Clean an N95 mask in the microwave

The researchers, from Beth Israel Deaconess Medical Center, Harvard University and Massachusetts General Hospital, have detailed a reproducible decontamination approach that all health care workers would be able to utilize. “We identified an effective method of N95 decontamination by microwave-generated steam utilizing universally accessible materials. Our method resulted in almost complete sterilization after only 3 min of treatment and did not appear to affect the integrity of N95 filtration or fit with repeated treatment,” the researchers write.
We selected a generic glass container sized at 17 × 17 × 7.5 cm (length [L] × width [W] × height [H]) that had an opening large enough to expose the entire N95 respirator to the vertical column of generated steam. We secured mesh from a produce bag over the top of the container with a rubber band and added 60 ml of distilled water to the basin (Fig. 3A and B). We repeated a sterilization time course against 1-cm2 N95 respirator coupons in 1-min increments. After 2 min of microwave steam treatment, we were unable to detect residual viable phage on the coupons (Fig. 3C). This represents a 1-min reduction in sterilization time compared to the ceramic mug decontamination assay, indicating that the glass container is a more efficient decontamination system.

We found that use of a generic glass container measuring 17 × 17 × 7.5 cm (L × W × H) resulted in the most efficient and practical N95 respirator decontamination system. Using this method, we observed almost complete sterilization of the N95 respirator after a single 3-min treatment. On average, we found a 6-log10 reduction in viable MS2 phage with a minimum of a 5-log10 reduction. During decontamination treatments, we positioned the N95 respirator with its convex surface pointed downward, onto the mesh-covered container, maximizing steam exposure. Placement was otherwise made without regard to specific orientation of the respirator, simulating real world application. Posttreatment water retention by the N95 respirator was not detected, eliminating a need for drying time before reuse. Importantly, this method was validated for use of 20 times on a single respirator without detrimental effect on respirator integrity or fit. In contrast, a recent preprint demonstrated that fit and seal integrity was compromised in UV- and heat-treated N95 respirators after 3 treatment cycles and in ethanol-treated respirators after 2 treatment cycles (16). Given these findings, decontamination by microwave-generated steam may provide an ideal solution for broad N95 respirator reuse, with minimal treatment duration, minimal posttreatment processing, and maximal reuse potential.