In practice N95 masks worn for a long time have been used, you can insist on using 1-2 days of time, but during the epidemic used disposable N95 masks, it is recommended that after using once do not use again, so in the isolation ward of the epidemic area doctors and nurses wearing protective clothing used N95 masks such as in the case of a 6-hour or 4-hour shift, N95 masks used only once will be discarded and disposed of as medical waste. N95 masks have an efficiency of over 95% in blocking particles >0.3μm. The reason for discarding after a period of use is that in infected areas or wards, other parts of the mask may come into contact with viruses or the inside of the mask may block infectious viruses, so it is recommended that they be discarded after a single use. Isolation gowns worn by frontline doctors and nurses generally do not need to be changed for 6 hours, and may need to be discarded and disposed of after 6 hours. Content source: Dr. You Lai