FastCompany: “…Dan Formosa, a designer with extensive experience in creating medical masks, explains that this is a common problem in mask design. Every time you take a breath, you let out half a liter of air into the atmosphere. Very few masks—even professionally designed ones—create a perfect seal around the face. When there are gaps on the bridge of the nose and upper cheeks, this hot air comes out of your nose and mouth, fogging up the glasses. Formosa says that DIY masks, made with things like bandanas or T-shirts, make it even harder to prevent air from escaping upward. “It’s very hard to create a flat seal around the nose area, in particular, because the physiology of people’s noses varies so widely,” he says.

This fogging is annoying, but it could also be dangerous. It often prompts the wearer to touch his or her face to adjust or wipe their glasses, which could increase the risk of transmitting the virus from the fingers to the face. This would be completely counterproductive to wearing a mask in the first place. But don’t despair. There are several things you can do to decrease the amount of fog you create on your glasses. None of these solutions are perfect, and each comes with a trade-off. But they will help you through the next few months…”