Little Difference Between DIY, Medical-grade Masks

Good news. Those homemade face masks work — and they might even be more breathable than medical masks, a recent study shows. The findings were published in the journal Extreme Mechanics Letters.

With the supply of professional and medical face masks limited, the Centers for Disease Control and Prevention (CDC) has recommended that people make their own cloth face coverings to help slow the spread of COVID-19.

Multiple studies have already established that household fabrics can help block tiny aerosol particles, but coughing, sneezing and speaking create larger droplets. However, masks must be comfortable and allow for easy breathing in order for them to be worn consistently, the researchers noted. “A mask made out of a low-breathability fabric is not only uncomfortable, but can also result in leakage as the exhaled air is forced out around contours of a face, defeating the purpose of the mask and providing a false sense of protection,” said co-author Taher Saif, PhD, in a press release. “Our goal is to show that many common fabrics exploit the trade-off between breathability and efficiency of blocking droplets — large and small.” Dr. Saif is a mechanical science and engineering professor at the University of Illinois, Urbana-Champaign.

There is no agreed-upon definition that differentiates “aerosols” from “droplets.” Previous studies on cloth masks have mostly focused on the filtration efficiency of household fabrics against aerosol particles between 10 nanometers and 10 micrometers in diameter. That is really small: Consider that there are 1 million nanometers and 1,000 micrometers in just one millimeter. (And a millimeter is itself one thousandth of a meter.)

11 common household fabrics

The researchers looked at how 11 common household fabrics worked as a barrier, compared to a commercial medical mask.

The fabrics tested varied between new and used, 100% cotton, cotton blends and synthetics. They were tested in single layers and doubled and tripled up. All of these fabrics were found to be considerably effective at blocking high-velocity droplets, even as a single layer. They also found 2 layers of highly permeable fabric, such as a T-shirt, can block droplets up to 94% as well as medical masks, while being about twice as breathable.

But don’t rely on the fabric alone

The researchers stressed, however, that the performance of a cloth face mask also depends on how it is worn and how much air can leak through the gaps. Masks should fit snugly over your mouth and nose, and be secured under the chin. Elastics or ties are personal preference, but should be fastened properly.

How you handle your mask is also important. Wash your hands before putting it on, and hold it by the ties or elastics. When removing it, avoid touching the fabric, only handling the ties or elastics.

Finally, washing your masks properly and frequently is essential. The researchers determined that household fabrics are more “water-soaking” than medical-grade masks. That means that virus droplets can soak into a homemade face mask and stay there for a longer period of time. Therefore, they must be washed frequently in order to decontaminate them. 

Making masks

Social media is showing many people have started making masks at home for themselves and for others. But they’re not hard to make if you’ve got a needle, thread and fabric. Many institutions have published guides on how to cut and sew your own homemade face masks, including the CDC, Johns Hopkins University and Vanderbilt University.

And there may be another benefit to using masks made at home. The researchers’ findings suggested that masks made from washable materials, such as cotton, help mitigate the environmental impact of single-use, non-biodegradable masks.

Sydney Shaw is an award-winning writer, editor and digital producer. She lives in New Jersey with her cat, Oliver.

 

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