When choosing a standard mask, if it is a temporary outdoor work, you can choose ordinary cotton masks to keep warm. If the air pollution is serious, such as haze and other weather, you need to choose PM2.5 masks, such as N95 disposable mask, which can be used for disease protection. Medical protective masks can play a certain role in preventing influenza. Ordinary disposable dust mask can prevent some dust, but the effect is average and cannot prevent diseases.