COVID-19 news you can use

How you can reuse N95 masks. It’s a very technical paper but the takeaways I got from it are:

  • The N95 mask gets most of its filtration capability from semi-permanently electrically charged particles in the mask material.
  • Attempting to clean the masks with alcohol or even alcohol vaper will SERIOUSLY degrade the filtration ability of the mask. Don’t do that!
  • “…it is reported (if it is true) that COVID-19 cannot survive at 65C for 30 minutes. Therefore, it is safe to treat the masks in hot air at 70C for 30 minutes and this process can be repeated multiple times to reuse the masks without a noticeable loss of efficiency. But be sure to suspend the masks in the hot air in the oven without contacting or putting the masks too close to a metal surface. The respirator can be hung in the oven using a wood or a plastic clip on its edge of non-breathing zone or put on a wood grill at least 6” away from a metal surface.”
  • “…our investigation showed that the charge loss on the electret is unnoticeable by sterilization using 125oC steam for three minutes.”
  • “…our investigation showed that the charge loss on the media is unnoticeable in boiling water for three minutes but stirring on the mask is not recommended to avoid its physical damage.”
  • If you plan to use water to sterilize the mask “…be sure that the inner or the outer veil of the mask is not made of paper-like tissues – paper pulp or nonwovens bond by water soluble binder, which will either dissolve in water resulting in loose fibers in the veil or the loss of its strength after exposing to water.”

To save you a minute or so of your time, 70C is 158F and 125C is 257F.


4 thoughts on “COVID-19 news you can use

  1. i’ve wondered about microwaving them; if the virus has enough internal moisture to actually heat up and sterilize it.

  2. Research shows that as little as 5 seconds in a standard microwave can render the coronavirus inert. Other types may require longer…up to two minutes. As long as whatever you are trying to sterilize is microwave safe it’s not a bad method to use and MUCH less destructive to fiber masks than many methods…as long as there is ZERO metal in the mask construction.

    • Any RF engineers out there? I believe metal is ok as long as its longest dimension is less than one wavelength at microwave frequencies, i.e., about the length of a clinched staple. That was the explanation given by non-RF-guy Alton Brown when he was using staples to close a paper bag while making popcorn in a microwave oven.

  3. I saw elsewhere that 65C kills the virus, 70C is just adding a safety buffer. If you have a food dehydrator, it’s likely the top setting on it is 65C. That’s my plan.

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