A Study on Performance and Reusability of Certified and Uncertified Face Masks

Abstract

In this study, the performance (particle removal efficiency and breathing resistance) of several commercially available face masks (KF80-certified electrostatic and nanofiber filter masks, and an uncertified mask) was evaluated, along with their filter structure and composition. Also, the effects of the relative humidity (RH) of incoming air, of water and alcohol exposure, and of reuse, on the performance of face masks were examined. Monodisperse and polydisperse sodium chloride particles were used as test aerosols. Except for the uncertified mask filter, PM2.5 removal efficiency was > 90%. The nanofiber filter mask had the highest quality factor due to its low pressure drop and high removal efficiency, and densely packed nanofiber pore structure, and significant amounts of fluorine, carbon and oxygen. The removal efficiency of the KF80-certified mask was barely affected by the higher RH of incoming air. When the mask filters were soaked in water, their removal efficiency decreased. The uncertified mask filter showed the largest decrease in removal efficiency (26%). When the mask was soaked in alcohol, the removal efficiency decreased to a greater degree than when soaked in water. The nanofiber mask filter showed the strongest resistance to alcohol among the tested mask filters. During evaluation of mask reusability, the removal efficiency of certified mask filters decreased by 4% over 5 consecutive days (2 hours per day), and that for the uncertified mask filter decreased significantly, by 30% after 5 days.

The Flow Physics of Face Masks

“…It should also be noted that protection can also decrease as the mask ages due to clogging of the mask material. Reductions of FE of as much as 30% over 10 hours were observed by Lee et al (2022), although this was for uncertified masks (certified masks exhibited only 4% FE reductions). Numerical simulations by Dbouk & Drikakis (2020) also demonstrated this clogging behavior.…”

Performance Comparison among KN95-Certified Face Masks by Classical Techniques and Innovative Test

“…The most common application is to provide both protection to the wearer and to nearby persons from the wearer (patients with COVID-19 may be asymptomatic but still contagious). Facial masks reduce the number of diseasecarrying particulates that infected people exhale but also play a significant role in preventing PM from entering the human respiratory system [16]. Recent studies suggest that wearing face masks blunts the growth of the epidemic curve [17,18], such that some experts claim that universal mask use in public (95% mask use) could be enough to amend the worst effects of epidemic reappearances in many states [19].…”

“…Particle removal efficiency is mainly dependent on particle size and velocity, and the removal mechanism is related to impaction, diffusion, settling, and electrostatic attraction. Breathing resistance is associated with a pressure drop as the air passes through the mask, and can be affected by air velocity, particle loading, particle type (hygroscopic or non-hygroscopic), and relative humidity (RH) [16].…”