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Underground N95 Insert

Hello! Here are your five N95 masks.* 

We recommend that you get fit tested at your institution to ensure they work appropriately.  As per manufacturer recommendations, N95 masks are designed for one-time use. 3M, a prominent producer of N95 masks, performed internal testing of various sterilizing strategies and does not endorse any of them.[1] However, in times of scarcity, the strategies below are options that can be considered based on individual clinical judgment and the institutional resources available.

Below is an adaptation of N95 re-use strategies from SAGES



The number of times a mask can safely be re-used depends on multiple factors, eg, exposure to aerosolizing procedures; how the mask was stored, and whether the mask was soiled. Assuming there is no soiling and minimal to no viral contamination to the outside of the mask, the CDC suggests that masks can be hung to dry or stored in a breathable container in between uses. Our strategy is based on the fact that coronaviruses lose their viability significantly after 72 hours[2],[3]. When planning to reuse a N-95 mask, removal of the mask should be done strictly to avoid contamination of the inside of the mask during placement or removal (see below methods for donning and doffing).



Mask Rotation: Your 5 Masks**

This method involves acquiring a set number of N95 masks (the American College of Surgeons recommends up to 7), and rotating their use each day, allowing them to dry for long enough that the virus is no longer viable. According to Dr. Peter Tsai, the inventor of the filtration media contained in the N95, “Polypropylene in N95 masks is hydrophobic, and contains zero moisture. COVID-19 needs a host to survive–it can survive on a metal surface for up to 48 hours, on plastic for 72 hours, and on cardboard for 24 hours. When the respirator is dry in 3-4 days, the virus will not have survived.”[4]

***Your greatest risk of contamination is during donning and doffing***
There are various online videos with methods of donning and doffing that help to minimize contact to the front of the mask. Here is a representative example: (QR code above)

After using each mask 2-3 times, we recommend getting a new set.  Please email us at to get a new set. 



Dr Cheryl Wu & Dr Nancy King

*These N95 masks are not hospital verified.  Use at your own risk. Please let us know if you know anyone who has a fit tester!!!

**There are other methods of decontamination, but as these usually require commercial machines, we recommend sticking with the mask rotation as the most reliable method.  If you’re interested - you can explore the other methods at:  

[2] van Doremalen N, Bushmaker T, Morris DH, et al. Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1 [published online ahead of print, 2020 Mar 17]. N Engl J Med. 2020;10.1056/NEJMc2004973. doi:10.1056/NEJMc2004973
[4] Correspondence posted by Dr. Amanda Deskins on March 23, 2020 in the following JAMA Editorial:

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