Author Comment Last activity Moderation
BostonFern "I also wonder about the material in a HEPA filter. It's supposed to be even more efficient than a surgical mask. But I don't know how breathable ..." | Read more » about 4 years ago
BostonFern "I've learned a few more things from my online activities. It was paper towel that the Hong Kong University found to be effective. They took diffe..." | Read more » about 4 years ago