Mask thickness does not equate to protection effectiveness. Medical surgical masks are relatively thin to the touch, but the filtration efficiency is high – the three layers of water-blocking layer, filter layer, and moisture-absorbing layer can effectively block virus invasion. The general cotton masks on the market, on the other hand, are thick, but basically do not have a role in preventing infectious diseases and are not reliable. In addition, the general public does not need to wear multi-layer masks to prevent it from causing poor breathing and suffocating, it is recommended to choose N95/KN95 or general surgical masks, and one layer is enough, the protection effect of other masks is not as good as these three.