Disposable masks usually have two sides, generally divided into darker or lighter sides. The lighter side should be the face contact surface and the darker side the outside. You can also judge the front and back of the white mask according to the position of the metal strip. 

The metal strip is above and outside should be the correct way to wear it. At this time, the side where the metal strip is located is outside. When wearing a mask, the metal strip should be pressed until it is close to the face. Generally, the blue side is outward, the blue side is smooth, the white side is rough, the rough side is usually the inside, and the smooth side is the outside. Because the inner layer is designed to be lighter in color and not stained, it is safer for the respiratory system, while the outer layer is darker and relatively resistant to dirt. When wearing a mask, you must pay attention to the pros and cons, you can't wear it wrong, otherwise the effect of the mask will be greatly reduced.