Method #1: 70 – 75% Ethanol Bath Followed by Drying
- Decontamination: Ethanol has been found to be effective in viral decontamination after as little as 10 minutes of exposure (Fischer 2020)
- Integrity: Filtration efficacy fell below 95% after a single decon cycle (56%) (Stanford Medicine 2020)
- Recommendation: Ethanol Bath is not a safe method for decon as it results in non-protective masks after a single decon cycle.
Method #2: Dry Heat – 70oC
- Decontamination: 60 minutes of heating at 70oC (158oF) is effective in viral decontamination of the N95 mask but may leave residual virus on metal portions (ie nasal bridge piece) (Fischer 2020)
- Integrity: Adequate mask integrity was preserved for up to two decon cycles (Fischer 2020)
- Recommendation: Convection heating (not your typical home oven as temperatures in these cannot be maintained minute to minute) at 70oC is effective and yields a usable mask. This approach should not be performed more than twice on any given mask.
Method #3: Autoclave
- Decontamination: 15 minutes at 121oC (total cycle time of 40 minutes) was effective in decontamination (Kumar 2020)
- Integrity: All 3M masks tested in the Kumar study maintained integrity after a single decon cycle but, fit was lost in one of the most common models (3M 1860) by 3 cycles
- Recommendation: Autoclave can be safely used for a single decon cycle but the ability to use it for multiple decon cycles will depend on the mask in question
Method #4: Time
- Background: Though data is limited, available evidence shows that SARS-CoV-2 can persist on inanimate surfaces for up to 72 hours. The infectiveness of virus on these surfaces at any time interval is unknown.
- Idea: Cycle through masks where each mask gets at least 72 hours of non-use after a day of use
- Start on day#1 with 4 N95 masks
- Use mask #1 on day #1. After use, store in a dry atmosphere for 3-4 days
- Reuse after at least 72 hours
- Note: I (Anand Swaminathan) have been using this approach since the beginning of the pandemic. I have used each mask for a total of 4 times (3 decon cycles)
- Attribution: Thanks to Dr. Jessica Lopez who chatted with N95 technology inventor Dr. Peter Tsai about this approach
Method #5: UV Light (260-285 nm)
- Decontamination: 60 minutes of exposure effectively decontaminated the mask though the metal portions only required 10 minutes (Fischer 2020). Prior work showed safety with only 30 minutes of exposure (Stanford 2020)
- Integrity: Adequate mask integrity was preserved for up to three decon cycles (Fischer 2020)