Understanding Mask Effectiveness: A Physics-Based Guide to COVID-19 Protection

Physics don't often have a lot to do with personal finance, but in this case, knowing a little about fluid dynamics can keep you from wasting your money. Turning physics into a public health intervention on top of that is just a triumph of science — even if it's combatting a failure in marketing and design.

You've probably become something of an expert in mask-wearing since the COVID-19 pandemic began in earnest where you live. Masks have been proven to dramatically reduce transmission of the coronavirus, and they're one of the best ways to both tamp down the spread of the disease and enable us to live anything resembling a normal life for the duration. It's no surprise, then, that tons and tons of different kinds of masks have sprung up on the market. Some are simple, disposable, or washable, while others are hilariously overengineered. (We've already had a discussion about Halloween masks; they don't work.) One type in particular, however, is about as much good as not wearing a mask at all.

Researchers with the federal government's National Institute of Standards and Technology have just released a very convincing video showing why you should avoid any mask that includes a ventilation hole in the surface. A side-by-side comparison shows that a regular N95 mask, the gold standard in filtration, keeps what you breathe out pretty well reined in, while a mask with ventilation shoots out your exhalation in a concentrated stream, which fully defeats the purpose. Watch the 30-second video for yourself — and stick with fully covering your face, with no fancy workarounds.