Comparison of Two Methods for Sterilization of Filtering Facepiece Respirators Worn for Extended Periods During the COVID-19 Pandemic: An Experimental Laboratory Study

During the COVID-19 pandemic, there was a shortage of Filtering Facepiece Respirators (FFR), leading to prolonged use and reuse of FFRs. FFRs were collected in three hospitals after extended use (up to 15 or 30 days). We assessed the physical characteristics and filtration levels of worn FFRs, before sterilization. Respirators that achieved at least 94% filtration of aerosol particles, nasal clip still attached, had no tears, had preserved elastic bands and had no dirt were randomized to receive or not receive cleaning before being submitted to hydrogen peroxide plasma gas sterilization. A total of 1,055 FFRs were collected. Over 85% of them exhibited secured nose clips, preserved strap elasticity, and no tears. However, more than 78% of samples contained dirt, leaving only 101 (19.6%) eligible to undergo sterilization. After sterilization, none of the FFRs in either group achieved minimum filtration, although 72% without cleaning and 80% with cleaning had filtration between 90.0 and 93.9%. A large proportion of FFRs were ineligible for sterilization due to factors unrelated to healthcare (e.g., dirt from makeup). Prolonged reuse of FFRs significantly reduced aerosol filtration efficiency. Eligible FFRs did not maintain 94% filtration after sterilization with or without cleaning.