Efficacy of universal masking for source control and personal protection from simulated cough and exhaled aerosols in a room

Leave a Reply

You must be logged in to view and post comments.

Face masks reduce the expulsion of respiratory aerosols produced during coughs and exhalations (“source control”). Factors such as the directions in which people are facing (orientation) and separation distance also affect aerosol dispersion. However, it is not clear how the combined effects of masking, orientation, and distance affect the exposure of individuals to respiratory aerosols in indoor spaces. We placed a respiratory aerosol simulator (“source”) and a breathing simulator (“recipient”) in a 3 m 3 m chamber and measured aerosol concentrations for different combinations of masking, orientation, and separation distance. When the simulators were front-to-front during coughing, masks reduced the 15-min mean aerosol concentration at the recipient by 92% at 0.9 and 1.8 m separation. When the simulators were side-by- side, masks reduced the concentration by 81% at 0.9 m and 78% at 1.8 m. During breathing, masks reduced the aerosol concentration by 66% when front-to-front and 76% when side-by- side at 0.9 m. Similar results were seen at 1.8 m. When the simulators were unmasked, changing the orientations from front-to-front to side-by-side reduced the cough aerosol concentration by 59% at 0.9 m and 60% at 1.8 m. When both simulators were masked, changing the orientations did not significantly change the concentration at either distance during coughing or breathing. Increasing the distance between the simulators from 0.9 m to 1.8 m during coughing reduced the aerosol concentration by 25% when no masks were worn but had little effect when both simulators were masked. During breathing, when neither simulator was masked, increasing the separation reduced the concentration by 13%, which approached significance, while the change was not significant when both source and recipient were masked. Our results show that universal masking reduces exposure to respiratory aerosol particles regardless of the orien- tation and separation distance between the source and recipient.

Resources cited in this publication

Anderson EL, Turnham P, Griffin JR, Clarke CC. 2020. Consideration of the aerosol transmission for COVID-19 and public health. Risk Anal. 40(5):902–907. doi:10.1111/ risa.13500

Asadi S, Cappa CD, Barreda S, Wexler AS, Bouvier NM, Ristenpart WD. 2020. Efficacy of masks and face cover- ings in controlling outward aerosol particle emission from expiratory activities. Sci Rep. 10(1):15665. doi:10.


Bahl P, Doolan C, de Silva C, Chughtai AA, Bourouiba L, MacIntyre CR 2020. Airborne or droplet precautions for health workers treating COVID-19? J Infect Dis. doi:10. 1093/infdis/jiaa189

Bergman MS, Zhuang Z, Hanson D, Heimbuch BK, McDonald MJ, Palmiero AJ, Shaffer RE, Harnish D, Husband M, Wander JD. 2014. Development of an advanced respirator fit-test headform. J Occup Environ Hyg. 11(2):117–125. doi:10.1080/15459624.2013.816434

Bourouiba L, Dehandschoewercker E, Bush John WM. 2014. Violent expiratory events: on coughing and sneez- ing. J Fluid Mech. 745:537–563. doi:10.1-017/jfm.2014.88

Brooks JT, Beezhold DH, Noti JD, Coyle JP, Derk RC, Blachere FM, Lindsley WG. 2021. Maximizing fit for cloth and medical procedure masks to improve perform- ance and reduce SARS-CoV-2 transmission and exposure, 2021. MMWR Morb Mortal Wkly Rep. 70(7):254–257. doi:10.15585/mmwr.mm7007e1

CDC. 2020a. How COVID-19 spreads. Atlanta (GA): Centers for Disease Control and Prevention; [accessed 2020 Oct 30]. https://www.cdc.gov/coronavirus/2019- ncov/prepare/transmission.html.

CDC. 2020b. Scientific brief: community use of cloth masks to control the spread of SARS-CoV-2. Atlanta (GA): Centers for Disease Control annd Prevention; [accessed 2021 May 27]. https://www.cdc.gov/coronavirus/2019- ncov/more/masking-science-sars-cov2.html.

Davies A, Thompson KA, Giri K, Kafatos G, Walker J, Bennett A. 2013. Testing the efficacy of homemade masks: would they protect in an influenza pandemic? Disaster Med Public Health Prep. 7(4):413–418. doi:10. 1017/dmp.2013.43

Fennelly KP. 2020. Particle sizes of infectious aerosols: implications for infection control. Lancet Respir Med. 8(9):914–924. doi:10.1016/S2213-2600(20)30323-4

Gralton J, Tovey E, McLaws ML, Rawlinson WD. 2011. The role of particle size in aerosolised pathogen transmission: a review. J Infect. 62(1):1–13. doi:10.1016/j.jinf.2010.11. 010

Halvorsen T. 1998. Fit testing using size-selected aerosol. Shoreview (MN): TSI. Application Note ITI-062.

Hamner L, Dubbel P, Capron I, Ross A, Jordan A, Lee J, Lynn J, Ball A, Narwal S, Russell S, et al. 2020. High SARS-CoV-2 attack rate following exposure at a choir practice – Skagit County, Washington, March 2020. MMWR Morb Mortal Wkly Rep. 69(19):606–610. doi:10. 15585/mmwr.mm6919e6

Han H-S, Prell M. 2010. Penetration of N95 filtering face- piece respirators by charged and charge-neutralized nano- particles. Shoreview (MN): TSI. Application Note RFT- 007 (US).

Honein MA, Christie A, Rose DA, Brooks JT, Meaney- Delman D, Cohn A, Sauber-Schatz EK, Walker A, McDonald LC, Liburd LC, et al. 2020. Summary of guid- ance for public health strategies to address high levels of community transmission of SARS-CoV-2 and related deaths, December 2020. MMWR Morb Mortal Wkly Rep. 69(49):1860–1867. doi:10.15585/mmwr.mm6949e2

Howard J, Huang A, Li Z, Tufekci Z, Zdimal V, van der Westhuizen HM, von Delft A, Price A, Fridman L, Tang

LH, et al. 2021. An evidence review of face masks against COVID-19. Proc Natl Acad Sci USA. 118(4): e2014564118. doi:10.1073/pnas.2014564118

ISO. 2015. Respiratory protective devices – human factors – Part 1: metabolic rates and respiratory flow rates. ISO/TS 16976-1:2015. Geneva (Switzerland): International Organization for Standardization.

ISO. 2010. Respiratory protective devices — human factors — Part 2: anthropometrics. ISO/TS 16976-2:2010(E). Geneva (Switzerland): International Organization for Standardization.

Janssen L, McKay R. 2017. Respirator performance termin- ology. J Occup Environ Hyg. 14(12):D181–D183. doi:10. 1080/15459624.2017.1359018

Joo H, Miller GF, Sunshine G, Gakh M, Pike J, Havers FP, Kim L, Weber R, Dugmeoglu S, Watson C, et al. 2021. Decline in COVID-19 hospitalization growth rates associ- ated with statewide mask mandates – 10 states, March- October 2020. MMWR Morb Mortal Wkly Rep. 70(6): 212–216. doi:10.15585/mmwr.mm7006e2

Kuznetsova A, Brockhoff PB, Christensen RHB. 2017. lmerTest package: tests in linear mixed effects models. J Stat Soft. 82(13):26. doi:10.18637/jss.v082.i13

Lavezzo E, Franchin E, Ciavarella C, Cuomo-Dannenburg G, Barzon L, Del Vecchio C, Rossi L, Manganelli R, Loregian A, Navarin N, et al. 2020. Suppression of a SARS-CoV-2 outbreak in the Italian municipality of Vo’. Nature. 584(7821):425–429. doi:10.1038/s41586-020- 2488-1

Lawrence RB, Duling MG, Calvert CA, Coffey CC. 2006. Comparison of performance of three different types of respiratory protection devices. J Occup Environ Hyg. 3(9):465–474. doi:10.1080/15459620600829211

Lenth RV. 2016. Least-squares means: the R package lsmeans. J Stat Soft. 69(1):33. doi:10.18637/jss.v069.i01

Leung NHL, Chu DKW, Shiu EYC, Chan KH, McDevitt JJ, Hau BJP, Yen HL, Li Y, Ip DKM, Peiris JSM, et al. 2020. Respiratory virus shedding in exhaled breath and efficacy of face masks. Nat Med. 26(5):676–680. doi:10.1038/ s41591-020-0843-2

Lindsley WG, Blachere FM, Beezhold DH, Law BF, Derk RC, Hettick JM, Woodfork K, Goldsmith WT, Harris JR, Duling MG, et al. 2021. A comparison of performance metrics for cloth masks as source control devices for simulated cough and exhalation aerosols. Aerosol Sci Technol. 1–21. doi:10.1080/02786826.2021.1933377

Lindsley WG, Blachere FM, Law BF, Beezhold DH, Noti JD. 2021. Efficacy of face masks, neck gaiters and face shields for reducing the expulsion of simulated cough-generated aerosols. Aerosol Sci Technol. 55(4):449–457. doi:10. 1080/02786826.2020.1862409

Lindsley WG, Noti JD, Blachere FM, Szalajda JV, Beezhold DH. 2014. Efficacy of face shields against cough aerosol droplets from a cough simulator. J Occup Environ Hyg. 11(8):509–518. doi:10.1080/15459624.2013.877591

Lindsley WG, Reynolds JS, Szalajda JV, Noti JD, Beezhold DH. 2013. A cough aerosol simulator for the study of disease transmission by human cough-generated aerosols. Aerosol Sci Technol. 47(8):937–944. doi:10.1080/ 02786826.2013.803019

Lyu W, Wehby GL. 2020. Community use of face masks and COVID-19: evidence from a natural experiment of state mandates in the US. Health Aff (Millwood)). 39(8):

1419–1425. doi:10.1377/hlthaff.2020.00818 MaJ,QiX,ChenH,LiX,ZhangZ,WangH,SunL,

Zhang L, Guo J, Morawska L, et al. 2020. COVID-19 patients in earlier stages exhaled millions of SARS-CoV-2 per hour. Clin Infect Dis. 72(10):e652–e654 doi 10.1093/ cid/ciaa1283

Milton DK, Fabian MP, Cowling BJ, Grantham ML, McDevitt JJ. 2013. Influenza virus aerosols in human exhaled breath: particle size, culturability, and effect of surgical masks. PLoS Pathog. 9(3):e1003205. doi:10.1371/ journal.ppat.1003205

Mitze T, Kosfeld R, Rode J, Walde K. 2020. Face masks considerably reduce COVID-19 cases in Germany. Proc Natl Acad Sci USA. 117(51):32293–32301. doi:10.1073/ pnas.2015954117

Moghadas SM, Fitzpatrick MC, Sah P, Pandey A, Shoukat A, Singer BH, Galvani AP. 2020. The implications of silent transmission for the control of COVID-19 out- breaks. Proc Natl Acad Sci USA. 117(30):17513–17515. doi:10.1073/pnas.2008373117

Morawska L, Milton DK. 2020. It is time to address air- borne transmission of coronavirus disease 2019 (COVID- 19). Clin Infect Dis. 71(9):2311–2313. doi:10.1093/cid/ ciaa939

Oberg T, Brosseau LM. 2008. Surgical mask filter and fit performance. Am J Infect Control. 36(4):276–282. doi:10. 1016/j.ajic.2007.07.008

Pan J, Harb C, Leng W, Marr LC. 2021. Inward and out- ward effectiveness of cloth masks, a surgical mask, and a face shield. Aerosol Sci Technol. 55(6):718–733. doi:10. 1080/02786826.2021.1890687

R Core Team. 2019. R: A language and environment for statistical computing. Vienna (Austria): R Foundation for Statistical Computing; [accessed 2021 Mar 22]. https:// www.R-project.org/.

Rothamer DA, Sanders S, Reindl D, Bertram TH. 2021. Strategies to minimize SARS-CoV-2 transmission in classroom settings: combined impacts of ventilation and mask effective filtration efficiency. Sci Technol Built. doi: 10.1080/23744731.2021.1944665

TSI. 2015. PortaCount Pro 8030 and PortaCount Proþ 8038 respirator fit testers operation and service manual. Shoreview (MN): TSI. P/N 6001868, Revision P.

TSI. 2017. Quantitative respirator fit testing. Fit testing ser- ies 95 respirators with and without N95-CompanionTM Technology. Shoreview (MN): TSI. Application note RFT-024.

Van Dyke ME, Rogers TM, Pevzner E, Satterwhite CL, Shah HB, Beckman WJ, Ahmed F, Hunt DC, Rule J. 2020. Trends in county-level COVID-19 incidence in counties with and without a mask mandate – Kansas, June 1- August 23, 2020. MMWR Morb Mortal Wkly Rep. 69(47):1777–1781. doi:10.15585/mmwr.mm6947e2

Verma S, Dhanak M, Frankenfield J. 2020. Visualizing the effectiveness of face masks in obstructing respiratory jets. Phys Fluids (1994)). 32(6):061708. doi:10.1063/5.0016018

Wang X, Ferro EG, Zhou G, Hashimoto D, Bhatt DL. 2020. Association between universal masking in a health care system and SARS-CoV-2 positivity among health care workers. JAMA. 324(7):703. doi:10.1001/jama.2020.12897

Zhuang Z, Benson S, Viscusi D. 2010. Digital 3-D head- forms with facial features representative of the current US workforce. Ergonomics. 53(5):661–671. doi:10.1080/ 00140130903581656

Leave a Reply

Subscribe to Comments RSS feed