"Still, during periods of shortages ... when other preferred alternative respirators ... are not available, filtering facepiece respirator decontamination and reuse may need to be considered as a crisis capacity strategy," the OSHA guidelines say.
NIOSH says three methods offer the "most promise" for cleansing and purifying N95 masks: vaporous hydrogen peroxide (VHP), ultraviolet (UV) radiation, and "moist heat" from water heated in an oven.
Methods that NIOSH said should be avoided, because they damage the mask, include dry heat, 70% isopropyl alcohol and microwave irradiation.
Federally funded study results published this month in the CDC journal Emerging Infectious Diseases noted that using VHP resulted in the best combination of rapid decontamination and least damage to the mask. UV light killed the virus more slowly, the study said, but preserved mask function "almost as well."
The study, using 3M's Aura N95 respirators, concluded that the masks can be reused up to three times after being treated with UV or VHP.
3M does not recommend decontaminating its masks. But in light of the government guidelines on doing so, the company has been publishing technical bulletins, the latest of which finds that its N95 respirators can be cleaned without affecting the fit or function 10 to 20 times, depending on which FDA-authorized device is used.
Mary Turner, a critical care nurse at North Memorial Health Hospital and president of the Minnesota Nurses Association, said she's not happy about having to use one N95 mask over five work shifts. But it is better than having to use them for 10 shifts, as was the case at the start of the outbreak.
"I'm not going to be totally comfortable with the whole situation until we're back to using the optimal standards that we learned in nursing school," she said. "I can't say that I'm truly OK with any kind of reuse. But that being said, it is what it is."
(Staff writer Kim Hyatt contributed to this report.)
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