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While the U.S. Food and Drug Administration (FDA) says health care workers should ideally use new personal protective equipment amid the coronavirus pandemic, strained supplies have caused the agency to weigh safe alternatives for reuse, such as dry heat.

“While [health care personnel] should continue to use a properly fitting, new, FDA-cleared or authorized respirator when available according to existing health care organization protocols, in the case that there is a supply shortage, reuse of decontaminated or bioburden-reduced respirators are [a] potential option,” per new guidance issued Wednesday.

“Under certain circumstances, single-use, disposable [filtering facepiece respirators,] [which includes N95s,] may be reused for a limited number of times if properly decontaminated or have undergone sufficient bioburden reduction,” reads the guidance.

The FDA says dry heat can help lower the bioburden (or microorganisms present) on respirators like N95s to save on supplies amid potential shortages.

The FDA said systems using dry heat are OK when:

  • Consistent temperatures of 70 degrees Celsius for at least 60 minutes for enough bioburden reduction, or 75 degrees Celsius for 30 minutes
  • Close assessment of chamber temperatures ensure even heat distribution
  • There is a “highly controlled heat transfer” (like in a lab oven or industrial convection oven)
  • The system isn’t a household appliance like an oven or pressure cooker due to imprecision in temperature control and the possibility of cross-contamination

However, the agency advised tossing masks in certain situations, like during aerosol-generating procedures (common in dentistry), masks that become difficult to breathe through and also masks contaminated with blood or other bodily fluids from patients, among other circumstances.

On a side note, the Centers for Disease Control and Prevention (CDC) previously advised health care workers to store used-N95s in a “breathable paper bag” after work shifts with at least five days between each use, along with frequent hand hygiene to prevent spreading the pathogen to the wearer.

“This will provide some time for pathogens on it to ‘die-off’ during storage,” the CDC wrote on its webpage. The agency also advised against wearing the same mask more than five times.

The FDA said Wednesday that its new guidance, which you can read more about here, should be followed “in conjunction with, not in lieu of, the existing CDC reuse recommendations.”

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