Rapid evidence summary on SARS-CoV-2 survivorship and disinfection, and a reusable PPE protocol using a double-hit process

José G B Derraik; William A Anderson; Elisabeth A Connelly; Yvonne C Anderson

• The applied UVC dose should be at least 1,000 mJ/cm 2 , but we recommend an initial conservative dose of 2,000 mJ/cm 2 [applied to each side of N95 FFRs, i.e. wearer-facing and outer sides] to account for possible errors in applied dose estimation, effects of different materials, the challenge to reach the inner filtering layers of FFRs 25 , as well as the uncertainty regarding the actual susceptibility of SARS-CoV-2 to UVGI. • We also recommend heat treatment at 60°C for 90 minutes to treat PPE. This is most likely a very conservative protocol when applied to surface contamination, but in the absence of more precise data, we recommend erring on the side of caution. The 90minute period of exposure is advisable to ensure there is adequate heat transfer to the inner layers of the FFRs, particularly if a number of masks are being treated at the same time (in which case we would caution against stacking them). • While we cannot recommend a target relative humidity due to the paucity of data for SARS-CoV-1, moderate levels are likely to be more desirable (i.e. 40% to 50%). • We advise against attempts to disinfect and reuse soiled PPE, as studies using both UVGI and heat treatment show a protective effect of protein and aqueous substrata on SARS-CoV-1 survival. • Unpublished experimental data from our group showed that there is minimal UVC radiation on the wearer-facing side of N95 FFRs when the outer side is irradiated (outer 7.34 mW/cm 2 vs inner 0.10 mW/cm 2 ). There are reports of widespread SARS-CoV-2 infection among frontline medical staff 32 , thus, it has to be assumed that SARS-CoV-2 contamination of N95 FFRs would likely occur on both sides, particularly when there . CC-BY-NC 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.