Disposable masks, such as medical masks, disposable surgical masks, N95 masks, etc., cannot be used again after being scalded with boiling water, and gauze masks can be scalded with boiling water and used again. Because disposable masks, such as medical masks, disposable surgical masks, N95 masks, etc. have a waterproof layer and a filter layer, which can prevent both liquid splashing and the passage of non-oil particles. Once wetted by respiratory water vapor, the protection will be reduced. After boiling water scalding, the waterproof layer is completely destroyed and the filtering effect also decreases, so it cannot be used again. However, gauze masks can be recycled, as they are not waterproof and do not prevent infection from new coronavirus pneumonia. To prevent new coronavirus, disposable surgical masks and N95 masks can be used, but care needs to be taken to replace them in a timely manner, usually once every 4-24 hours. If there is more water vapor on it, the protective effect will be reduced, and it should be replaced as early as possible.