Evaluation of filtration characteristics and microbial recovery rates of commercial filtering facepiece respirators against airborne bacterial particles
Many brands of filtering facepiece respirators are used against air pollution, including bioaerosols; however, studies have explored exposure to bioaerosols from the inside surfaces of respirators. We evaluated the filtration efficiencies and microbial recovery rates of commercial filtering facepiece respirators against bioaerosols. Eight filtering facepiece respirators and one surgical mask were selected, all with high market shares in the Republic of Korea and certified by national or international standards. The tested filtering facepiece respirators were installed on the head of a mannequin under various airflow velocity and relative humidity (RH) conditions. The filtration efficiency against Staphylococcus epidermidis and Escherichia coli bioaerosols, the pressure drop of the filter, and the relative recovery rates for the bacteria were evaluated. The filtration efficiency of each filtering facepiece respirator ranged from 82% to 99%, depending on the filtration grade. The pressure drop was significantly affected by variations in the surrounding RH. The mean relative recovery rates of all filtering facepiece respirators were 14 ± 4.8% and 9 ± 4.7% for S. epidermidis and E. coli, respectively. These results indicate that airborne microorganisms can survive and accumulate on the surfaces of filtering facepiece respirators, which may lead to harmful health outcomes. Our findings will be useful as background information for the development of commercial filtering facepiece respirators while considering their biological properties and reliable guidance to users.