Based on advice from Dr. Peter Tsai, the inventor of the major filtering component in the impossible-to-obtain N95 masks, the following is a guideline for reusing masks of any type… N95, surgical, or DIY:
Leave your mask in dry atmosphere air for 3-4 days to dry it out. COVID-19 needs a host to survive–it can survive on a metal surface for up to 48 hours, on plastic for 72 hours, and on cardboard for 24 hours. When the respirator is dry in 3-4 days, the virus will not have survived.
So… first method for reusing masks:
Take 4 masks, and number them (#1-4).
On day 1, use mask #1, then let it dry it out for 3-4 days.
On day 2, use mask #2, then let it dry out for 3-4 days.
Same for day 3, and day 4…
MASK REUSE METHOD #2
You can also sterilize the N95 mask by hanging it in the oven (without contacting metal) at 70C (158F) for 30 minutes-it is reported that COVID-19 cannot survive at 65C (149F) for 30 minutes. If you’re not sure about how accurate your oven temperature is, use a small oven thermometer. Amazon: https://amzn.to/2Jygg8t
Use a wood clip to hang the respirator in the kitchen oven to do the sterilization.