Interesting, I did not know this. I'm now curious! https://www.nature.com/articles/d41586-020-02550-8 https://www.nature.com/articles/d41586-020-02550-8 is a b

Interesting, I did not know this. I'm now curious! https://www.nature.com/articles/d41586-020-02550-8 https://www.nature.com/articles/d41586-020-02550-8 is a brief Nature post from Peter Tsai, who invented this electrostatic filter. In it he says that the charge are "permanent," and adds: > They wanted to sterilize the masks for reuse without damaging them or destroying the electrostatic charge. I knew that heat would not alter the charge, but that alcohol would erase it. The N95DECON project says that masks can be reused if stored at room temperature and do not lose efficiency: https://www.n95decon.org/publications#time https://www.n95decon.org/publications#time I see some studies that find that various decontamination methods (high heat, various disinfectants) can cause the charge to dissipate, e.g., https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7724761/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7724761/ - but I'm not advocating doing any of those, I'm just advocating leaving it hanging on a hook by your door when you get home. And, interestingly, those studies show that while filtration may drop below 95%, it's still pretty high, so I think that yes, a discharged N95 is still more effective than a cloth mask. But it'd be good to find a direct study. I'm having trouble finding a source that says the filtration performance drops after a day. I did find something that says that the N95 standard requires it must keep working for at least 24 hours, but that's the other direction. (And, anecdotally... the masks I ordered are shipped stacked together, not individually wrapped, in a cardboard box. They've presumably been in the box for a while at the warehouse. While it's true that cardboard is an insulator, so is air, and I'm not sure that the mask hanging by my door is losing charge any faster than the mask sitting in the box.) One thing that does seem to be true is that getting the mask wet can cause the charge to dissipate. If I'm wearing my mask in humid conditions and biking (I usually leave my mask on if I'm stopping frequently), I'll notice that it gets damp, and I do change it when that happens. If your home is extraordinarily humid, maybe put your mask in a brown paper bag or something.