N95/KN95 masks are more durable than surgical and other disposable masks, allowing them to be used for up to 40 hours, if properly cared for.
Many sources, including healthcare workers, have stated that they use a rotation method, where they have about 4-5 masks in constant rotation. When an N95/KN95 mask is not in use, they place the mask in a paper bag and allow it to dry out over the course of a few days. Recent tests show that the virus can remain active in an N95/KN95 for up to 72 hours, and the paper bag keeps the mask in a clean, isolated space, allowing it to effectively dry out and decontaminate. Ensure to write the date on the paper bag so that you are aware of how much time has passed between each use.
Using this method, if you were to take four (4) N95/KN95 masks and alternate them every three (3) days, your masks could last up to twenty (20) days.
When practicing this method, before donning your N95/KN95, ensure that it has not lost its shape, is visibly soiled or wet or shows general signs of wear and tear.
It's time to dispose of your mask and reach for a new one when:
It is worn in a high-risk setting
It is torn, the straps are broken or have lost elasticity
The fit loosens or shape is lost (i.e., collapsed cup, gaping)
Becomes visibly soiled (including makeup)
If it becomes wet from rain, snow, water or other external elements (condensation is okay, as long as it has been dried using the method discussed above)
KN95 / N95 masks are constructed to fit to the contours of the wearer’s face, especially if the mask is attached to the back of the neck and crown, and filter 95% of aerosols. Infection takes as long as 25 hours.