There is a small piece of film on the police mask. What is that?

You mean the breathing valve, right? When inhaling, the film will block the invasion of harmful substances, and when exhaling, the film will open, so that the wearer will not feel suffocated just now. Wearing a mask is a good habit, which can prevent harmful substances such as particles and droplets from entering the body and affecting people around you when you are sick. It's just that many of us are lazy, or most masks are uncomfortable and unsightly, so we don't want to wear them. In economically developed and densely populated areas such as Hong Kong and Japan, wearing white masks has long been commonplace and even developed into a culture. Don't feel that someone is not used to looking at you differently. There are more and more people wearing masks around us. It will be fine after a long time. If you are still worried about this, you can start with a pure white mask. Stars wear simple and generous white masks, just like a fashion. Recommend JD, an advanced medical mask imported from the United States, which is not only simple in appearance, but also powerful in protection. Don't worry about being abrupt, and you can prevent allergies with peace of mind.