In a recent interview with Curious City reporter Monica Eng on WBEZ Chicago, Natasha Mubeen Chida, MD, assistant professor of medicine at Johns Hopkins Medicine, described a simple “candle” trick for testing the efficacy of your mask in just one blow. “One good test is if you’re wearing your mask and you try to blow out a candle. If you cannot blow that candle out, your mask is doing a pretty good job of preventing air from your mouth from getting out,” said Dr. Chida. (I’ll just wait here while you go ahead and give it a try for yourself.)
“The goal is not to protect yourself, the goal is to protect people around you.” —Natasha Mubeen Chida, MD
This trick works because the primary purpose of wearing a mask is to decrease your chances of transmitting the virus to other people. “The goal is not to protect yourself, the goal is to protect people around you. These kinds of masks are most effective at preventing you from transmitting something to someone else,” says Dr. Chida. However, as Marcus Plescia, MD, MPH, chief medical officer of the Association of State and Territorial Health Officials, points out, it’s not necessarily a foolproof way of testing your mask. “If you have an N95 and a surgical mask I would try it out with those. My sense is that you could blow out a candle with a surgical mask,” he says. And yet, we do know that those masks are very effective at blocking the route of COVID-19.
In laboratory settings, Dr. Plescia says doctors have a more sophisticated way of saying yay or nay to a particular mask. “The ‘gold standard’ is how we test mask fit on masks used for airborne precautions. For those, we spray the wearer with a saccharine spray. If you taste the saccharin inside the mask, then the fit is not adequate,” he says. Since saccharin—a type of artificial sweetener—is somewhat expensive and hard to come by, though, the candle blowing trick will work just fine for now. “I think most cloth masks that have two layers of fabric will provide reasonably good protection,” says Dr. Plescia. “And don’t forget that eye protection is important, too. I recommend people wear glasses when they are out or face shields if you want to be extra cautious.”
Just remember, wearing your mask doesn’t negate the importance of social distancing. Even if the flame of your cinnamon bun candle doesn’t budge when you blow, honor the six feet between yourself and others.
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