American Association for Aerosol Research - Abstract Submission

AAAR 38th Annual Conference
October 5 - October 9, 2020

Virtual Conference

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Assessing the Effectiveness of Using Face Coverings to Mitigate the Transport of Particles Generated from Coughing

LIQIAO LI, Muchuan Niu, Yifang Zhu, University of California, Los Angeles

     Abstract Number: 190
     Working Group: The Role of Aerosol Science in the Understanding of the Spread and Control of COVID-19 and Other Infectious Diseases

Abstract
Respiratory droplets produced by coughing within a close range of about 6 feet is one of the main routes of human to human transmission of SARS-CoV-2 virus during the COVID-19 pandemic. This work investigated the effectiveness of different face coverings to mitigate cough particles at 1ft, 3ft, and 6ft away from the coughing source in a 138 m3 laboratory room. We measured particle number concentration (PNC) and particle size distribution under ten conditions: (1) no face covering; (2) white cotton mask; (3) black cloth mask; (4) surgical mask; (5) N95 mask; (6) face shield; (7) face shield + white cotton mask; (8) face shield + black cloth mask; (9) face shield + surgical mask; (10) KN95 mask. Without any face covering, the average of the background-subtracted peak PNC measured during coughing could reach 123 ± 90 #/cm3 at 1 ft and decrease to a near-background level within 2-4 seconds. At 1 ft, black cloth mask and face shield reduced the PNC to 29% and 68%, respectively, of those without face coverings. When the sampling location moved from 1 ft to 3 ft, the PNC was reduced to 27% without face coverings, 16% with black cloth mask, and 21% with face shield only, respectively. At all other conditions, the PNC was reduced to < 15% of what was measured at 1 ft without face coverings. About 99% of the cough droplets were less than 2.46 µm. The average mode size was 0.59±0.06 µm. Surgical mask, N95 mask, and KN95 mask by itself offer good protection and substantially reduced the cough particles to < 7%. Face shield and black cloth mask by itself does not offer sufficient protection. Nevertheless, wearing any type of face masks would help reduce the transport of cough particles.