Wearing time and respiratory volume affect the filtration efficiency of masks against aerosols at different sizes

Abstract

Face masks are critical in preventing the spread of respiratory infections including coronavirus disease 2019 (COVID-19). Different types of masks have distinct filtration efficiencies (FEs) with differential costs and supplies. Here we reported the impact of breathing volume and wearing time on the inward and outward FEs of four different mask types (N95, surgical, single-use, and cloth masks) against various sizes of aerosols. Specifically 1) Mask type was an important factor affecting the FEs. The FEs of N95 and surgical mask were better than those of single-use mask and cloth mask; 2) As particle size decreased, the FEs tended to reduce. The trend was significantly observed in FEs of aerosols with particle size < ; 3) After wearing N95 and surgical masks for 0, 2, 4, and 8 h, their FEs (%) maintained from 95.75 ± 0.09 to 100 ± 0 range. While a significant decrease in FEs were noticed for single-use masks worn for 8 h and cloth masks worn >2 h under deep breathing (30 L/min); 4) Both inward and outward FEs of N95 and surgical masks were similar, while the outward FEs of single-use and cloth masks were higher than their inward FEs; 5) The FEs under deep breathing was significantly lower than normal breathing with aerosol particle size ¡1 m. In conclusion, our results revealed that masks have a critical role in preventing the spread of aerosol particles by filtering inhalation, and FEs significantly decreased with the increasing of respiratory volume and wearing time. Deep breathing may cause increasing humidity and hence decrease FEs by increasing the airflow pressure. With the increase of wearing time, the adsorption capacity of the filter material tends to be saturated, which may reduce FEs Findings may be used to provide information for policies regarding the proper use of masks for general public in current and future pandemics.

Assessment of Different Experimental Setups to Determine Viral Filtration Efficiency of Face Masks

“…Similar observations on the FEs of different masks were made by other groups, which found high FEs (either BFE, VFE, or PFE) in surgical masks and respirators, while cloth masks had different FEs, which in some cases were quite high, above 90% [ 23 , 24 , 25 , 36 ]. Caution should be exercised in interpreting these results because the fit of masks is usually not taken into account when FE is determined, and therefore the protection provided by the masks does not necessarily correspond to the measured FE.…”

Assessment of different experimental setups to determine viral filtration efficiency of face masks

“…Similar observations on the FEs of different masks were made by other groups, which found high FEs (either BFE, VFE, or particle ltration e ciency, PFE) in surgical masks and respirators, while cloth masks had different FEs, which in some cases were quite high, above 90% [18][19][20]28 . Caution should be exercised in interpreting these results, because the t of masks is usually not taken into account when FE is determined, and therefore the protection provided by the masks does not necessarily correspond to the measured FE.…”

Integration of IoT Sensors to Determine Life Expectancy of Face Masks

“…Mask performance can be categorized into the efficiency of the filtration of a mask and the breathability of a mask [ 11 ]. The filtration efficiency defines how well the filter keeps internal and external aerosol droplets from passing through to the mask wearer [ 12 ]. The breathability of a mask is a measure of how resistant the mask is to inhalation and exhalation.…”

“…Single-use masks are recommended to be safe for up to 4 h of wear, after which the mask may not effectively protect the user [ 10 ]. Experiments conducted on different types of masks suggest that cloth masks may have a safe wearing period of up to 2 h, with single-use masks being protective for up to 8 h without significant reductions in the filtration efficiency [ 12 ].…”