Wearing two masks does not work as well as wearing one. Some people like to wear two masks, wearing a surgical mask inside and an N95 mask outside, thinking that the effect will be better. In fact, this is not the case, because wearing two masks, the surgical mask in the inner layer will affect the airtightness of the mask, thus not being able to make the gas discharge smoothly and cause chest tightness. If you wear two masks there may be a waste of resources and will not play a good role in protection, and at the same time there will be a certain impact on the nasal mucosa. So if you want to do a good job of protection, a simple surgical mask or N95 mask is enough to use, one will do.