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 largely unreliable as they do not prevent infectious diseases. 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.