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During COVID-19 epidemic, people are required to wear masks in workplaces and public places. To many, especially those who engage in manual work, they may feel stuffy or hard to breath after wearing mask for some time. Some may hence pull down their mask or leave their nose uncovered. This will in turn increase risk of virus transmission. Study by the Occupational Safety & Health Council (OSHC) and the Hong Kong Polytechnic University (PolyU) finds that if manual workers and people who exercise wear high breathability mask (with Delta P <3), they are less likely to experience shortness of breath and slower to feel fatigue. The body recovery will also be quicker after work or exercise. OSHC suggests users and employers to look for both filtration efficiency as well as breathability (Delta P) when choosing masks.
What is Delta P?
The lower the value of Delta P, the lower the airflow resistance, that means wearers feel more comfortable.
Delta P (i.e. Pressure Difference) is a measure of breathability of a mask, which reflects its airflow resistance. The higher the value of Delta P (e.g. Delta P > 4 or 5), the higher the airflow resistance, that means wearers may need to breathe harder.
Findings of the Study
OSHC commissioned the Department of Rehabilitation Sciences of PolyU to study the impact of different breathability and shape of masks on physiological responses for wearers undergoing work or workouts that are physically demanding during February to October 2021.
The research team simulated manual work tasks in a controlled environment with high humidity and high temperature to examine the effects of ASTM Level 3 masks with different breathability Delta P value on subjects. The findings showed that, in comparison with wearing a high Delta P mask (Delta P~5.3), wearing masks with low Delta P (Delta P~2.7) could reduce the loading on cardiopulmonary system (e.g. heart rate and respiratory rate) and fatigue of manual workers.
The research team simulated manual work tasks in a controlled environment with high humidity and high temperature to examine the effects of ASTM Level 3 masks with different breathability Delta P value on subjects. The findings showed that, in comparison with wearing a high Delta P mask (Delta P~5.3), wearing masks with low Delta P (Delta P~2.7) could reduce the loading on cardiopulmonary system (e.g. heart rate and respiratory rate) and fatigue of manual workers.
People who exercise wear high breathability mask (with Delta P <3) are less likely to experience shortness of breath and slower to feel fatigue.
OSHC suggests users and employers to pay attention to both filtration efficiency (BFE, PFE, VFE) and breathability─Delta P value when purchasing masks. There are masks on market that are both with high protective efficacy (reaching ASTM Level 3) and low Delta P (≤3). Such masks afford sufficient protection as well as good breathability at the same time. Wearing a low Delta P mask could reduce workers’ physiological loading during manual work. From disease prevention perspective, wearing masks with low Delta P could reduce the wearers’ tendency to take off or pull down the masks due to discomfort, and thus afford better protection against COVID-19.
Research also found that wearing a 3D mask (or a fish-mouth shape 3D mask) is generally more comfortable than a 2D flat mask. Therefore, OSHC also suggested workers who perform manual work in hot and humid environment to consider using low Delta P 3D masks. However, since 3D masks are generally more expensive, 2D masks with low Delta P are also good choices. OSHC calls on employers to purchase low Delta P masks for employees engaging in manual work, with 3D masks being the ideal type.
Currently, relatively few manufacturers would volunteer information of Delta P on packages of masks. OSHC recommends manufacturers to put breathability as one of the essential parameters when producing masks. They should also print information of Delta P value on the package to provide useful reference for public and employers to make informed purchasing decisions.
Research also found that wearing a 3D mask (or a fish-mouth shape 3D mask) is generally more comfortable than a 2D flat mask. Therefore, OSHC also suggested workers who perform manual work in hot and humid environment to consider using low Delta P 3D masks. However, since 3D masks are generally more expensive, 2D masks with low Delta P are also good choices. OSHC calls on employers to purchase low Delta P masks for employees engaging in manual work, with 3D masks being the ideal type.
Currently, relatively few manufacturers would volunteer information of Delta P on packages of masks. OSHC recommends manufacturers to put breathability as one of the essential parameters when producing masks. They should also print information of Delta P value on the package to provide useful reference for public and employers to make informed purchasing decisions.
