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

• Table 4 describes five studies that examined the effects of heat treatment on the performance and structure of N95 FFRs. • Two studies looked at dry heat treatment at 80°C 17,37 , reporting no meaningful effects on filter particle penetration and leading to no obvious signs of damage (Table 4 ). • Three studies looked at moist heat incubation at 60°C and 80% relative humidity, two for 15 minutes 38,39 and one for 30 minutes 40 (Table 4 ) -there were no meaningful effects on filter aerosol penetration or filter airflow; most FFRs were undamaged, but in the three studies there was separation of the inner foam nose cushion from the FFR body in one particular model. • While two studies have looked at the effects of 3 heat treatment cycles for 15 minutes 38 and 30 minutes 40 at 60°C on N95 FFRs, no peer-reviewed studies seem to have looked at the potential effects of more than 3 heat treatment cycles or multiple cycles of longer duration on N95 FFRs. The exception is Liao et al. (2020) 41 , who have recently reported that 20 cycles of dry heat at 75°C for 30 minutes did not affect the filtration efficacy of the key fabric in N95 FFRs. However, due to their methodology it was not possible to ascertain whether the fit of the masks for example, would be affected by their treatment protocol. • It is worth noting that N95 FFRs are mostly made of polypropylene 42 , whose maximum operating temperature is approximately 80°C 43 , so that heat treatment approaching this temperature is probably illadvised.