. 2020 Jul 8;48(12):1520–1532. doi: 10.1016/j.ajic.2020.07.004

Table 1.

Summary of advantages and disadvantages of decontamination methods that might allow N95 filtering facemask respirators (FFRs) to be reused

Method of decontamination	N95 FFR models tested	Advantages	Disadvantages/ N95 models with their disadvantages
Ultraviolet germicidal irradiation (UVGI)	3M 1860 3M 1870 3M 8000 3M 8210 3M 9210 3M 9211 3M VFlex 1805 Alpha Protech 695 Gerson 1730 Kimberly-Clark 46727 Kimberly-Clark PFR95-270 Moldex 1512 Moldex 1712 Moldex EZ-22 Moldex 2200 Precept 65-3395 Prestige Ameritech RP88020 Sperian HC-NB095 Sperian HC-NB295F U.S. Safety AD2N95A U.S. Safety AD4N95 N95-A N95-B N95-C SN95-D SN95-E SN95-F GE 1730 KC 46727 4C Air, Inc. (GB2626 KN95) ESound (GB2626 KN95) Onnuriplan (KFDA KF94)	Significant reductions in Influenza virus recovery and viability even under soiled conditions¹⁷ Substantial reduction in the recovery of pathogens such as Bacillus subtilis spores after exposure to UVGI for as little as 5 minutes¹⁸ Inactivation of influenza A (H1N1), avian influenza A (H5N1), influenza A (H7N9) A/Anhui/1/2013, influenza A (H7N9) A/Shanghai/1/2013, MERS-CoV, SARS-CoV, and SARS-CoV-2¹⁰^,¹⁹ No significant effect on filter aerosol penetration, filter airflow resistance, fit and seal, odor, discomfort, difficulty in donning, or physical appearance after up to 20 of cycles of decontamination10, 11, 12, 13, 14, 15^,²⁵ No significant effect on filtration efficiency after 10 cycles of decontamination.²⁰	Reduction in the strength of the layers of FFR material (at higher UVGI doses)/ (3M 1860, 3M 9210, Gerson 1730, Kimberly-Clark 46727)¹⁵ UVGI efficiency hampered by shadowing produced by the multiple layers of the N95 FFRs/(all FFR models)¹⁷ UVGI performance can vary among different models of N95 FFRs, different parts of the respirators, distinct types of UVGI, and number of cycles of decontamination Considerable impact on the strap tension of some N95 FFR models (with 20 cycles of decontamination)/ (3M 1860, 3M 1870, Kimberly-Clark PFR)¹⁰ Better reduction in B. subtilis recovery with UV-C than with UV-A/ (3M 8210)¹⁸ UV-treated FFRs were able to withstand 10 cycles of treatment, but efficiency eventually decayed to 93% at 20 cycles, making it unsuitable for N95-grade FFRs by itself/ (3M 8210, 4C Air, Inc. (GB2626 KN95), ESound (GB2626 KN95), Onnuriplan (KFDA KF94)).²⁰
Vaporized hydrogen peroxide (VHP)	3M 1860 3M 1870 3M 9211 N95-A N95-B N95-C SN95-D SN95-E SN95-F	Complete inactivation of G. stearothermophilus spores following 50 repeated aerosol inoculation/decontamination cycles²¹ Complete eradication after a single VHP cycle of 3 aerosolized bacteriophages (T1, T7, and Pseudomonas phage phi-6)²² Extremely rapid inactivation of SARS-CoV-2 both on N95 and on stainless steel.¹⁹ No significant effects on filtration performance, filter aerosol penetration, fit, and filter airflow resistance after up to 50 cycles of decontamination²¹ No vapors potentially toxic to humans nor environmentally hazardous residues as a result of the VHP decontamination process¹¹	Fragmentation of the elastic material in the straps when stretched (after 30HPV, but not after 10 or 20 VHP cycles)/ (3M 1860)²¹ Slight tarnishing of the metallic nosebands/ (all FFR models)¹³
Ethylene oxide (EtO)	N95-A N95-B N95-C SN95-D SN95-E SN95-F	No significant affection of filter aerosol penetration, filter airflow resistance, or physical appearance of the FFRs¹¹^,¹³^,¹⁶	None
Microwave oven use	3M 1860 3M 1870 N95-A N95-B N95-C SN95-D SN95-E SN95-F 3M 1860 3M 1870 3M 8000 3M 8210 Moldex 2200 Kimberly-Clark PFR95-270 Cardinal Health N95	Satisfactory decontamination against influenza virus on N95 FFRs as measured by a virus culture method¹² High efficacy for inactivating bacteriophage MS2 droplets as a surrogate for a pathogenic virus on FFRs²³ No significant affection of filter aerosol penetration or filter airflow resistance of FFRs (after 2 minutes of microwave exposure)11, 12, 13^,¹⁶ No significant reduction in fit, increase in odor, increase in discomfort, or increased difficulty in donning¹⁴ No known health risks to the users¹³	Melting of the filter media at the ends of the aluminum nosebands, forming visible holes. Significant increase in filter penetration (after 4 minutes of microwave exposure)/ (all FFR models)¹¹ Partial separation of the inner foam nose cushion and slight melting of the head straps from some FFR samples/ (SN95-E and SN95-D, respectively)¹⁶ Microwave oven irradiation melted samples from 1 FFR model/ (SN95-E)¹³ Filtration material melted in areas adjacent to the metallic nosebands/ (SN95-E)¹³
Bleach	N95-A N95-B N95-C SN95-D SN95-E SN95-F 3M 8210 4C Air, Inc. (GB2626 KN95) ESound (GB2626 KN95) Onnuriplan (KFDA KF94)	99-100% biocidal efficacy, indicating effective sterilization of Bacillus subtilis spores¹⁸ No significant affection of filter aerosol penetration or filter airflow resistance	Tarnishing of the aluminum nosebands/ (all FFR models)¹¹^,¹³^,¹⁶ Stiffening of the filter media and elastic straps (treatment with 5.25% bleach)¹¹ Discoloration of the inner nose cushion of 1 of the 3 N95 FFRs evaluated/(SN95-E)¹³ Characteristic smell of bleach/(all FFR models)¹³ Oxidation of staples/ (N95-B, N95-C, SN95-E, SN95-F)¹⁶ Dissolution of nose pads/ (SN95-E)¹⁶ Discoloration (yellowing) of inner nose pads/ (N95-A, SN95-E, SN95-F)¹⁶ Discoloration of other areas of the FFR (bleeding of printed ink lettering)/ (SN95-F)¹⁶ Yellowing of the material adjacent to nose pad/ (SN95-E)¹⁶ From the first disinfection, bleach drastically degraded the filtration efficiency/ (3M 8210, 4C Air, Inc. (GB2626 KN95), ESound (GB2626 KN95), Onnuriplan (KFDA KF94)).²⁰
Heath treatment	3M 1860 3M 1870 3M 8000 3M 8210 3M 9211 N95-A N95-B N95-C SN95-D SN95-E SN95-F Moldex 2200 Kimberly-Clark PFR95-270 4C Air, Inc. (GB2626 KN95) ESound (GB2626 KN95) Onnuriplan (KFDA KF94)	Satisfactory decontamination of influenza virus on N95 FFRs as measured by a virus culture method¹² No significant affection of filter aerosol penetration of FFRs¹²^,¹⁶^,¹⁹ No significant affection of filter airflow resistance of FFRs¹⁶ No observable physical change in FFRs¹⁶ No clinically significant reduction in fit, increase in odor, increase in discomfort, or increase in difficulty in donning¹⁴ No significant affection of filtration efficiency or pressure after 10 cycles of decontamination.²⁰	Increase in filtration penetration (at a temperature of 80°C)¹¹ More than 1 cycle of decontamination caused sharp drops in the filtration performance of N95 FFRs/ (3M 9211)¹⁹ N95 FFRs were largely melted and unusable after only 22 minutes of treatment at 160°C¹¹ Partial separation of the inner foam nose cushion and slight melting of the head straps from some FFR samples/ (SN95-E and SN95-D, respectively)¹⁶
Ethanol	3M 8210 3M 9211 4C Air, Inc. (GB2626 KN95) ESound (GB2626 KN95) Onnuriplan (KFDA KF94)	Extremely rapid inactivation of SARS-CoV-2 both on N95 and on stainless steel¹⁹ Filtration performance of N95 FFRs was not markedly reduced after a single decontamination with 70% ethanol¹⁹	Higher survival of Bacillus subtilis spores than with other decontamination methods/ (3M 8210)¹⁸ More than 1 cycle of decontamination caused sharp drops in the filtration performance of the ethanol-treated masks/(3M 9211)¹⁹ From the first disinfection, ethanol drastically degraded the filtration efficiency/(3M 8210, 4C Air, Inc. (GB2626 KN95), ESound (GB2626 KN95), Onnuriplan (KFDA KF94)).²⁰
Liquid hydrogen peroxide (LHP)	N95-A N95-B N95-C SN95-D SN95-E SN95-F	No significant affection of filter aerosol penetration of FFRs¹¹^,¹⁶ No significant affection of filter airflow resistance of FFRs¹⁶	Slight fading of the label ink on the fabric of FFRs (treatment with 6% LHP for 30 minutes)¹¹ Oxidation of the staples to varying degrees (for those models that use staples)/ (N95-B, N95-C, SN95-E, SN95-F)¹⁶
Autoclave	3M 8210	Effective sterilization of almost 100% of Bacillus subtilis spores¹⁸	N95 FFRs were deformed, shrunken, stiff, and mottled (for both 15- and 30 minutes of treatment)¹¹ Marked increase of filter aerosol penetration of FFRs (for both 15- and 30 minutes of treatment)¹¹
Isopropyl alcohol	N95 (model not specified)	None	Fading of strap ink of FFRs¹¹ Marked increase of filter aerosol penetration of FFRs (for both 1 second and 1 minute of treatment)¹¹
Wipe products	3M 1860 3M 1870 Kimberly-Clark PFR	No mucin detected in replicates using the 0.9% hypochlorite wipes²⁴ Mean removal efficiency of S. aureus by 0.9% hypochlorite wipes ranged from 98.98 to >99.99%²⁴	Removal of S. aureus less effective from nose pads and perforated edges/ (Kimberly-Clark PFR)²⁴ Mean removal efficiency of mucin by benzalkonium chloride and inert wipes ranged from 21.47% to 76.41%²⁴ Benzalkonium chloride wipes caused more penetration than the other wipes/ (all FFR models)²⁴
Tap water	N95 (model not specified)	Average filter penetration was unchanged for N95 FFRs¹¹ No significant visible changes in FFRs detected¹¹	None
Soap and water	N95 (model not specified)	No visible changes detected in FFR samples¹¹	Average penetration markedly increased for N95 FFRs at both time intervals (2- and 20 minutes)¹¹
Traditional electric rice cooker	3M 8210	Effective sterilization of almost 100% of Bacillus subtilis spores¹⁸	None