Table 3.

Summary of mask decontamination methods.

Decontamination method	Equipment needed	Effect on viral and bacterial inactivation	Impact on particle filtration efficiency (PFE)	Impact on physical properties of masks	Safety risk and other considerations
Ultraviolet germicidal irradiation (UVGI)	•UVC source (e.g., mercury lamp)	•>3-Log reduction of H1N1 at 1 J/cm2 for 60–70s [106] •More resistance for larger organisms [103]	•No effect at 176–181 mJ/cm2 for 15 min[ 107 ] •Slight decrease in PFE (~1%) at high dose of 120 J/cm2 [104]	•Loss of N95 strength at 120 J/cm2 [104] •Damage of polymer and straps [103]	•UV light may be blocked or unevenly distributed due to creases in masks
Dry heat treatment	•Oven (lab-grade, kitchen, etc.)	•SARS-CoV-2 is inactivated at 70 °C for 60 min [115]	•N95 PFE >98% at 70 °C for 90 min [116]	•Metal bands are deformed at 80 °C •Microwave oven led to N95 melting [106] •Reduced ΔP [115]	•Excess heat (> 80 °C) leads to mask damage [106]
Moist heat treatment	•Oven (lab-grade) •Kitchen steamer •Microwave generated steam (MGS)	•>6 times decrease in SARS-CoV-2 at 70 °C treatment for 5 min •>5-Log reduction in MS2 and S. aureus for steamer •5-Log reduction of H1N1 for MGS at 1250 W for 2 min [103]	•N95 PFE >95% at 70 °C and and 50% RH for 60 min [115]	•No effect on fit or other physical properties at 70 °C and 50% RH for 60 min [115] •No visible changes after 5 cycles of 5 min steam •Areas around N95 metallic noseband melt with MGS [107]	•Moisture leads to de-charging of mask electrets [149]
Vaporized hydrogen peroxide (VHP)	•FDA-approved decontamination •Commercially available as the Battelle Critical Care Decontamination System (CCDS)™	•>5-Log reduction in SARS-CoV-2 RNA on tested N95 masks [151]	•N95 PFE >95% at 8% H2O2 [123,124] •PFE of surgical masks reduces significantly [124]	•Metallic nosebands are tarnished [107] •No effect on ΔP	•CCDS is expensive [101] •H2O2 may be deactivated by organic debris (e.g., dirt) [103]