <a href="https://doi.org/10.1097/MD.0000000000023709">of particles</a> smaller than one micron from reaching the wearer (submicron particles, the smallest among <a href="https://doi.org/10.1016%2FS2213-2600(20)30323-4">those thought</a> <a href="https://doi.org/10.1080/23744235.2022.2140822">to be</a> <a href="https://doi.org/10.1038/s41564-021-01047-y">relevant</a>).</p>
<p>Respirator masks are relatively expensive — typically a few dollars each — but thanks to Canadian manufacturers, they are <a href="https://www.clothmasks.org/">available</a> and there are no longer concerns about supply chains for front-line workers. They can be safely <a href="https://www.clothmasks.org/extended-use">reused, with good retention of their filtration</a>. New designs are comfortable and fit most faces. </p>
<figure class="align-left ">
<img alt="A young woman wearing a black face mask with ear loops" src="https://images.theconversation.com/files/495818/original/file-20221117-14-4riq8j.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/495818/original/file-20221117-14-4riq8j.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=460&fit=crop&dpr=1 600w, https://images.theconversation.com/files/495818/original/file-20221117-14-4riq8j.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=460&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/495818/original/file-20221117-14-4riq8j.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=460&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/495818/original/file-20221117-14-4riq8j.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=578&fit=crop&dpr=1 754w, https://images.theconversation.com/files/495818/original/file-20221117-14-4riq8j.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=578&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/495818/original/file-20221117-14-4riq8j.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=578&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A KN95/KF94 mask with ear loops typically provides about 70 per cent filtration.</span>
<span class="attribution"><span class="source">(Gurleen Dulai, Ranmeet Dulai)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>N95s are secured with overhead attachments, providing a good seal at the edges. KN95s and KF94s have excellent filtration material, but their ear loops do not provide as secure a seal, and <a href="https://doi.org/10.1371/journal.pone.0258191">their filtration</a> is <a href="https://doi.org/10.1371/journal.pone.0245688">around 70 per cent</a>. A certified medical mask with a well-fitted cloth mask over it, preferably with overhead ties, provides <a href="https://doi.org/10.1038/s41591-022-01840-0">comparable</a> <a href="https://doi.org/10.1016/j.ajic.2021.10.041">filtration</a> at lower cost.</p>
<figure class="align-right ">
<img alt="A young woman wearing a cloth face mask over a surgical mask" src="https://images.theconversation.com/files/495821/original/file-20221117-27-lavqq2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/495821/original/file-20221117-27-lavqq2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/495821/original/file-20221117-27-lavqq2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/495821/original/file-20221117-27-lavqq2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/495821/original/file-20221117-27-lavqq2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/495821/original/file-20221117-27-lavqq2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/495821/original/file-20221117-27-lavqq2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A well-fitting cloth mask over a certified medical mask typically produces about 70 per cent filtration.</span>
<span class="attribution"><span class="source">(Gurleen Dulai, Ranmeet Dulai)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Certified Level 1 medical masks alone do not fit well, which affects their filtration ability because unfiltered air passes around the edges with every breath. In tests on humans, these have <a href="https://doi.org/10.1371/journal.pone.0264090">typically </a><a href="https://doi.org/10.1371/journal.pone.0245688">filtered </a><a href="https://doi.org/10.1001/jamainternmed.2020.8168">at around 50 per cent</a>, similar to <a href="https://doi.org/10.1016/j.mayocp.2020.07.020">well-designed</a> <a href="https://doi.org/10.1371/journal.pone.0264090">two-layer cotton cloth masks, ideally with overhead ties</a>; both are around 50 per cent.</p>
<p>Poorly fitting <a href="https://doi.org/10.1016/j.ajic.2021.10.041">cloth masks</a> and non-certified procedure masks are likely worse than 50 per cent, but better than nothing. The World Health Organization advises: “<a href="https://www.who.int/emergencies/diseases/novel-coronavirus-2019/advice-for-public/when-and-how-to-use-masks">Make wearing a mask a normal part of being around other people</a>,” to which we would add: wear the best mask available.</p>
<figure class="align-left ">
<img alt="A young woman wearing a blue surgical face mask" src="https://images.theconversation.com/files/495823/original/file-20221117-23-agh7u5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/495823/original/file-20221117-23-agh7u5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=514&fit=crop&dpr=1 600w, https://images.theconversation.com/files/495823/original/file-20221117-23-agh7u5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=514&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/495823/original/file-20221117-23-agh7u5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=514&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/495823/original/file-20221117-23-agh7u5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=646&fit=crop&dpr=1 754w, https://images.theconversation.com/files/495823/original/file-20221117-23-agh7u5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=646&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/495823/original/file-20221117-23-agh7u5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=646&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A Level 1 certified mask provides filtration around 50 per cent because of visible gaps and poor fit. To test fit, breathe out rapidly and feel for air leaks around the mask with your hands.</span>
<span class="attribution"><span class="source">(Gurleen Dulai, Ranmeet Dulai)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The filtration data above are mirrored by epidemiologic data showing that <a href="http://dx.doi.org/10.15585/mmwr.mm7106e1">protection correlates with mask type</a>. In studies of source control (prevention of contamination of the air by respiratory particles), the same hierarchy of efficiency is seen, with N95s at the top. N95s with exhalation valves are an exception and should not be used to prevent spread of respiratory diseases.</p>
<p><a href="https://doi.org/10.1136/bmj-2021-068302">Masks protect </a><a href="https://doi.org/10.1073/pnas.2014564118">against COVID-19</a> and other respiratory infections. They are also an <a href="https://doi.org/10.7326/M20-6625">ideal tool to counter COVID variants</a>, as well as <a href="https://theconversation.com/influenza-and-covid-19-whats-in-store-for-the-fall-winter-respiratory-virus-season-193076">RSV and influenza</a>. Working on basic physical principles — <a href="https://doi.org/10.7326/M20-6625">impaction, sedimentation and diffusion</a> — they protect regardless of the variant or strain. </p>
<p>Staying home when sick is helpful, but many people are infectious <a href="https://doi.org/10.1186/s12879-022-07440-0">before they have symptoms, or never have symptoms</a>. Wearing a mask to prevent infected particles from reaching the environment is basic pollution management: control is best at the source. </p>
<p>Wearing a mask to protect the individual, once controversial, is now settled by <a href="https://www.clothmasks.org/mask-hierarchy">filtration science</a> and <a href="http://dx.doi.org/10.15585/mmwr.mm7106e1">epidemiology</a>. The impact of mask mandates in countries where spontaneous mask wearing was low was repeatedly demonstrated, proving that masks protect us all.</p>
<h2>Why people aren’t wearing masks</h2>
<p>Why aren’t people wearing masks? Some remember the <a href="https://doi.org/10.1111/1467-9566.13525">inconsistency of the advice</a> early in the pandemic. Masks may be conflated with closures and capacity restrictions and the resulting hardships. Whatever the reason — <a href="https://www.theguardian.com/world/2021/oct/26/the-great-cover-up-why-the-uk-stopped-wearing-face-masks">stigma, peer pressure or concern about virtue signalling</a> — countries outside Asia do not have a mask-wearing culture. </p>
<figure class="align-center ">
<img alt="Infographic summarizing the literature on filtration properties of respirators and masks." src="https://images.theconversation.com/files/495814/original/file-20221117-27-xjcwhn.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/495814/original/file-20221117-27-xjcwhn.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=776&fit=crop&dpr=1 600w, https://images.theconversation.com/files/495814/original/file-20221117-27-xjcwhn.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=776&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/495814/original/file-20221117-27-xjcwhn.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=776&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/495814/original/file-20221117-27-xjcwhn.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=976&fit=crop&dpr=1 754w, https://images.theconversation.com/files/495814/original/file-20221117-27-xjcwhn.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=976&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/495814/original/file-20221117-27-xjcwhn.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=976&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Infographic summarizing the literature on filtration properties of respirators and masks.</span>
<span class="attribution"><span class="source">(Shiblul Hasan)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Under these circumstances, it will likely take more than strong recommendations to achieve the <a href="https://doi.org/10.1073/pnas.2014564118">high uptake of mask use that will be most effective</a> in reducing transmission of respiratory viruses. Masks protect individuals, imperfectly. Mask mandates (or high voluntary use of masks) protect populations.</p>
<p>Bringing back mask mandates with unequivocal signalling from governments about the effectiveness of both masks and mask mandates would be the best immediate response to our current crisis. <a href="https://doi.org/10.1038/s41398-022-01814-3">Confidence that mask-wearing is effective correlates geographically with willingness to wear a mask</a>: in time, we hope knowledge will change culture. Strong communication from political and public health leadership would increase community understanding that the minor inconvenience of wearing a mask in public indoor spaces is justified by the death and disability prevented. </p>
<p>In North America, the strategy of using masks according to personal judgment has predictably failed, the strategy of strongly recommending masks is unproven, and it’s too late to experiment. Mask mandates, however, are backed by strong evidence of effectiveness in <a href="https://www.nber.org/papers/w27891">both Canada</a> and the <a href="https://doi.org/10.1377/hlthaff.2020.00818">United States</a>. </p>
<p>Mask mandates are less damaging to a recovering economy than physical distancing and capacity limits, and less damaging to learning than a return to remote schooling.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/495824/original/file-20221117-25-ga6i04.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two line graphs showing relationship between school openings, mask use and community COVID 19 cases and deaths" src="https://images.theconversation.com/files/495824/original/file-20221117-25-ga6i04.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/495824/original/file-20221117-25-ga6i04.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=249&fit=crop&dpr=1 600w, https://images.theconversation.com/files/495824/original/file-20221117-25-ga6i04.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=249&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/495824/original/file-20221117-25-ga6i04.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=249&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/495824/original/file-20221117-25-ga6i04.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=313&fit=crop&dpr=1 754w, https://images.theconversation.com/files/495824/original/file-20221117-25-ga6i04.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=313&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/495824/original/file-20221117-25-ga6i04.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=313&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The relationship between mode of school opening (remote, hybrid and in-person) and mask use at school with community cases and deaths, based on county-level data in the U.S.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.1073/pnas.21034201">(Chernozhukov et al, PNAS 2021:118;e2103420118)</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Schools and universities represent a particularly important opportunity. COVID spreads between children in schools <a href="https://doi.org/10.1073/pnas.2103420118">to infect the whole population; this is mitigated by mask wearing</a>. After Massachusetts lifted its mask mandate, school boards did so at different times, creating a natural experiment: <a href="https://doi.org/10.1056/NEJMoa2211029">transmission was higher among students and staff where mandates were lifted</a> compared with where they were still in place. </p>
<p>There is <a href="https://web.archive.org/web/20220826213955/https:/healthychildren.org/English/health-issues/conditions/COVID-19/Pages/Do-face-masks-interfere-with-language-development.aspx">no convincing</a> <a href="https://www.cdc.gov/coronavirus/2019-ncov/science/science-briefs/masking-science-sars-cov2.html">evidence</a> to date that masks reduce social or language skills. Decreasing spread in schools would increase learning by reducing student and teacher sick days and preserving in-person instruction. Keeping children in schools <a href="https://www.washingtonpost.com/business/2022/11/15/work-absences-childcare/">keeps parents at work</a>.</p>
<p>Mask mandates will not produce a rapid fix of our current problems with respiratory viruses. Indicators will lag by weeks. Until we have a <a href="https://doi.org/10.1038/s41586-022-05398-2">whole-of-society approach</a> that recognizes that <a href="https://doi.org/10.1016/S0140-6736(21)00869-2">COVID is airborne</a>, mask mandates offer us the best immediate opportunity to preserve our health-care system, mitigate death and disability from respiratory viruses, support the economy and safely maintain social contacts in our private lives. </p>
<p><em>Rebecca Rudman, co-founder of the Windsor Essex Sewing Force and member of McMaster’s Cloth Mask Knowledge Exchange, co-authored this article.</em></p><img src="https://counter.theconversation.com/content/194726/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Catherine Clase is editor-in-chief of clothmasks.org and a member of the Cloth Mask Knowledge Exchange, a research and knowledge translation group that includes industry stakeholders. Industry stakeholders contribute to the Cloth Mask Knowledge Exchange by contributing to grant funding, and through in-kind contributions of time and expertise. Industry stakeholders make masks and distribute polypropylene and other fabrics. They may potentially benefit from this article. She is a member of McMaster's Centre of Excellence in Protective Equipment and Materials. Catherine has received consultation, advisory board membership or research funding from the Ontario Ministry of Health, Sanofi, Pfizer, Leo Pharma, Astellas, Janssen, Amgen, Boehringer-Ingelheim and Baxter. In 2018 she co-chaired a KDIGO potassium controversies conference sponsored at arm's length by Fresenius Medical Care, AstraZeneca, Vifor Fresenius Medical Care, Relypsa, Bayer HealthCare and Boehringer Ingelheim. Catherine Clase receives funding from CIHR, and is a member of the Green Party, the American Society of Nephrology, the Canadian Society of Nephrology, the American Association of Textile Chemists and Colorists and ASTM International.</span></em></p><p class="fine-print"><em><span>Charles-Francois de Lannoy receives funding from the Natural Sciences and Engineering Research Council (NSERC) of Canada, the Global Water Futures (GWF) Research organization, Ontario Centres of Excellence (OCE), Federal Economic Development Agency for Southern Ontario (FedDev), Canadian Foundation for Innovation (CFI), the French Embassy, and McMaster University. He has received funding in partnership with Pall Water, Trojan Technologies, Hatch Ltd., and PW Fabrication. He has engaged in various research projects and testing/validation of facemasks for several private companies in Ontario. He is affiliated with the Cloth Mask Knowledge Exchange as an expert advisor.</span></em></p><p class="fine-print"><em><span>Ken G. Drouillard receives funding from Natural Sciences and Engineering Research Council (NSERC) of Canada, Environment and Climate Change Canada, Ontario Ministry of Environment, Conservation and Parks and Mitacs. He is affiliated with the WE-Spark Health Institute, Detroit River Canadian Cleanup Committee, International Association of Great Lakes Research, Editor of Bulletin of Environmental Contamination and Toxicology and science advisor for Windsor-Essex Sewing Force. </span></em></p>In 2020, with adult ICUs at risk of being overwhelmed, we wore masks and accepted restrictions. Now pediatric intensive care is at risk. Will leaders follow the evidence and tell us to mask up?Catherine Clase, Professor of Medicine, Epidemiologist, Physician, McMaster UniversityCharles-Francois de Lannoy, Associate Professor, Chemical Engineering, McMaster UniversityKen G. Drouillard, Professor, Great Lakes Institute for Environmental Research, School of the Environment, University of WindsorLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1815822022-04-20T19:36:25Z2022-04-20T19:36:25ZShould you wear a mask on a plane, bus or train when there’s no mandate? 4 essential reads to help you decide<figure><img src="https://images.theconversation.com/files/458911/original/file-20220420-25-qleeh8.jpg?ixlib=rb-1.1.0&rect=187%2C130%2C5120%2C3082&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">It is now up to individuals whether to wear masks in airports and other mass transit areas.</span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/TravelMaskMandate/28ce57b3790b493190c8409bf0cd06d0/photo?Query=mask%20plane&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=469&currentItemNo=22">AP Photo/Evan Vucci</a></span></figcaption></figure><p>On April 18, 2022, a judge in Florida <a href="https://www.cnn.com/us/live-news/federal-mask-mandate-airlines-04-19-22/index.html">struck down the federal mandate requiring passengers on mass transit to wear masks</a>. While the U.S. Centers for Disease Control and Prevention still recommends that passengers mask up while on planes, trains or buses, it is no longer a requirement. When asked whether people should wear masks on planes, President Joe Biden replied: “<a href="https://www.cnn.com/us/live-news/federal-mask-mandate-airlines-04-19-22/index.html">That’s up to them</a>.”</p>
<p>The Conversation has been covering the science of masks since the beginning of the pandemic. Masking may no longer be required on mass transit, but you can always choose to still wear a mask. For those worried about being exposed to SARS-CoV-2 or developing COVID-19, below are highlights from four articles exploring the benefits of wearing a mask and how to get the most protection from wearing one. </p>
<h2>1. Masks can protect the person wearing them</h2>
<p>A lot of the reason for wearing a mask is to protect others. But early on in the pandemic, <a href="https://profiles.ucsf.edu/monica.gandhi">Monica Gandhi, a professor of medicine</a> at the University of California, San Francisco, explained how masks can protect the wearer, too.</p>
<p>“When you wear a mask – even a cloth mask – you typically are <a href="https://dx.doi.org/10.7326%2FM20-2567">exposed to a lower dose of the coronavirus</a> than if you didn’t,” Gandhi writes. “Both <a href="https://doi.org/10.1073/pnas.2009799117">recent experiments in animal models</a> using coronavirus and nearly a <a href="https://doi.org/10.1038/nri2802">hundred years of viral research</a> show that <a href="https://theconversation.com/cloth-masks-do-protect-the-wearer-breathing-in-less-coronavirus-means-you-get-less-sick-143726">lower viral doses usually mean less severe disease.</a>”</p>
<p>Though it’s only one of many factors, “the amount of virus that you’re exposed to – called the viral inoculum, or dose – has <a href="https://doi.org/10.1038/nri2802">a lot to do with how sick you get</a>. If the exposure dose is very high, the immune response can become overwhelmed,” explains Gandhi. “On the other hand, if the initial dose of the virus is small, the immune system is able to contain the virus.”</p>
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Read more:
<a href="https://theconversation.com/cloth-masks-do-protect-the-wearer-breathing-in-less-coronavirus-means-you-get-less-sick-143726">Cloth masks do protect the wearer – breathing in less coronavirus means you get less sick</a>
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<p>The better the mask, the lower the exposure dose. And in the many months since Gandhi wrote that story, a lot of work has been done to determine which kinds of masks are most effective. </p>
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<a href="https://images.theconversation.com/files/458910/original/file-20220420-18-nanbe4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An N95, surgical and cloth mask." src="https://images.theconversation.com/files/458910/original/file-20220420-18-nanbe4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/458910/original/file-20220420-18-nanbe4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=413&fit=crop&dpr=1 600w, https://images.theconversation.com/files/458910/original/file-20220420-18-nanbe4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=413&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/458910/original/file-20220420-18-nanbe4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=413&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/458910/original/file-20220420-18-nanbe4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=519&fit=crop&dpr=1 754w, https://images.theconversation.com/files/458910/original/file-20220420-18-nanbe4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=519&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/458910/original/file-20220420-18-nanbe4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=519&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Not all masks offer the same amount of filtration.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/protective-face-masks-commonly-used-during-2020-royalty-free-image/1248294245?adppopup=true">Gaelle Beller Studio/Moment via Getty Images</a></span>
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<h2>2. What makes for a good mask?</h2>
<p>The first thing to consider when wearing a mask is whether it’s a good one. <a href="https://scholar.google.com/citations?hl=en&user=MaEhNkQAAAAJ">Christian L'Orange is a professor of mechanical engineering</a> and has been testing different masks for the state of Colorado since the pandemic started. He explains that there are two things that make for a protective mask. “First, there’s the ability of the material to capture particles. The second factor is the fraction of inhaled or exhaled air leaking out from around the mask – essentially, how well a mask fits.”</p>
<p>When it comes to these two attributes, L'Orange says, “<a href="https://theconversation.com/what-is-the-best-mask-for-covid-19-a-mechanical-engineer-explains-the-science-after-2-years-of-testing-masks-in-his-lab-175481">the N95 and KN95 masks are the best option</a>.” This performance has a lot to do with the materials they are made from. “These fibers are very tightly packed together so the gaps a particle must navigate through are very small. This results in a high probability that particles will end up touching and sticking to a fiber as they pass through a mask. These polypropylene materials also often <a href="https://www.thomasnet.com/articles/machinery-tools-supplies/what-is-melt-blown-extrusion/">have a static charge</a> that can help attract and catch particles.”</p>
<p>Fit is the second important factor for a mask. As L'Orange writes, “a mask can offer protection only if it doesn’t leak.” N95s and KN95s are stiff and seal much better than other masks.</p>
<p>If you don’t have access to an N95 or KN95, surgical masks should be your second choice. They are made of densely woven material, but they don’t seal perfectly. Cloth masks should be your last choice because of their generally loose weave and bad fit. But there are ways to improve the performance of surgical and cloth masks. </p>
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Read more:
<a href="https://theconversation.com/what-is-the-best-mask-for-covid-19-a-mechanical-engineer-explains-the-science-after-2-years-of-testing-masks-in-his-lab-175481">What is the best mask for COVID-19? A mechanical engineer explains the science after 2 years of testing masks in his lab</a>
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<h2>3. How to make a mask fit well</h2>
<p>“No matter how good a mask’s material is, it won’t work well if it doesn’t fit well,” writes <a href="https://scholar.google.com/citations?user=fZJWmF8AAAAJ&hl=en&oi=ao">Scott Schiffres, a mechanical engineer</a> at Binghamton University.</p>
<p>There are <a href="https://theconversation.com/cdc-says-masks-must-fit-tightly-and-two-are-better-than-one-153778">two ways to improve the fit and performance of surgical and cloth masks</a>. The first, explains Schiffres, is simply wearing two masks. “Double-masking is wearing a cotton mask over a medical-procedure mask.” This can greatly improve the fit and add a little bit more filtration. The second approach is to knot and tuck a surgical mask so that it fits better. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/OD-jy7M6tEc?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Knotting and tucking a surgical mask can make it fit much better.</span></figcaption>
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<p>As Schiffres explains in his article, “Knotting and tucking entails tying a knot in the elastic loops that go over your ears, close to where they attach to the mask. Then, you tuck the extra mask fabric into the gap that is often present where the ear loops attach to the mask, and flatten that part as much as possible. Both of these tricks make a better fit and <a href="https://www.cdc.gov/mmwr/volumes/70/wr/mm7007e1.htm?s_cid=mm7007e1_w">decrease the mask-wearers’ exposure to potentially infectious aerosols by 95%</a> as compared with wearing no mask at all. That’s a <a href="https://doi.org/10.1017/dmp.2013.43">15% improvement over the 80% efficiency found when using a single surgical mask</a>.</p>
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<p>
<em>
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Read more:
<a href="https://theconversation.com/cdc-says-masks-must-fit-tightly-and-two-are-better-than-one-153778">CDC says masks must fit tightly – and two are better than one</a>
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<h2>4. Breakthrough cases and new variants</h2>
<p>The final consideration when deciding to wear a mask isn’t about you. Doing so can protect others. </p>
<p><a href="https://scholar.google.com/citations?user=XY7DNtgAAAAJ&hl=en&oi=ao">Sara Sawyer</a>, <a href="https://www.colorado.edu/pac/arturo-barbachano-guerrero">Arturo Barbachano-Guerrero</a> and <a href="https://scholar.google.com/citations?user=l2lpnYkAAAAJ&hl=en&oi=ao">Cody Warren</a> are virologists and biologists at the University of Colorado Boulder. In <a href="https://theconversation.com/alpha-then-delta-and-now-omicron-6-questions-answered-as-covid-19-cases-once-again-surge-across-the-globe-174703">a recent story</a>, they write that omicron "is often able <a href="https://doi.org/10.1038/s41586-021-04385-3">to evade existing immunity</a> long enough to start an infection, cause symptoms and transmit onward to the next person.” “This explains why reinfections and vaccine <a href="https://www.cdc.gov/coronavirus/2019-ncov/vaccines/effectiveness/why-measure-effectiveness/breakthrough-cases.html">breakthrough infections</a> seem to be more common with omicron.”</p>
<p>Case numbers are low for now, and therefore so is the risk of catching or transmitting the coronavirus. But it is not zero; some places have higher risk than others, and new variants can come on quickly. As the team writes, all new variants that spread widely – so-called <a href="https://www.cdc.gov/coronavirus/2019-ncov/variants/variant-classifications.html#anchor_1632154493691">variants of concern</a> – are likely to be highly transmissible.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/alpha-then-delta-and-now-omicron-6-questions-answered-as-covid-19-cases-once-again-surge-across-the-globe-174703">Alpha then delta and now omicron – 6 questions answered as COVID-19 cases once again surge across the globe</a>
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<hr>
<p>The person next to you on the plane might not be wearing a mask and, as it stands, that is their choice to make. If you want to lower your own chances of catching or spreading the coronavirus, there are still a number of reasons to wear a well-fitting, high-quality mask. </p>
<p><em>Editor’s note: This story is a roundup of articles from The Conversation’s archives.</em></p><img src="https://counter.theconversation.com/content/181582/count.gif" alt="The Conversation" width="1" height="1" />
Despite the halt to the federal mask mandate for mass transit, people may still choose to protect themselves. For those who do, the type of mask and how well it fits matter.Daniel Merino, Associate Breaking News Editor and Co-Host of The Conversation Weekly PodcastLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1754812022-01-25T19:43:00Z2022-01-25T19:43:00ZWhat is the best mask for COVID-19? A mechanical engineer explains the science after 2 years of testing masks in his lab<figure><img src="https://images.theconversation.com/files/442356/original/file-20220124-13-tvy45q.jpg?ixlib=rb-1.1.0&rect=0%2C700%2C5592%2C2859&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Not all masks offer the same level of protection for you and those around you.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/high-angle-view-of-masks-on-white-background-royalty-free-image/1226906207?adppopup=true">Martin Barth/EyeEm via Getty Images</a></span></figcaption></figure><p><em>The Centers for Disease Control and Prevention has changed its guidelines about masks and respirators a number of times over the past two years and gave its most recent update on Jan. 14, 2022. The update states that cloth face coverings offer the least protection from the coronavirus compared with surgical masks or N95-style masks. <a href="https://scholar.google.com/citations?user=MaEhNkQAAAAJ&hl=en&oi=ao">Christian L'Orange is a mechanical engineer</a> who has been testing the performance of masks for the state of Colorado since the beginning of the pandemic. He explains the new CDC guidelines and the science of what makes for a good mask.</em></p>
<h2>1. What changed in the CDC guidelines?</h2>
<p>The CDC <a href="https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/types-of-masks.html">currently recommends</a> that you “wear the most protective mask you can that fits well and that you will wear consistently.” The question, then, is what type of mask offers the best protection for you – by filtering the air you breathe in – and for those around you – by filtering the air you breathe out?</p>
<p>The CDC’s updated guidelines clearly lay out the <a href="https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/types-of-masks.html">hierarchy of protection</a>: “Loosely woven cloth products provide the least protection, layered finely woven products offer more protection, well-fitting disposable surgical masks and KN95s offer even more protection, and well-fitting NIOSH-approved respirators (including N95s) offer the highest level of protection.”</p>
<p>From a performance standpoint, the <a href="https://doi.org/10.1093/annhyg/meq044">N95 and KN95 masks are the best option</a>. While <a href="https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/cloth-face-cover-guidance.html">supply chain limitations</a> led to the CDC recommending people not wear N95s early in the pandemic, today they are easily obtainable and should be your first choice if you want the most protection. </p>
<p>The biggest change in the new guidelines has to do with cloth masks. Previous guidance from the CDC had said that some cloth masks could offer <a href="https://www.cdc.gov/coronavirus/2019-ncov/science/science-briefs/masking-science-sars-cov2.html">acceptable levels of protection</a>. The new guidance still acknowledges that cloth masks can offer a small amount of protection but places them at the very bottom of the bunch.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/442355/original/file-20220124-21-3h1min.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A tangled mass of fibers, as seen through a microscope." src="https://images.theconversation.com/files/442355/original/file-20220124-21-3h1min.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/442355/original/file-20220124-21-3h1min.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/442355/original/file-20220124-21-3h1min.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/442355/original/file-20220124-21-3h1min.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/442355/original/file-20220124-21-3h1min.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/442355/original/file-20220124-21-3h1min.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/442355/original/file-20220124-21-3h1min.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">N95 masks are made from a tangled web of tiny plastic fibers that are very effective at trapping particles.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:%D0%92%D0%BD%D0%B5%D1%88%D0%BD%D0%B8%D0%B9_%D1%81%D0%BB%D0%BE%D0%B9_%D0%BC%D0%B5%D0%B4%D0%B8%D1%86%D0%B8%D0%BD%D1%81%D0%BA%D0%BE%D0%B9_%D0%BC%D0%B0%D1%81%D0%BA%D0%B8_(%D0%BF%D0%BE%D0%BB%D1%8F%D1%80%D0%B8%D0%B7%D0%B0%D1%86%D0%B8%D1%8F).jpg#/media/File:%D0%92%D0%BD%D0%B5%D1%88%D0%BD%D0%B8%D0%B9_%D1%81%D0%BB%D0%BE%D0%B9_%D0%BC%D0%B5%D0%B4%D0%B8%D1%86%D0%B8%D0%BD%D1%81%D0%BA%D0%BE%D0%B9_%D0%BC%D0%B0%D1%81%D0%BA%D0%B8_(%D0%BF%D0%BE%D0%BB%D1%8F%D1%80%D0%B8%D0%B7%D0%B0%D1%86%D0%B8%D1%8F).jpg">Alexander Klepnev via Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>2. What’s the difference between N95, surgical and cloth mask materials?</h2>
<p>The effectiveness of a mask – how much protection a mask provides the wearer – is a combination of two major elements. First, there’s the ability of the material to capture particles. The second factor is the fraction of inhaled or exhaled air leaking out from around the mask – essentially, how well a mask fits. </p>
<p>Most mask materials can be thought of as a tangled net of small fibers. Particles passing through a mask are stopped when they physically touch one of those fibers. N95s, KN95s and surgical masks are purpose-built to be effective at removing particles from air. Their fibers are typically made from melt-blown plastics, often polypropylene, and the strands are tiny – often less than <a href="https://doi.org/10.1016/B978-185617375-9/50004-3">four thousandths of an inch (10 micrometers) in diameter</a> – or approximately one third the width of a human hair. These small fibers create a large amount of surface area within the mask for filtering and collecting particles. Although the specific construction and thickness of the materials used in N95, KN95 and surgical masks can vary, the filter media used are often quite similar.</p>
<p>These fibers are very tightly packed together so the gaps a particle must navigate through are very small. This results in a high probability that particles will end up touching and sticking to a fiber as they pass through a mask. These polypropylene materials also often have a <a href="https://www.thomasnet.com/articles/machinery-tools-supplies/what-is-melt-blown-extrusion/">static charge</a> that can help attract and catch particles. </p>
<p>Cloth masks are typically made of common woven materials such as cotton or polyester. The fibers are often large and less densely packed together, meaning particles can <a href="https://doi.org/10.1021/acsnano.0c05025">easily pass through the material</a>. Adding more layers can help, but stacking layers has a <a href="https://doi.org/10.1080/02786826.2020.1817846">diminishing return</a> and the performance of a cloth mask, even <a href="https://jv.colostate.edu/masktesting/">with multiple layers</a>, will still typically not match that of surgical mask or N95.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/442358/original/file-20220124-27-1ch5axg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A side view of man wearing a surgical mask" src="https://images.theconversation.com/files/442358/original/file-20220124-27-1ch5axg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/442358/original/file-20220124-27-1ch5axg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/442358/original/file-20220124-27-1ch5axg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/442358/original/file-20220124-27-1ch5axg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/442358/original/file-20220124-27-1ch5axg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/442358/original/file-20220124-27-1ch5axg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/442358/original/file-20220124-27-1ch5axg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Surgical masks are made of good materials but are hard to seal against the face and often allow air to escape past a person’s cheeks.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/men-wear-masks-to-prevent-pollution-pollution-royalty-free-image/1186031353?adppopup=true">Krisanapong Detraphiphat/Moment via Getty Images</a></span>
</figcaption>
</figure>
<h2>3. How much does fit matter for masks?</h2>
<p>Fit is the other major component in how effective a mask is. Even if the materials used in a mask were perfect and it removed all particles from the air that passed through it, a mask can offer protection only if it doesn’t leak.</p>
<p>When you breathe in and out, air will always take the path of least resistance. If there are any gaps between a mask and someone’s face, a substantial fraction of every breath will seep out through those gaps and the mask will <a href="https://doi.org/10.1021/acs.est.0c07291">provide relatively little protection</a>. </p>
<p>Many cloth mask designs simply do not seal well. They are not stiff enough to push against the face, there are gaps where the mask doesn’t even come in contact with the face and it is not possible to cinch them tightly enough against the skin to form a decent seal.</p>
<p>But leaking is a concern for all masks. Although the materials used in surgical masks are quite effective, they often bunch and fold on the sides. These gaps provide an easy route for air and particles to leak out. Knotting and tucking surgical masks or wearing a cloth mask over a surgical mask can both <a href="https://www.nytimes.com/article/double-masking-tips-coronavirus.html">significantly reduce leakage</a>.</p>
<p>N95 masks aren’t immune to this problem either; if the nose clip isn’t securely pushed against your face, the mask is leaking. What makes N95s unique is that a <a href="https://www.fda.gov/medical-devices/personal-protective-equipment-infection-control/n95-respirators-surgical-masks-face-masks-and-barrier-face-coverings">specific requirement</a> of the N95 certification process is making sure the masks can form a good seal.</p>
<h2>4. What is different about omicron?</h2>
<p>The mechanics of how masks function is likely no different for omicron than any other variant. The difference is that the omicron variant <a href="https://www.cdc.gov/coronavirus/2019-ncov/variants/omicron-variant.html">is more easily transmitted</a> than previous variants. This high level of infectiousness makes wearing good-quality masks and wearing them correctly to limit the chances of catching or spreading the coronavirus that much more critical.</p>
<p>[<em>Over 140,000 readers rely on The Conversation’s newsletters to understand the world.</em> <a href="https://memberservices.theconversation.com/newsletters/?source=inline-140ksignup">Sign up today</a>.]</p>
<p>Unfortunately, the attributes that make for a good mask are the very things that make masks uncomfortable and not very stylish. If your cloth mask is comfy and light and feels like you are wearing nothing at all, it probably isn’t doing much to keep you and others safe from the coronavirus. The protection offered by a high-quality, well-fitting N95 or KN95 is the best. Surgical masks can be very effective at filtering out particles, but getting them to fit correctly can be tricky and makes the overall protection they will provide you questionable. If you have other options, cloth masks should be a last choice.</p><img src="https://counter.theconversation.com/content/175481/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Christian L'Orange receives funding associated with the testing and evaluation of testing masks including fee-for-service testing and funding from the World Health Organization.</span></em></p>The CDC’s updated mask guidelines say that cloth masks offer the least protection from COVID-19. Differences in the materials masks are made from and the ways they fit are the reason.Christian L'Orange, Assistant Research Professor of Mechanical Engineering, Colorado State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1583572021-05-31T16:17:14Z2021-05-31T16:17:14ZPrepare for the worst: 10 steps to get ready for wildfire smoke<figure><img src="https://images.theconversation.com/files/403394/original/file-20210528-21-1eejtpo.jpg?ixlib=rb-1.1.0&rect=261%2C110%2C6438%2C4355&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">People with a plan feel more empowered and self-reliant during wildfire disasters. They have better mental and physical health outcomes than those who were less prepared.</span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><iframe style="width: 100%; height: 250px; border: none; position: relative; z-index: 1;" src="https://narrations.ad-auris.com/widget/the-conversation-canada/wildfires-are-sure-to-follow-these-heatwaves-so-prepare-for-the-worst-10-steps-to-get-ready-for-wildfire-smoke-" width="100%" height="400"></iframe>
<p>The wildfire season in western North America <a href="https://doi.org/10.1073/pnas.2011048118">keeps setting new records</a> and the <a href="https://www.nationalgeographic.com/environment/article/megadrought-persists-in-western-us-as-another-extremely-dry-year-develops">outlook for the coming summer seems grim</a>.</p>
<p>On top of the concerning environmental conditions, more people are spending more time outdoors due to the ongoing COVID-19 pandemic. Given that <a href="https://doi.org/10.1038/s41598-021-88131-9">most wildfires are caused by human activity</a>, the summer of 2021 has the <a href="https://massivesci.com/notes/wildfire-ecology-2021-moisture/">potential to be worse</a> than any season before it. </p>
<p>The direct threat of wildfire affects people near forests, but smoke can travel for thousands of kilometres to areas far away. Over the past decade, we have experienced prolonged periods when <a href="https://doi.org/10.1088/1748-9326/abf966">millions of people in western North America were breathing unhealthy air due to wildfire smoke pollution</a>. </p>
<p>Exposure to wildfire smoke is associated with a range of acute effects, <a href="https://doi.org/10.1289/ehp.1409277">particularly for those with respiratory diseases</a>. Evidence of <a href="https://doi.org/10.1016/j.envint.2020.105668">longer-term health effects</a> is also starting to emerge.</p>
<p>Outdoor air pollution from vehicles and industry can be reduced though new laws and technologies, but that’s not true for wildfire smoke. In addition, we can’t stop breathing when it’s smoky and it’s not practical to relocate to less smoky locations. </p>
<p>Wildfire smoke is both inevitable and largely unpredictable, so we need to become resilient to smoke by changing our activities and behaviours to limit exposure and protect health. </p>
<h2>10 steps: Planning, air cleaners, masks and more</h2>
<p>Being prepared for smoke episodes before they occur can reduce fear and uncertainty when air quality starts to deteriorate. Research indicates that <a href="https://doi.org/10.1007/s40725-015-0015-7">people with a plan feel more empowered and self-reliant during wildfire disasters</a>, and that they have better mental and physical health outcomes than those who were less prepared. </p>
<p>Here are 10 steps to help you develop a plan for the wildfire smoke season ahead. </p>
<p><strong>1. Understand your household risk.</strong> Some people are more likely to experience negative health effects from smoke, especially those who have <a href="https://www.epa.gov/pm-pollution/how-smoke-fires-can-affect-your-health">asthma, COPD, heart disease, diabetes, other chronic conditions or acute infections such as COVID-19</a>. Pregnant women, infants, young children, older adults are also more sensitive to smoke, and people who work or live outdoors are more exposed. If smoke has made someone feel unwell in the past, it will likely make them feel unwell again. </p>
<p><strong>2. Identify others you want to support.</strong> There may be people outside your household you want to help during a smoke episode, particularly older adults in your family or community. Keep them in mind as you develop your plans. </p>
<figure class="align-center ">
<img alt="homes on fire surrounded by palm trees." src="https://images.theconversation.com/files/402722/original/file-20210525-21-7290uu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/402722/original/file-20210525-21-7290uu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/402722/original/file-20210525-21-7290uu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/402722/original/file-20210525-21-7290uu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/402722/original/file-20210525-21-7290uu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/402722/original/file-20210525-21-7290uu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/402722/original/file-20210525-21-7290uu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Wildfire engulfs homes in the village of Schinos, near Athens, May 19, 2021.</span>
<span class="attribution"><span class="source">(AP Photo/Valerie Gache)</span></span>
</figcaption>
</figure>
<p><strong>3. Review medical management plans.</strong> Anyone who has a chronic disease with a <a href="https://asthma.ca/get-help/living-with-asthma/asthma-action-plan">management plan</a> should consult with their doctor about adapting it for smoky conditions. For example, people with asthma and COPD are particularly sensitive to smoke, and evidence suggests that <a href="https://doi.org/10.1289/EHP5792">smoke can make it more difficult for people with diabetes to balance their insulin</a>. </p>
<p><strong>4. Stock up on rescue medications.</strong> There can be high demand for medications such as inhalers when it gets smoky, and highly sensitive people may be less mobile. It is best to stock up on these medications before the season begins, so they are readily available when needed. Always travel with your rescue medications during wildfire season. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/10-tips-for-coping-with-wildfire-smoke-from-a-public-health-expert-146015">10 tips for coping with wildfire smoke, from a public health expert</a>
</strong>
</em>
</p>
<hr>
<p><strong>5. Consider purchasing a portable air cleaner.</strong> Most people spend <a href="https://www.epa.gov/report-environment/indoor-air-quality">90 per cent of their time inside</a>. Portable air cleaners with HEPA filters can significantly reduce <a href="http://www.bccdc.ca/resource-gallery/Documents/Guidelines%20and%20Forms/Guidelines%20and%20Manuals/Health-Environment/BCCDC_WildFire_FactSheet_PortableAirCleaners.pdf">indoor PM 2.5 concentrations</a> when sized and used properly. There are many options on the market, so do some research to find the best option for your space. <a href="http://www.bccdc.ca/resource-gallery/Documents/Guidelines%20and%20Forms/Guidelines%20and%20Manuals/Health-Environment/BCCDC_WildFire_FactSheet_BoxFanAirFilters.pdf">A high-quality furnace filter taped to a box fan can also be effective in a small room</a>.</p>
<p><strong>6. Get ready to shelter in place.</strong> Think about how to keep the air in your home (or areas of your home, especially bedrooms) cleaner by closing windows, running your forced air system on recirculate and using portable air cleaners. Beware of getting too hot, though — <a href="https://www.canada.ca/en/health-canada/services/publications/healthy-living/infographic-staying-healthy-heat.html">overheating is a bigger health risk than breathing smoke</a> for most people.</p>
<figure class="align-center ">
<img alt="An orange glow over San Francisco." src="https://images.theconversation.com/files/402726/original/file-20210525-17-1dvt4ch.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/402726/original/file-20210525-17-1dvt4ch.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/402726/original/file-20210525-17-1dvt4ch.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/402726/original/file-20210525-17-1dvt4ch.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/402726/original/file-20210525-17-1dvt4ch.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/402726/original/file-20210525-17-1dvt4ch.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/402726/original/file-20210525-17-1dvt4ch.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Thick smoke covered San Francisco in September 2020, giving it a red glow. Small particulates, measuring less than 2.5 microns in diametre (PM 2.5), are linked to increased risk of illness and death.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<p><strong>7. Find good masks for time outdoors.</strong> A well-fitted respirator mask (common types are N95, KN95 and KF94) provides the <a href="https://doi.org/10.1513/AnnalsATS.201812-894PS">best protection from the small particles in wildfire smoke</a>, and these have become easier to find since the COVID-19 pandemic. We have also learned that a <a href="https://doi.org/10.1021/acsnano.0c03252">well-fitting three-layer disposable or cloth mask can do a pretty good job</a>. The fit is key — inhaled air must pass through the material of the mask, not around it. People who work outdoors should consult their occupational health and safety professionals before the season begins. </p>
<p><strong>8. Use technology to your advantage.</strong> Applications such as <a href="https://www.canada.ca/en/environment-climate-change/services/weather-general-tools-resources/weathercan.html">WeatherCAN</a> and <a href="https://open.alberta.ca/interact/aqhi-canada">AQHI Canada</a> (in Canada) and <a href="https://www.airnow.gov/airnow-mobile-app">AirNow</a> and <a href="https://www.epa.gov/air-research/smoke-sense-study-citizen-science-project-using-mobile-app">SmokeSense</a> (in the U.S.) can help you keep track of current conditions and air quality forecasts. Some local agencies provide email and text services to notify subscribers about changing conditions — Google can probably help you find them! </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-wildfire-smoke-affects-pets-and-other-animals-129430">How wildfire smoke affects pets and other animals</a>
</strong>
</em>
</p>
<hr>
<p><strong>9. Bookmark important information.</strong> In the morning, check the <a href="https://weather.gc.ca/firework/index_e.html">FireWork</a>, <a href="https://firesmoke.ca/forecasts/current/">BlueSky</a> and <a href="https://fire.airnow.gov/">AirNow</a> smoke forecasts for the day. These can help you to understand where fires are currently burning, and where the smoke is likely to travel. You can also bookmark tips for coping with smoke when it happens. </p>
<p><strong>10. Connect with others about smoke.</strong> Talk to your family and community about your planning process and help others to think through their own preparations. The more we get ready for smoke before the wildfire season starts, the more resilient we will be when the smoke arrives. </p>
<p>It’s impossible to predict when and where extreme wildfire smoke will occur, but we know that our wildfire seasons are getting longer and more severe. We must head into every new wildfire season by preparing for the worst. It’s not optimistic and it’s not pessimistic — it’s just realistic <a href="https://fas.org/sgp/crs/misc/IF10244.pdf">based on trends over the past decades</a>.</p><img src="https://counter.theconversation.com/content/158357/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sarah Henderson receives funding from the Canadian Institutes of Health Research, BC Lung Association, and Health Canada. </span></em></p><p class="fine-print"><em><span>Mike Flannigan receives funding from the University of Alberta and the Natural Sciences and Engineering Research Council (NSERC) of Canada.</span></em></p>Wildfire smoke is both inevitable and largely unpredictable. We need to change our activities and behaviours to limit exposure to wildfire smoke and protect health.Sarah Henderson, Associate Professor (Partner), School of Population and Public Health, University of British ColumbiaMike Flannigan, Professor of Wildland Fire, University of AlbertaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1559872021-04-21T09:28:49Z2021-04-21T09:28:49ZHigh-filtration masks only work when they fit – so we created a new way to test if they do<figure><img src="https://images.theconversation.com/files/391673/original/file-20210325-13-qiuil3.jpg?ixlib=rb-1.1.0&rect=0%2C161%2C4311%2C3161&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/woman-wearing-face-mask-protect-filter-1525092257">US 2015/Shutterstock</a></span></figcaption></figure><p>During the pandemic, the prevailing thought has been that a high-filtration mask – such as an <a href="https://www.cdc.gov/niosh/npptl/pdfs/UnderstandDifferenceInfographic-508.pdf">N95</a>, <a href="https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/types-of-masks.html">KN95</a> or <a href="https://metro.co.uk/2021/01/27/what-are-ffp3-face-masks-are-they-reusable-and-where-to-get-one-13976291/">FFP3</a> – should offer better protection than a surgical or fabric mask. However, <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0245688">recent research</a> I conducted with colleagues at the University of Cambridge suggests this isn’t necessarily the case. For these masks to be highly protective, they must properly fit the wearer, but often they don’t.</p>
<p>This is itself an issue, but our research also discovered another worrying thing: people aren’t very good at assessing whether their mask fits. Frequently, they use a self-assessment method to check fit, which we found to be unreliable. This suggests people may be acting as though they’re wearing a well-fitting mask when they aren’t, which increases the risk of them catching and spreading the coronavirus.</p>
<p>Given this, we decided to conduct a <a href="https://www.cambridge.org/core/journals/disaster-medicine-and-public-health-preparedness/article/performing-qualitative-mask-fit-testing-without-a-commercial-kit-fit-testing-which-can-be-performed-at-home-and-at-work/41EDE04D0885104F2ECBF5725047D7C8">second piece of research</a>, to see if we could improve the fit-checking method. This resulted in us creating a potential new way of testing whether a mask fits that can be performed at home with materials costing approximately £20.</p>
<h2>Good fit isn’t universal</h2>
<p>Our <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0245688">first piece of research</a> measured how well different masks blocked ambient air particles from entering them when being worn. This involved taking continuous measurements of the concentration of air particles in the ambient air outside the mask as well as in the air inside the mask (via a valve connected to it) and then looking at differences between the two to see if air was seeping in.</p>
<p>This is what’s known as quantitative fit testing. It’s a commonly used and highly reliable way to test mask fit. The US Occupational Safety and Health Administration (OSHA) mandates that for an N95 or similar mask to be deemed suitable for use, it must score above 100 in <a href="https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.134">such a test</a>.</p>
<p>We ran quantitative fit testing with seven participants, who each tested five different types of N95 mask, as well as a KN95 mask and a surgical mask. Three participants also tested some fabric masks. This meant N95 masks were tested a total of 35 times; only in six instances did their scores exceed 100. When poorly fitting, we found the N95 masks provided not much more protection than the surgical or cloth masks. The KN95 masks also performed very poorly when they didn’t fit, offering no more protection than a cloth or surgical mask. </p>
<p>It therefore can’t be assumed that high-performance masks are universally highly protective. Proper fit is necessary for protection, and even the best performing mask, the 8511 N95, fit only three out of seven participants. Some N95 masks, such as the Aero Pro and Xiantao Zong, didn’t fit any of the participants adequately.</p>
<h2>Self-assessing fit often inaccurate</h2>
<p>Before measuring quantitative fit, we had also had the participants themselves assess whether they thought each mask fit (what’s known as qualitative fit testing). They did this by following <a href="https://www.wyccn.org/uploads/6/5/1/9/65199375/how_to_put_on_and_fit_check_an_ffp3_respirator_2013.pdf">NHS guidelines</a>: visually and manually inspecting the mask each time, carefully feeling around the edge for air leaks and adjusting the fit as necessary. We then had participants rate each mask on two criteria – whether they believed the mask fit and how confident they were in their decision. </p>
<p>We then compared these self-assessments with the highly reliable, quantitative fit data that we gathered. In the following graph, you can see how the actual and estimated fit of the five N95 masks compared across the seven participants. (There were four women and three men, aged between 18 and 74. They are listed on the X axis below.) </p>
<p>The height of the bars shows how well the masks fit – as mentioned previously, only six times did an N95 mask fit well enough to pass the OHSA’s 100-point benchmark. The colour of the bars shows what was predicted in each self-assessment: green means the participant thought it did fit, red that it didn’t, and the darker the colour the greater the confidence in their prediction.</p>
<p>If predicting fit accurately, bars above the 100-point mark are green and those below are red. So, as you can see, the participants weren’t particularly accurate in assessing the fit of the various N95 masks. They correctly identified masks that did fit, but regularly misidentified poorly fitting masks as being adequately able to protect them. There’s also no correlation between their confidence in their predictions and the predictions’ accuracy. </p>
<p>These findings suggested that the self-administered method of checking fit used in this study isn’t reliable and that an alternative is needed.</p>
<h2>How to improve self-assessment</h2>
<p>We then had a go at developing a <a href="https://www.cambridge.org/core/journals/disaster-medicine-and-public-health-preparedness/article/performing-qualitative-mask-fit-testing-without-a-commercial-kit-fit-testing-which-can-be-performed-at-home-and-at-work/41EDE04D0885104F2ECBF5725047D7C8">better method</a> of qualitative fit testing that could be performed at home for a reasonable price. </p>
<p>In healthcare settings, a different method is used to test high-filtration masks. Rather than assess fit visually and by touch, a substance with a certain taste is released into the air around the mask wearer. If they can taste the substance, it indicates the mask doesn’t fit properly. </p>
<p>This technique requires a suitable enclosure, as well as a flavoured test solution and a nebuliser to spray it into the air. These supplies can be expensive and, during COVID-19, difficult to obtain. So, we showed how to replicate this method at home using inexpensive alternatives purchased on Amazon for around £20. </p>
<p>An aroma diffuser can replace the nebuliser, and can be used to aerolise saccharin dissolved in water into an enclosed space. The participant then tests to make sure they can taste this without a mask on, and then sees if they can taste it with a mask donned. To ensure a thorough test, the user can move the diffuser around so that its vapour touches all edges of the mask, or they could cover their head with something – such as a densely woven towel – to help concentrate the mist around their face.</p>
<p>It’s important to note that while this method was shown to be effective in our study, it is not regulator-approved, and so should be used at one’s own risk. We do not certify its safety.</p><img src="https://counter.theconversation.com/content/155987/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Eugenia O’Kelly does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>When not properly fitted, high-filtration masks offer only a little bit more protection than cloth or surgical ones.Eugenia O’Kelly, PhD Candidate, Department of Engineering, University of CambridgeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1537782021-02-11T13:17:45Z2021-02-11T13:17:45ZCDC says masks must fit tightly – and two are better than one<figure><img src="https://images.theconversation.com/files/383631/original/file-20210210-21-19gan9d.jpg?ixlib=rb-1.1.0&rect=341%2C668%2C2809%2C2489&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Masks work only if they fit well, and wearing two can ensure a tight fit.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/woman-uses-a-double-mask-to-avoid-the-intense-smell-news-photo/1209513771?adppopup=true"> Eduardo Maquilón/Getty Images/Stringer via Getty Images News</a></span></figcaption></figure><p>On Feb. 10, the Centers for Disease Control and Prevention released <a href="https://www.cdc.gov/mmwr/volumes/70/wr/mm7007e1.htm">new mask guidelines</a> based on a study of how mask fit affects the wearer’s exposure to airborne particles. With <a href="https://doi.org/10.1038/d41586-021-00121-z">more transmissible COVID-19 strains emerging</a> around the world, it is important to properly use the <a href="https://doi.org/10.1073/pnas.2014564118">right kinds of face masks</a>.</p>
<p>Some practices – such as taking your mask off to speak or wearing your mask below your nose – are clearly problematic. Other mistakes may be less obvious. Everyone still needs to be wearing masks as much as possible – <a href="https://www.npr.org/sections/health-shots/2021/01/12/956051995/why-you-should-still-wear-a-mask-and-avoid-crowds-after-getting-the-covid-19-vac">even if you’ve been vaccinated</a> or have previously been infected with COVID–19. So how do you get the most out of a mask?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/383634/original/file-20210210-23-1npyuma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A table with multiple KN95 masks in packaging." src="https://images.theconversation.com/files/383634/original/file-20210210-23-1npyuma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/383634/original/file-20210210-23-1npyuma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/383634/original/file-20210210-23-1npyuma.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/383634/original/file-20210210-23-1npyuma.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/383634/original/file-20210210-23-1npyuma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/383634/original/file-20210210-23-1npyuma.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/383634/original/file-20210210-23-1npyuma.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">KN95 masks are good and widely available, but performance varies.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/VirusOutbreakFlorida/6b93e1ac00464b2395bd2f735f0f7e81/photo?Query=kn95&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=11&currentItemNo=1">AP Photo/Wilfredo Lee</a></span>
</figcaption>
</figure>
<h2>Mask materials</h2>
<p>Your mask material is the most important consideration. Certain manufacturing techniques can make masks more efficient at filtering out the tiny droplets and aerosols that can carry the coronavirus.</p>
<p>During the past year, my graduate students and I at Binghamton University teamed up with scientists from the surgical robot company <a href="https://www.intuitive.com/en-us">Intuitive Surgical</a> and the Intuitive Foundation to test the effectiveness of different fabrics at filtering out airborne particles. Our work has been <a href="https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/cloth-face-cover-guidance.html">used by the CDC to inform mask guidelines</a>.</p>
<p>Researchers believe that an infected person who talks expels droplets that can spread COVID-19 – especially in the <a href="https://doi.org/10.1016/j.jaerosci.2008.11.002">2- to 5-micron range</a>, about 10 times smaller than the width of a typical human hair. One reason to wear masks is to catch these relatively big particles before they dry out and shrink into <a href="https://theconversation.com/coronavirus-drifts-through-the-air-in-microscopic-droplets-heres-the-science-of-infectious-aerosols-136663">smaller particles, called aerosols</a>, which linger in the air longer because of their diminished size. </p>
<p>For example, a 3-micron saliva droplet could <a href="https://doi.org/10.1073/pnas.2006874117">shrink down to about 1 micron</a>. Researchers think that droplets in the 2- to 5-micron range <a href="https://doi.org/10.1073/pnas.2014564118">are most transmissive of COVID-19</a>. This range is the sweet spot for droplets to linger in the air due to their small size, while still having a high probability of containing the virus.</p>
<p>N95 masks are the gold standard among lightweight respirators and are at least 95% effective at filtering out <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7157953/">particles at 0.3 microns</a>, well below the average size thought to dominate COVID-19 transmission. They are typically greater than 99% effective for particles 2 to 5 microns across. When leakage around the mask seal is taken into account, <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4589166">the performance typically drops to 90% to 95%</a>. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/383638/original/file-20210210-17-qy6plm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Woman pinching nose of mask checking for good fit" src="https://images.theconversation.com/files/383638/original/file-20210210-17-qy6plm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/383638/original/file-20210210-17-qy6plm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/383638/original/file-20210210-17-qy6plm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/383638/original/file-20210210-17-qy6plm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/383638/original/file-20210210-17-qy6plm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/383638/original/file-20210210-17-qy6plm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/383638/original/file-20210210-17-qy6plm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A well-fitting mask won’t allow much air to leak around the seal to the face, especially around the nose, chin and facial hair.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/VirusOutbreakNewJerseyTesting/86d06f4157cc4cf3bcdd3f87c964888b/photo?Query=mask%20fit%20test&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=4&currentItemNo=0">AP Photo/Matt Rourke</a></span>
</figcaption>
</figure>
<p>KN95 masks, which have become more prevalent in the U.S. over the past few months, are the Chinese equivalent of N95 masks and are often the next best mask option in terms of performance. While KN95 masks often meet the N95 specifications, some researchers found their <a href="https://doi.org/10.1101/2020.07.25.20161968">performance to be inconsistent</a> in a study that has not yet been peer reviewed. The CDC maintains a list of <a href="https://www.cdc.gov/niosh/npptl/respirators/testing/NonNIOSHresults.html">internationally produced masks and their filtration performance</a> that you can use to confirm the performance of masks before purchase.</p>
<p>Medical-procedure masks – specifically <a href="https://www.astm.org/DATABASE.CART/HISTORICAL/F2100-19.htm">ASTM F2100-19, Class 1 masks</a>, the blue papery ones you see everywhere – are typically made of several layers of meltblown nonwoven fabrics. If one had a perfect seal to your face, the material could filter out <a href="https://doi.org/10.1520/F2299_F2299M-03R17">95% of particles as small as 0.1 microns</a> across. But these masks don’t seal all that well, and when you take into account the air leakage, <a href="https://doi.org/10.1017/dmp.2013.43">filtration in typical usage drops to about 80%</a>.</p>
<p>Cotton masks are among the most commonly worn and can also provide decent filtration. The filtration varies according to the tightness of the weave, and one study found that two layers of various widely available cotton fabrics filtered out between <a href="https://doi.org/10.1017/dmp.2013.43">34% and 66% of particles</a> in the 2- to 5-micron range. This is good for catching particles from a person talking, but it won’t block small aerosols in the environment. </p>
<p>In our research, we tested a wide range of fabrics to see which worked best. Some samples were washed as many as 10 times with a variety of detergents and then retested for effectiveness. In <a href="https://doi.org/10.31224/osf.io/nrtgb">our study</a>, which is currently under peer review, we found the best combination was soft flannel on the inside for comfort, thin-as-possible cotton on the outside and an efficient filter in the middle.</p>
<h2>Two masks are good, but make sure they fit</h2>
<p>No matter how good a mask’s material is, it won’t work well if it doesn’t fit well. A lot of filtration efficiency is lost from leakage around the face mask, such as around the bridge of the nose or at the gaps between any facial hair and the mask. A well-fitting mask is one that seals tightly onto your face, ensuring that almost all the air you breathe goes through the filtering material rather than through gaps in the sides. </p>
<p>The CDC’s new guidelines are based on a <a href="https://www.cdc.gov/mmwr/volumes/70/wr/mm7007e1.htm?s_cid=mm7007e1_w#F1_down">study that tested ways to improve how masks fit</a> – specifically double-masking and what they call “knotting and tucking.” </p>
<p>Double-masking is wearing a cotton mask over a medical-procedure mask. Knotting and tucking entails tying a knot in the elastic loops that go over your ears, close to where they attach to the mask. Then, you tuck the extra mask fabric into the gap that is often present where the ear loops attach to the mask, and flatten that part as much as possible. Both of these tricks to make a better fit decrease the mask-wearers’ <a href="https://www.cdc.gov/mmwr/volumes/70/wr/mm7007e1.htm?s_cid=mm7007e1_w">exposure to potentially infectious aerosols by 95%</a> as compared with wearing no mask at all. That’s a 15% improvement over the <a href="https://doi.org/10.1017/dmp.2013.43">80% efficiency</a> found when using a single surgical mask. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/383637/original/file-20210210-19-121ymrx.gif?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="(a) Single mask with a gap, (b) double mask and (c) knotting and tucking on mannequins." src="https://images.theconversation.com/files/383637/original/file-20210210-19-121ymrx.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/383637/original/file-20210210-19-121ymrx.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=173&fit=crop&dpr=1 600w, https://images.theconversation.com/files/383637/original/file-20210210-19-121ymrx.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=173&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/383637/original/file-20210210-19-121ymrx.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=173&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/383637/original/file-20210210-19-121ymrx.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=217&fit=crop&dpr=1 754w, https://images.theconversation.com/files/383637/original/file-20210210-19-121ymrx.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=217&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/383637/original/file-20210210-19-121ymrx.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=217&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Gaps on the sides of single surgical masks (a) can be reduced by (b) using a lightweight cotton mask to create a closer fit to the face or (c) knotting and tucking.</span>
<span class="attribution"><a class="source" href="https://www.cdc.gov/mmwr/volumes/70/wr/mm7007e1.htm?s_cid=mm7007e1_w#F1_down">CDC</a></span>
</figcaption>
</figure>
<h2>DIY fit test</h2>
<p>To get the best fit when using a mask, bend the metal nosepiece so that the mask tightly fits the curve of your nose. It is also important to make sure your mask fits beneath your chin and to remove any facial hair – air will take the path of least resistance through stubble rather than through the fine fibers of the mask.</p>
<p>Some places, such as hospitals and labs, do mask fit tests that are certified by the Occupational Safety and Health Administration, but these are impractical for home use. You can do your own qualitative fit test at home by lighting <a href="https://doi.org/10.1007/s11869-009-0061-z">a citronella or other oil-scented candle</a> and trying to smell it with and without a mask. The aerosols from a <a href="https://doi.org/10.1080/02786820600612250">citronella candle are 0.01 to 0.02 microns across</a> – much smaller than typical droplets from humans that would contain COVID-19. If you can’t <a href="https://doi.org/10.1002/alr.22682">smell the candle</a>, or the smell is significantly reduced, you’re likely wearing your mask correctly.</p>
<p>Keep in mind, however, that this test is far from exact. For instance, cotton masks won’t filter out these tiny candle aerosols, but are still an important tool to block the majority of coronavirus droplets.</p>
<p>Making sure you are getting the most out of your masks is critical to slowing this pandemic. Double-masking or knotting and tucking, as well as using the right materials, can ensure that you and those around you are safer.</p>
<p>[<em>Get our best science, health and technology stories.</em> <a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-best">Sign up for The Conversation’s science newsletter</a>.]</p><img src="https://counter.theconversation.com/content/153778/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Scott Schiffres received grant funding from Intuitive Foundation and Cardinal Health relating to mask research. </span></em></p>How well your mask works depends on how well it fits. Wearing two snug masks made of different materials offers 95% protection from exposure to aerosols that could contain the coronavirus.Scott N. Schiffres, Assistant Professor of Mechanical Engineering, Binghamton University, State University of New YorkLicensed as Creative Commons – attribution, no derivatives.