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is the (which was not peer-reviewed) The copyright holder for this preprint . https://doi.org/10.1101/2020.04.01.20050443 doi: medRxiv preprint electron beam irradiation or plasma generators can be expensive or dangerous), or some techniques known to cause damage to the FFR were not considered in our study. 31 Due to the shortage of FFRs, data collected was tested on a meltblown fabric (20 g/m 2 ) with initial efficiency ≥95% (full details are listed in the methods), unless otherwise specified. These samples are representative of how the filtration efficiency in a N95 FFR may change given exposure to these treatments in the worst-case scenario (i.e. no protective layer of the FFR). All meltblown samples were characterized using an industry standard Automated Filter Tester 8130A (TSI, Inc.) with a flow rate of 32 L/min and NaCl aerosol (0.26 μm mass median diameter). We subjected the meltblown samples to the aforementioned five disinfection methods and summarized the data in Table 1 . From the first disinfection, we can clearly note that the solution-based methods (ethanol and chlorine-based solution) drastically degraded the filtration efficiency to unacceptable levels, while the pressure drop remained comparable. As the pressure drop remained constant, this indicated that the loftiness and structure of the meltblown was unchanged, and the resultant efficiency degradation is the result of depolarization from the quasi-permanent polarization state of the electret ( Figure S1 ). It is hypothesized in the literature that small molecules such as solvents can permeate into the fabric and liberate the charge traps or frozen charges of the electret, 32 which would decrease the filtration efficiency. It is also possible that the chlorinebased solution may also degrade the efficiency less than the alcohol-based solution due to the higher water content. As polypropylene is hydrophobic, the chlorine-based solution may have a more difficult time in the penetration into the fabric and the static charge of fibers deeper within the meltblown may be less affected.