10pcs face mask reusable pm2.5 filter mouth masks with breathing valve bacteria proof flu protect black kf94 respirator

1. kf94 belongs to the korean standard, which means that the filter has a filtration rate of more than 94% for particles with an average diameter of 0.4 microns, and the use time of kf94 masks is up to 48 hours. 2. there is no fixed replacement time for kf94 masks. different environmental dust concentrations are different. the use time of each person is different. the dust holding capacity of various masks is different. 3. if you dont go to crowds or go directly to the flu, you can use the...