Decontaminating N95 and Cloth Masks-July 2020

Monthly Round Up of Important Ideas and Standards in
Industrial Hygiene and Safety

July 2020

IN THIS ISSUE: Decontaminating N95 and Cloth Masks

Approved N95 masks have been shown by the National Institute of Occupational Safety & Health (NIOSH) to be 95% efficient in controlling particulates and mists when tested. Due to the shortage of N95 masks during the COVID-19 pandemic, many employers have had to re-use masks that are recommended for one time use. According to OSHA, decontaminating filtering facepiece respirators (FFR) voids the respirators’ NIOSH approval. OSHA emphasizes that employers should look to respirator manufacturers for guidance regarding which decontamination methods are compatible with specific respirator models.

3M, one of the largest manufacturers of N95 has published a Technical Bulletin entitled “Decontamination of 3M Filtering Facepiece Respirators such as N95 Respirators in the United States-Considerations”. Unfortunately, in this bulletin, 3M repeats the OSHA warning about voiding the approval but does not give any further guidance on how to decontaminate a FFR. It does state it is working with other manufacturers and institutes to solve this problem and has individually been working for years on ways to decontaminate FFRs for years. No guidelines have been published at this time.

3M as well as OSHA, refer to a Centers for Disease Control (CDC) document, “Decontamination and Reuse of Filtering Facepiece Respirators”. It concludes that although FFRs are not approved for routine decontamination and reuse, during times of shortages, reuse may be needed. It states, “Based on the limited research available, as of April 2020, ultraviolet germicidal irradiation, vaporous hydrogen peroxide, and moist heat have shown the most promise as potential methods to decontaminate FFRs.” “Before using any decontamination method, it should be evaluated for its ability to retain 1) filtration performance, 2) fit characteristics achieved prior to decontamination, and 3) safety of the FFR for the wearer.”

Of the three recommended processes, baking N95 respirators in an oven with moist heat is the most readily available solution. Short-wave ultraviolet (UV) light has been used as a disinfectant and UV devices are inexpensive and readily available. UV light kills or inactivates microorganisms by disrupting their DNA and replication. Vaporous hydrogen peroxide disinfection systems are used in laboratory and medical facilities for sterilization but may not be available in most general industry facilities.

The CDC also has a guideline for washing cloth masks. One can wash a mask in the washing machine with other clothing or hand wash in in a bleach solution. Cloth masks can be dried in a dryer at a high hear setting or allowed to air dry in direct sunlight.

Although N95 manufacturers at this time have been silent on how to reuse their disposable devices, the CDC has been providing guidance on how to best disinfect N95 and cloth masks. The use of masks along with social distancing is shown to help fight the COVID-19 pandemic.

Be smart, be well, be six feet apart

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