Under what circumstances can I not wear a mask? 
If you are alone and not in close contact with outsiders, you don't need to wear a mask. For example, there are no suspected patients at your home, no close contacts, family members who have returned from the epidemic area. You didn't take guests, suspected or confirmed patients in the affected area for a ride. It is not necessary to wear a mask in an outdoor ventilated place by yourself. For example, you take a walk in the community and parks and on streets with few pedestrians. If you work in the open air with good ventilation and keep a proper distance from nearby people, wearing a mask is not required. Measures of disinfection, temperature measurement, and ventilation are strictly adopted in the office and there are no suspects or close contacts among your colleagues, then you don't need to wear a mask.
 
Can I not wear a mask at low risk areas?
A low risk area does not mean that there is no risk. Some areas have just been adjusted from high risk and medium risk to low risk. Residents must usually take personal protection and reduce unnecessary gathering. It is recommended that everyone should wear a mask when going to crowded places and monitor your health by yourself.
 
How to reuse a mask?
Except for people with high exposure risks, masks worn by healthy people can be used repeatedly. You can appropriately exdend the time and frequency of use. Generally speaking, if the mask is not stained or deformed obviously, it is not necessary to change it every four hours. Masks that need to be used again can be hung on the clean, dry and ventilated place, or put them in a clean, ventilated paper bag. The mask should be stored separately to avoid contact with each other. If the mask is dirty, deformed, damaged or smelly, it needs to be replaced in time.
 
These are all wrong!
Spray the mask with alcohol and disinfectant, which will reduce the protection efficiency. It is not recommended that you use it again. Heating the mask with a microwave oven, electric oven or steamer will damage the internal structure of the mask and reduce the protection efficiency. It is not recommended that you should use it again.
 
Do not wash your hands before wearing or taking off the mask.
The hands will touch the outer layer of the mask, bringing the possibility of contact transmission.
 
Confirmed or suspected patients wear masks with breathing valves. The exhalation valve of the mask is a one-way valve. When exhaling, the positive pressure of the discharged air makes the valve open, and the exhaled air is quickly discharged. There is no filter layer during the exhaling process. The patient may discharge the virus.
 
Infants wear masks.
Infants and very young children shouldn't wear masks, which can easily cause suffocation.
 
Wear more than one mask.
Wearing more than one mask cannot increase safety.