Letter Re: Microwave Oven Method for Decontaminating N95 Face Masks


Dear JWR:
I had an interesting conversation with a member of the CDC about decontaminating N95 face masks. The study results can be found here.

You’ll notice that the test gives positive results but more research is needed. Here was the conversation I had with Edward Fisher after reading it.

Here are some snippets from our exchange:

1. Did you remove the metal nosepieces from the masks before sterilization?
2. Any updates to this study?

We did not modify any of the tested filtering facepiece respirators
before decontamination. If the masks had metal nosepieces, they were
not removed.
There are no further updates on the study. Currently my lab is
focusing on evaluating the risks associated from handling and/or
reusing previously worn masks.

OK thanks! I thought perhaps they were removed because of the metal in
a microwave. Did you have metal arcing from the metal nosepieces?

We did not experience arcing from the metal nosepieces. The key to
the microwave method is the addition of water. Without water and
steam, the microwave can melt the masks. (See Viscusi et al. Ann.
Occup. Hyg., Vol. 53, No. 8, pp. 815-827, 2009). It should be noted
that the steambags have not been evaluated using Influenza and more
research is required. Currently, decontamination of disposable FFRs
is not recommended. As mentioned previously, we are now trying to
evaluate the hazards associated with handling and reusing contaminated
masks and have moved away from decontamination testing. This
may be helpful for any information you may be seeking
in regards to respirator research and influenza.

Keep an eye on this topic. If it’s effective it’ll really save on N95 mask costs. I think I’ll chance it if we have a pandemic and I’m wearing a mask but am not around anyone confirmed to be sick. – C.D.V.

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