Author | Comment | Last activity | Moderation | ||
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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 » | almost 5 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 » | almost 5 years ago |