At a time when masks are in short supply, they can be reused if they are clean and structurally intact, especially if the inner layer is not contaminated, and how they are used depends on the occasion on which they are worn. General residents use disposable masks in less risky places, and ordinary medical masks for access to crowded public places. After each use it should be placed in a clean, dry and ventilated place. You can put the mask in a clean paper bag or put a clean sheet of paper on top of it on the table and fold the mask inward to avoid getting dirty. If the mask is wet, dirty, deformed, damaged or smelly, it needs to be replaced in time.