Review of the Breathability and Filtration Efficiency of Common Household Materials for Face Masks

Abstract

The World Health Organization and the United States Centers for Disease Control have recommended universal face masking by the general public to slow the spread of COVID-19. A number of recent studies have evaluated the filtration efficiency and pressure differential (an indicator of breathability) of various, widely available materials that the general public can use to make face masks at home. In this review, we summarize those studies to provide guidance for both the public to select the best materials for face masks and for future researchers to rigorously evaluate and report on mask material testing. Of the tested fabric materials and material combinations with adequate breathability, most single and multilayer combinations had a filtration efficiency of <30%. Most studies evaluating commonly available mask materials did not follow standard methods that would facilitate comparison across studies, and materials were often described with too few details to allow consumers to purchase equivalent materials to make their own masks. To improve the usability of future study results, researchers should use standard methods and report material characteristics in detail.

Double masking protection vs. comfort—A quantitative assessment

“…However, the present technique resembles the actual scenario, and hence reported pressure drops are more realistic. The pressure drop reported for the N-95 mask (15 Pa) is very low compared to the pressure drop (210 Pa) reported using the standard technique, 50 since, in the present technique, the extended profile of the N-95 mask does not block the air at the nose exit; hence, they offer low-pressure drop, whereas in the standard technique N-95 mask material directly blocks the air at the exit. In the present case, minor flow also leaks from the periphery of the mask due to the mask fitment on the face.…”

“…The mean pressure drop for the surgical mask (105 Pa) and two-layer cotton mask (21.5 Pa) in the present case closely match with the pressure drop reported under steady flow conditions 196 and 30 Pa, respectively. 50,54 The difference is mainly attributed to the fact that in the standard technique, the face mask material is mounted perpendicular to the airflow direction and is perfectly sealed to avoid leakage. In the present case, the face mask is snugly fitted onto the face of the headform, and due to the curvature of the face and nose, there is a natural gap between the face mask and the nose exit.…”

“…The differential pressure across the face mask is a measure of breathability. 50 The differential pressure is typically measured under steady flow conditions perpendicular to the plane of the face mask material. For homogeneous material, this differential pressure is directional independent; however, for inhomogeneous material and asymmetric mask design, the differential pressure depends on airflow direction.…”

“…For homogeneous material, this differential pressure is directional independent; however, for inhomogeneous material and asymmetric mask design, the differential pressure depends on airflow direction. 50 …”

The protective performance of reusable cloth face masks, disposable procedure masks, KN95 masks and N95 respirators: Filtration and total inward leakage

“…A review article by Kwong et al . [ 101 ] has summarized a wide range of studies to provide guidance for both the public to select the best materials for face masks, and for future researchers to rigorously evaluate and report on mask material testing.…”