SARS-CoV-2 is an RNA virus that has a diameter of approximately 0.1 µm. It is transmitted by respiratory droplets and aerosols such that one of the most effective ways to prevent infection is to wear filtering facepiece respirators (FFRs). The commonly used FFRs are N95 respirators, devices that by design filter 95% or more of particles larger than 0.3 µm in diameter. In practice, these devices prevent the passage of 99.8% of particles large than 0.1 µm. RNA viruses are inherently unstable, and transmission of viable SARS-CoV-2 can occur only if the virus is protected from the atmosphere by being contained within moist respiratory droplets or aerosols. The droplets are of various sizes, with large droplets being on the order of 5 µm or larger. Respiratory aerosols can transmit the virus great distances and have particle sizes of about 1 µm. All of these particle sizes are effectively filtered by N95 respirators, as long as they closely fit the contours of the wearer’s face, avoiding leaks around the filter material.

To date, several approaches have been tested for the reprocessing of N95 respirators and how they affect filtration efficiency and facial fit characteristics. They include UV germicidal irradiation (UVGI), vaporized hydrogen peroxide (VHP), moist-heat incubation (MHI), microwave-generated steam (MGS), and ethylene oxide. How to select the optimal method is uncertain. To determine which method is most clinically useful, a systematic review was performed to assess the efficacy and feasibility of each reprocessing strategy.

Because FFR devices are made of a variety of materials and constructed in different ways, clinicians should establish that the reprocessing system in use at their facility has been tested for the specific make and model of the N95 respirator. The CDC recommends that the manufacturer be consulted about the effect of the chosen decontamination process method for the specific respirator model before reprocessing is attempted in the clinical setting. If the manufacturer cannot provide this information, the methods used to test the efficacy of reprocessing systems reported in the study (link below) should be implemented by local facilities to ensure the safe operation of reprocessed FFR devices.