How often and what conditons should a mask be replaced?

Generally, the wearing time of disposable medical masks and medical surgical mask is limited , the cumulative wearing time should not exceed 8 hours. The mask used by occupational exposure persons should be not more than 4 hours and cannot be reused.  Overtime wearing will extremly reduce the protective performance of the mask . 

The face mask should be aslo replaced in time when the following conditions got , 

1. When the mask is wet;

2. When there is peculiar smell in the mask;

3. When the respiratory resistance increased obviously;

4. When the mask is damaged;

5. When the mask cannot be tightly fitted with face

6. When the mask is contaminated (for example, when it is stained by foreign objects, such as blood stains or droplets);

7. When the mask has been used in an isolation ward or in contact with a patient.