In the absence of medical grade personal protective equipment (PPE), many of us have turned to homemade cloth masks to help stop the spread of coronavirus. But increasingly, research has shown that not all masks are created equal, and some are downright ineffective. A new video case study produced by Australian researchers shows that in order for a homemade cloth mask to stop viral transmission, it needs to have at least two layers of fabric. In effect, if your mask has just one layer of fabric, you can safely bet that it simply doesn’t work.
Using an LED lighting system and a high-speed camera, the research team filmed the dispersal of aerosols produced by a subject while speaking, coughing, and sneezing. The subject reflected the behavior of a healthy individual with no respiratory disease, meaning the coughs and sneezes used “normal,” everyday force that an asymptomatic COVID patient might produce.
Upon reviewing the footage, the team ranked the efficacy of the three cloth masks (as well as a three-ply surgical face mask, which was determined to be the most effective option). Overall, the correlation between the number of fabric layers and efficacy was stark: the more layers a cloth mask had, the more effective it was in protecting against the spread of droplets. The footage revealed that single-layer masks barely impeded the spread of droplets at all: in that demonstration, the aerosols dispersed through the air with visible ease.
The team noted that style of sewing also had an effect on the outcome. Masks that were sewn according to standards provided by the Centers for Disease Control (CDC) were far more effective than single-ply masks made with cotton t-shirts and hair ties.
So, the next time you head outside, make sure your DIY mask is up to the task. Opt for a design that includes a minimum of two layers of fabric (ideally three!) that’s been sewn based on the CDC’s standards. And for more on whether your mask is keeping you safe, Watch Bill Nye Test Which Face Masks Work the Best.