At the start of the COVID-19 pandemic we did not know much about which/if face masks were effective at preventing the spread of the virus. In fact some researchers even suggested that cloth face masks may do more harm than good because they would result in people touching their faces more often. However, as scientists continue to study COVID-19 at unprecedented rate more and more data have started to point to the fact that cloth face masks can be effective. Since countries all over the world are starting to see signs of a second wave of the virus and in other places the first wave never ended - it seems like face masks aren’t going anywhere anytime soon. So having a few reusable/effective cloth face masks will prevent a lot of single wear masks from ending up in landfills as well as save you a lot of money. This post won’t focus on why face masks can help slow the spread of the virus - you can read more about that here. Instead we’re going to update you on what the science says about which type of cloth face masks can keep you and your loved ones the safest.
What does it mean for a mask to be "effective"?
The most recent study that aimed to answer this question tested several types of fabrics as well as N95 and single use surgical masks by measuring how good they were at filtering small particles (Konda et al 2020). When we say small, we mean really really small particles - 10 nanometers to 6 micrometers. Just to help visualize this, the SARS-CoV-2 virus has a diameter around 100 nanometers (Bar-On et al 2020), and a sheet of paper is about 100 thousand nanometers thick (www.nano.gov).
When people breathe they exhale extremely small particles in the form of aerosols and it seems like SARS-CoV-2 may be transmittable through these tiny droplets (Droegemeier et al 2020). The size of aerosols generated when we breathe varies and affects how they can be filtered as well as how they behave when they are in the air. Think about an acorn falling from a tree versus pollen floating through the air - the former will hit the ground quickly and would be easy to see and catch while the latter could travel through the air for a while and would be much harder to catch. Because of this variation, cloth face masks should be able to stop/filter various sizes of aerosol particles to be effective. The recommendations in the following paragraphs are based on the latest scientific results on how well each fabric filters aerosols of different sizes.
...cloth face masks should be able to stop/filter various sizes of aerosol particles to be effective.
Which kind of fabric makes the best mask?
The results from this study showed that materials with a tight weave and low porosity were the best kind of fabric to use to make a face mask. Masks made from two types of fabric - high thread count cotton and either silk, chiffon, or flannel were the best at filtering multiple sizes of particles. While masks made with a single layer of low thread count cotton - like the kind they make a lot of t-shirts from, and those made from flannel were the least effective at filtering aerosols. The researchers who led this study also pointed out that improperly fitted masks are much less effective - no matter what they are made of.
The researchers who led this study also pointed out that improperly fitted masks are much less effective - no matter what they are made of.
According to this study, if you’re going to make cloth masks it’s better to use multiple layers of any fabric and it’s best to use two kinds of fabric such as high thread count cotton and silk.
Fabrics ranked by ability to filter particle >300 nanometers (when worn correctly).
How to make face masks and what are the guidelines for properly wearing a mask?
Masks are STILL super important, by wearing them you are keeping yourself and others safe. When you wear a cloth mask you are also keeping the environment safe. Here are a few links with patterns for making cloth face masks:
Remember a poorly fitted mask is just making you uncomfortable, and not really keeping anyone safe. In order to help you know if your mask fits correctly and give you a few tips on how to maintain your mask we included an infographic from the world health organization (WHO).
In conclusion, wear your mask, wash your hands, and stay safe out there!
Works Cited
Konda et al. Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks. ACS Nano. 2020 Apr
Bar-On et al. SARS-CoV-2 (COVID-19) by the numbers. eLife. 2020 March
Droegemeier et al. Rapid Expert Consultation on the Possibility of Bioaerosol Spread of SARS-CoV-2 for the COVID-19 Pandemic. Apr 2020
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