May 7, 2020

Heating could be best way to reprocess N95 respirators

Editor's Note

This study from Stanford University tests five methods for disinfecting N95 masks and finds that heating them preserves their filtration efficiency for 50 cycles of disinfection.

In the study, instead of analyzing N95 masks, which were needed by healthcare workers, the researchers examined pieces of the fabric used to make the masks.

The researchers found that:

  • Spraying the fabric with an ethanol or chlorine bleach solution drastically reduced the filtration efficiency after only one treatment, from 96% to 56% (ethanol) or 73% (bleach).
  • One steam treatment maintained filtration, but five steam treatments led to a sharp decline in efficiency.
  • UV radiation allowed up to 20 cycles of disinfection, but administering the exact dose of UV that kills the virus without damaging the mask fabric could be a problem.
  • Heating at 185 F for 20 minutes allowed the fabric to be treated 50 times without loss of filtration efficiency.

Also, the researchers say, frequent donning and removing of N95 masks could affect fit, which also affects performance.

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