Efficacy of face masks, neck gaiters and face shields for reducing the expulsion of simulated cough-generated aerosols

Lindsley, William G.; Blachère, Françoise M.; Law, Brandon F.; Beezhold, Donald H.; Noti, John D.

doi:10.1080/02786826.2020.1862409

Cited by 137 publications

(140 citation statements)

References 48 publications

Supporting

Mentioning

121

Contrasting

Order By: Relevance

“…Our results are also generally consistent with recent unpublished observations examining the material efficiency along with the inward (breathing) and outward (exhaling) particle reduction associated with surgical mask wearing by manikins during simulated breathing 48 . Experiments examining the effectiveness of masking on simulated aerosol emission from coughing using a manikin head yield a somewhat smaller overall efficiency (59%) compared to our observations (90%) 49 . It is possible that this difference results from our experiments having considered mask wearing and coughing by real people, as opposed to simulated coughing using a manikin head, along with potential differences in the aerosol size distributions given the size dependence of the mask efficiency (Fig.…”

Section: Discussioncontrasting

confidence: 91%

Expiratory aerosol particle escape from surgical masks due to imperfect sealing

Cappa

Asadi

Barreda

et al. 2021

Sci Rep

View full text Add to dashboard Cite

Wearing surgical masks or other similar face coverings can reduce the emission of expiratory particles produced via breathing, talking, coughing, or sneezing. Although it is well established that some fraction of the expiratory airflow leaks around the edges of the mask, it is unclear how these leakage airflows affect the overall efficiency with which masks block emission of expiratory aerosol particles. Here, we show experimentally that the aerosol particle concentrations in the leakage airflows around a surgical mask are reduced compared to no mask wearing, with the magnitude of reduction dependent on the direction of escape (out the top, the sides, or the bottom). Because the actual leakage flowrate in each direction is difficult to measure, we use a Monte Carlo approach to estimate flow-corrected particle emission rates for particles having diameters in the range 0.5–20 μm. in all orientations. From these, we derive a flow-weighted overall number-based particle removal efficiency for the mask. The overall mask efficiency, accounting both for air that passes through the mask and for leakage flows, is reduced compared to the through-mask filtration efficiency, from 93 to 70% for talking, but from only 94–90% for coughing. These results demonstrate that leakage flows due to imperfect sealing do decrease mask efficiencies for reducing emission of expiratory particles, but even with such leakage surgical masks provide substantial control.

show abstract

Section: Discussioncontrasting

confidence: 91%

Expiratory aerosol particle escape from surgical masks due to imperfect sealing

Cappa

Asadi

Barreda

et al. 2021

Sci Rep

View full text Add to dashboard Cite

show abstract

“…45 Experiments examining the effectiveness of masking on simulated aerosol emission from coughing using a manikin head yield a somewhat smaller overall efficiency (59%) compared to our observations (90%). 46 It is possible that this difference results from our experiments having considered mask wearing and coughing by real people, as opposed to simulated coughing using a manikin head, along with potential differences in the aerosol size distributions given the size dependence of the mask efficiency (Figure 3). Here we tested only standard surgical masks; it appears likely that other types of masks that have been shown to reduce forward particle emission through the mask, such as N95 masks, would also behave similarly in terms of particle emission through the leakage flows, albeit with differences in the extent of air leakage depending upon fit, but direct experimental measurements are necessary to corroborate this hypothesis.…”

Section: Discussionmentioning

confidence: 98%

Expiratory aerosol particle escape from surgical masks due to imperfect sealing

Cappa

Asadi

Barreda

et al. 2021

Preprint

View full text Add to dashboard Cite

Wearing surgical masks or other similar face coverings can reduce the emission of expiratory particles produced via breathing, talking, coughing, or sneezing. Although it is well established that some fraction of the expiratory airflow leaks around the edges of the mask, it is unclear how these leakage airflows affect the overall mask efficiency at blocking emission of expiratory aerosol particles. Here, we show experimentally that the aerosol particle concentrations in the leakage airflows around a surgical mask are reduced compared to no mask wearing, with the magnitude of reduction dependent on the direction of escape (out the top, the sides, or the bottom). Because the actual leakage flowrate in each direction is difficult to measure, we use a Monte Carlo approach to estimate flow-corrected particle emission rates in all orientations, from which a flow-weighted overall efficiency is derived. The overall mask efficiency, accounting both for air that passes through the mask and for leakage flows, is reduced compared to the through-mask efficiency, from 93% to 70% for talking, but from only 94% to 90% for coughing. These results demonstrate that leakage flows due to imperfect sealing do decrease mask efficiencies for reducing emission of expiratory particles, but even with such leakage surgical masks provide substantial control.

show abstract

“…The efficacy of respirators, medical masks, and cloth masks as source control devices for aerosols produced during coughing and exhalation was determined using a respiratory aerosol source control measurement system described previously (Lindsley et al 2021). The system includes a coughing and breathing aerosol simulator, a manikin headform, an aerosol collection chamber, and a cascade impactor (Figure 1).…”

Section: Methodsmentioning

confidence: 99%

“…The system consists of an aerosol generation system, a bellows and linear motor to produce the simulated coughing and breathing, a pliable skin headform on which the source control device is placed, a 105 liter collection chamber into which the aerosol is coughed or exhaled, and a cascade impactor to separate the aerosol particles by size and collect them. The system is described in more detail in Lindsley et al (2021).…”

Section: Methodsmentioning

confidence: 99%

“…The primary purpose of masks, which includes face masks, neck gaiters, bandanas and other face coverings, is to block the expulsion of infectious droplets and aerosols from the wearer into the environment (called source control) and thereby reduce the exposure of other people to the virus (CDC 2020c). Laboratory studies using manikins and human subjects have shown that cloth face masks can partially block respiratory aerosols produced during coughing, breathing and talking (Asadi et al 2020; Davies et al 2013; Lindsley et al 2021; Pan et al 2020). Wearing medical face masks (i.e., ‘surgical masks’ as defined by the U.S. Food and Drug Administration (FDA 2004)) reduces the dispersion of potentially infectious aerosols from patients with respiratory infections (Leung et al 2020; Milton et al 2013).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A comparison of performance metrics for cloth face masks as source control devices for simulated cough and exhalation aerosols

Lindsley¹,

Blachère²,

Beezhold³

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

Universal mask wearing is recommended by the Centers for Disease Control and Prevention to help control the spread of COVID-19. Masks reduce the expulsion of respiratory aerosols (called source control) and offer some protection to the wearer. However, masks vary greatly in their designs and construction materials, and it is not clear which are most effective. Our study tested 15 reusable cloth masks (which included face masks, neck gaiters, and bandanas), two medical masks, and two N95 filtering facepiece respirators as source control devices for aerosols <7 μm produced during simulated coughing and exhalation. These measurements were compared with the mask filtration efficiencies, airflow resistances, and fit factors. The source control collection efficiencies for the cloth masks ranged from 17% to 71% for coughing and 35% to 66% for exhalation. The filtration efficiencies of the cloth masks ranged from 1.4% to 98%, while the fit factors were 1.3 to 7.4 on an elastomeric manikin headform and 1.0 to 4.0 on human test subjects. The correlation coefficients between the source control efficacies and the other performance metrics ranged from 0.31 to 0.66 and were significant in all but one case. However, none of the alternative metrics were strong predictors of the source control performance of cloth masks. Our results suggest that a better understanding of the relationships between source control performance and metrics like filtration efficiency, airflow resistance, and fit factor are needed to develop simple methods to estimate the effectiveness of masks as source control devices for respiratory aerosols.

show abstract

Efficacy of face masks, neck gaiters and face shields for reducing the expulsion of simulated cough-generated aerosols

Cited by 137 publications

References 48 publications

Expiratory aerosol particle escape from surgical masks due to imperfect sealing

Expiratory aerosol particle escape from surgical masks due to imperfect sealing

Expiratory aerosol particle escape from surgical masks due to imperfect sealing

A comparison of performance metrics for cloth face masks as source control devices for simulated cough and exhalation aerosols

Contact Info

Product

Resources

About