Instapot sterilization of respirators

I'm using the pure pressure function of my Insta-Pot for sterilization.  The standard 1 cup of water, then the trivet, then a cotton face towel, then five commercial respirators, then wrap the face towel over the top of the flattened respirators. Like so:


I think (but am not sure) that the pressure hits 15 PSI, then drops to normalize at 10 - 11.5 PSI. That in turn means a temperature of 116-117 °C (239 to 243 °F) *. I'm programming it for two minutes at full pressure. The idea is to let the pressure drop without venting, then remove the masks. The masks emerge fine - very nearly dry.   I'm a bad scientist though and in that half the runs I let the pressure drop on its own, and half the time I vented the steam to make extraction quicker.

I hang them for 10 mins then embark on PortaCount testing (8020A made in 1998).


Results so to five goes for all bar one of the masks:



Sterilization of commercial respirators via this heat treatment looks good.  The surgical mask and the KF95 are losing strength in the nose wire in the latter tests and have edge leaks but the fabric on its own is retaining filtration. Could be gaining filtration but it is difficult to say that. I'm sitting still and not speaking for the tests, and I might be getting better at pressing the masks into place with each go.

The FFP3 (GVS F31000) lost its inner nose pad after 1 cleaning. The heat was too much for the glue, but the loss of that piece didn't really affect performance.  On cleaning #5 it dropped to 95% PFE but that use of pressure cooker was flawed as I tried to thread a meat thermometer in through the rubber gaskit and all that did was generate a super amount of steam at 99.4 °C until all the water had gone.

The masks:


The GVS and AirQueen look most beaten up after the InstaPot action.  

Elastomeric Respirator


I tested an entry level GVS Eclipse today too: 99.9971% (average before cleaning)

After the same sterilization routine:

Run 1: 99.8846%  

Run 2: 99.9525%  

Run 3: 99.9380%  

Run 4: 99.9638%  

Run 5: 99.9751%  

Run 6: 99.9817%  

Run 7: 99.9876%  

Run 8: 99.9868%  

Overall Ave: 99.9595%

Related studies:

1. Dry Heat as a Decontamination Method for N95 Respirator Reuse

Chamteut Oh, Elbashir Araud, Joseph V. Puthussery, Hezi Bai, Gemma G. Clark, Leyi Wang, Vishal Verma, and Thanh H. Nguyen






2. Dry heat and microwave-generated steam protocols for the rapid decontamination of respiratory personal protective equipment in response to COVID-19-related shortages

M.J. Pascoe,A. Robertson, A. Crayford, E. Durand, J. Steer, A. Castelli, R. Wesgate,S.L. Evans, A. Porch, and J-Y. Maillard, 


 

3. Dry heat sterilization as a method to recycle N95 respirator masks: The importance of fit

 




4. Dry Heat Disinfecting of N95 Masks Works, Preserves Fit

Peter Genzer


5. Microwave-Generated Steam Decontamination of N95 Respirators Utilizing Universally Accessible MaterialsKatelyn E. Zulauf, Alex B. Green, Alex N. Nguyen Ba, Tanush Jagdish, Dvir Reif, Robert Seeley, Alana Dale, James E. Kirby 



6. COVID-19 global pandemic planning: Dry heat incubation and ambient temperature fail to consistently inactivate SARS-CoV-2 on N95 respirators

Douglas J Perkins , Robert A Nofchissey , Chunyan Ye , Nathan Donart , Alison Kell , Ivy Foo-Hurwitz , Timothy Muller, Steven B Bradfute


7. Decontamination and Reuse of N95 Masks: A Narrative Review
M. A. Khan, A. Ikram, S. Savul, F. K. Lalani, M. A. Khan, and M. Sarfraz

8. Decontamination of surgical face masks and N95 respirators by dry heat pasteurization for one hour at 70°C

Yi Xiang, Qifa Song,,⁎ and Wenzhen Gu, 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7260521/


 

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