The first factor to consider is the fit of the mask to the face. If there is a gap between the mask and the face to allow suspended particles to enter, then the mask becomes useless. Xi Ruizhi said that some of the masks sold in 7-11 convenience stores in China are not easy to use. Take the Green Shield mask, for example. This mask, which claims to have an efficacy of up to 99%, is actually put in its cotton mask A tiny filter element. Many masks on the market are made of cotton, which can form a large gap when worn, and cannot fit the face effectively. Whats more worrying is that many people walk around boldly and confidently after wearing this mask. If you wear glasses, a good way to check the fit is to see if there is fog on the lenses. If so, it means that the fit of the mask is not good.

Secondly, the material of the mask determines the ability of the mask to filter suspended particles. The National Institute for Occupational Safety and Health evaluates masks based on the total amount of particles filtered by each mask. For example, a N95 mask can filter out 95% of suspended particles in the air.

Whether a mask can breathe well is especially important for those who want to be outdoors. Some masks can be separated from the face when worn, thereby ensuring that the user can breathe smoothly, while some masks will force people to breathe harder and make people feel dull.