Particle leakage through the exhalation valve on a face mask under flow conditions mimicking human breathing: A critical assessment

Abstract

In today's era of active personal protections against airborne respiratory disease, general interest in the multiphase flow physics underlying face masks is greater than ever. The exhalation valves, installed on some masks to mitigate the breathing resistance, have also received more attention. However, the current certification protocol of evaluating airflow leakage only when suction pressure is applied is insufficient to capture practical aspects (particle penetration or leakage). Here, we experimentally measure two-phase flow across valve-type masks under conditions mimicking actual breathing. During exhalation, a high-speed jet through the valve accelerates the transmission of particles from inside while reasonable protection from external pollutants is achieved during inhalation, which supports the warnings from various public health officials. Based on the mechanism of particle penetration found here, we hope a novel design that both achieves high-efficiency shielding and facilitates easy breathing can be developed.

Quantitatively Visualizing Airborne Disease Transmission Risks of Different Exhalation Activities through CO2 Imaging

“…This may be due to the long duration of a single deep breathing activity and also suggests a high cumulative risk of a single activity. For yawning, it is an assisted activity through the chest, starting from deep in the lungs; 49 thus, there is a period of airflow accumulation before the final mouth opening and exhalation. While for laugh, it is not essentially a single exhalation activity; i.e., a single laughter may include the accumulation of several laughing exhalations.…”

“…This may be due to the long duration of a single deep breathing activity and also suggests a high cumulative risk of a single activity. For yawning, it is an assisted activity through the chest, starting from deep in the lungs; thus, there is a period of airflow accumulation before the final mouth opening and exhalation. While for laugh, it is not essentially a single exhalation activity; i.e., a single laughter may include the accumulation of several laughing exhalations.…”

Optimized mechanism for fast removal of infectious pathogen-laden aerosols in the negative-pressure unit

“…Since the outbreak of SARS-CoV-2, to mitigate the rapid airborne transmission, the public health officials and government organizations have strongly emphasized the use of face masks as a personal hygiene ( Fischer et al, 2020 , Repici et al, 2020 , Kang et al, 2021 ), limitation of the occupancy number in a meeting group ( Jones et al, 2020 ), and the social distancing ( Balachandar et al, 2020 , Chen et al, 2020 ). In Italy, it was reported that the SARS-CoV-2 RNA concentration of air samples measured in various indoor communities (such as the train station, food market, shopping center, and pharmacy) was significantly reduced by the restrictive policies ( Conte et al, 2022 ).…”