How to effectively wear masks? When is it not necessary to wear a mask?

Wearing masks in the right way can prevent the infection of respiratory diseases such as COVID-19 and influenza, which is good for both self-protection and public health.

The Joint Mechanism of the State Council on prevention and control of COVID-19 released a circular (No. 33, 2020) on printing and issuing the guideline promoting public health by wearing mask effectively amid epidemic. According to the guideline, there are four categories——general public, people at specific areas, key population groups and people with occupational exposure to effectively wear masks at different times as follows:  
 
General Public  
1, People stay at home, outdoors and other well-ventilated places with no crowds.
Protection suggestion: Not necessary to wear a mask.
 
2, People stay in crowded places such as offices, shopping malls, restaurants, meeting rooms, workshops, elevators and public transport.   
Protection suggestion: Carry along masks (disposable medical masks or surgical masks) in medium-risk and low-risk areas and wear masks in contact with others at the distance of less than 1 meter. Wear disposable medical masks in high-risk area. 
 
3, People have cold symptoms such as coughing or sneezing.
Protection suggestion: Wear disposable medical or surgical masks. 
 
4, People live with personnel in quarantine or that have recovered from the novel coronavirus and been discharged from the hospital.
Protection suggestion: Wear disposable medical or surgical masks.