Can N95 respirators be reused after disinfection? And for how many times?

Lei Liao; Wang Xiao; Mervin Zhao; Xuanze Yu; Haotian Wang; Qiqi Wang; Steven Chu; Yi Cui

is the (which was not peer-reviewed) The copyright holder for this preprint To determine the upper limit of applicable temperature, we tested low humidity conditions (≤30% RH) up to 125 °C (10 minutes/cycle), plotted in Fig. 4g -h (data provided in Table S3 ). There is little to no change in the filtration efficiency and pressure drop up to 100 °C in low moisture conditions. However, at 125 °C, there is a sharp drop in the filtration efficiency while maintaining a constant pressure drop at around cycle 5. Similarly, the lack of pressure drop change indicates that the degradation is also due to the static decay. Considering the higher temperature, polypropylene's melting point (130-170 °C), as well as the thin and fibrous nature of the media, it is possible that the higher temperature is enough to relax the microscopic charge state within the polymer resulting in some of the quasi-stable polarization to become depolarized to their neutral state. From SEM images, we did not identify any morphological changes and did not observe any apparent physical deformations ( Figure S3 ), which may support this conclusion. This effect is not as strong as direct solvent contact, which reduced the filtration efficiency to <80%, while 125 °C reduced the efficiency to ~90%. The mechanism of depolarization may differ, as the solvent can liberate charge traps, but the temperature here provides energy to return some of the fibers' polarized state to a relaxed state.