Is the Current N95 Respirator Filtration Efficiency Test Sufficient for Evaluating Protection Against Submicrometer Particles Containing SARS-CoV-2?

Cai, C.; Floyd, E. L.; Aithinne, K. A.; Oni, T.

Previous researchers measured the Overall Filtration Efficiency using sodium chloride testing aerosol with aerosol photometer to analyze the reuse of respirators after sterilization. However, this study showed that the Overall Filtration Efficiency would significantly overestimate the respirators' ability to protect against submicrometer particles containing SARS-CoV-2. For example, after three cycle H2O2 vaporous sterilizations, the most penetrating particle size for the N95 level respirators was from 250 nm to 500 nm, which carried the peak concentration of the SARS-CoV-2 in hospitals. The Size Specific Filtration Efficiency (250 nm to 500 nm) dropped to 56%{+/-}4%, however, the Overall Filtration Efficiency was still 86%{+/-}5%. In order to protect health care personnel adequately, we recommend measuring the Size Specific Filtration Efficiency to evaluate the reuse of respirators.