Effect of Dry Heat and Autoclave Decontamination Cycles on N95 FFRs

Abstract

Current shortages of Filtering Facepiece Respirators (FFRs) have created a demand for effective methods for N95 decontamination and reuse. Before implementing any reuse strategy it is important to determine what effects the proposed method has on the physical functioning of the FFR. Here we investigate the effects of two potential methods for decontamination; dry heat at 95 °C, and autoclave treatments. We test both fit and filtration efficiency for each method. For the dry heat treatment we consider the 3M 1860, 3M 1870, and 3M8210+ models. After five cycles of the dry heating method, all three FFR models pass both fit and filtration tests, showing no degradation. For the autoclave tests we consider the 3M 1870, and the 3M 8210+. We find significant degradation of the FFRs following the 121 °C autoclave cycles. The molded mask tested (3M 8210+) failed fit testing after just 1 cycle in the autoclave. The pleated (3M 1870) mask passed fit testing for 5 cycles, but failed filtration testing. The 95 °C dry heat cycle is scalable to over a thousand masks per day in a hospital setting, and is above the temperature which has been shown to achieve the requisite 3 log kill of SARS-CoV-2[1], making it a promising method for N95 decontamination and reuse.

A systematic review of mask disinfection and reuse for SARS-CoV-2 (through July 10, 2020)

“…Overall, 16 studies measured disinfection and durability 12, 15, 19, 20, 22, 27-30, 33, 36, 47, 49, 51, 62, 64 , 16 studies measured only disinfection 13, 18, 23, 24, 31, 38, 40, 41, 43, 44, 48, 56, 63, 65-67 and 26 studies measured only durability 7, 14, 16, 17, 21, 25, 26, 32, 34, 35, 37, 39, 42, 45, 46, 50, 52-55, 57-61, 68 . Thus, 32 studies measured disinfection and 42 measured durability.…”

“…Autoclaving (n=14) 14, 30, 34, 42, 45, 55, 57, 59 and ethanol disinfection (n=14) 15-17, 29, 42, 45, 53, 58 led to failures within two disinfection cycles in 12 and 13 tests, respectively. This indicates these methods cannot be utilized for N95 reuse.…”

“…Given the wide differences in test conditions, results are summarized by disinfection agent for N95s only, for agents with >5 samples or those agents identified in the disinfection efficacy section as achieving >3 log reduction of SARS-CoV-2, including ethanol, hydrogen peroxide, peracetic acid, PX-UV, UVGI, autoclaving, and heat. Autoclaving (n=14) 14,30,34,42,45,55,57,59 and ethanol disinfection (n=14) 15-17, 29, 42, 45, 53, led to failures within two disinfection cycles in 12 and 13 tests, respectively. This indicates these methods cannot be utilized for N95 reuse.…”

Decontamination of N95 Respirators using Moist Heat Delivered by Hospital Blanket Warming Cabinets: A Widely Available Method for N95 Re-Processing

“…For example the use of UV respirator treatment is limited by the availability of appropriate UV lamps and concern about their ability to deliver sterilization beyond the exposed respirator surface [3]. Autoclave treatment is broadly available but utility is limited to a subset of pleated (rather than molded) construction [3,12]. Vaporized or gaseous hydrogen peroxide methods require relatively expensive and complex devices that may be in limited supply in the current circumstance.…”

Humidity and deposition solution play a critical role in virus inactivation by heat treatment on N95 respirators

“…Heat remains a widely accessible strategy for decontamination of PPE due to the ubiquity of ovens that can achieve sufficient temperatures and the ease of translating and communicating effective protocols. Furthermore, the temperatures and treatment times used in this study do not negatively impact respirator integrity (2, 16, 38), which is essential for this method’s applicability. To support the use of effective N95 decontamination approaches during the COVID-19 pandemic, the USFDA provided a number of emergency use authorizations (EUAs) and published recommendations for evaluating N95 decontamination methods.…”