Human Research Study of Particulate Propagation Distance From Human Respiratory Function.

Background: Airborne viral pathogens like severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can be encapsulated and transmitted through liquid droplets/aerosols formed during human respiratory events.

Methods: The number and extent of droplets/aerosols at distances between 1 and 6 ft (0.305-1.829 m) for a participant wearing no face covering, a cotton single-layer cloth face covering, and a 3-layer disposable face covering were measured for defined speech and cough events. The data include planar particle imagery to illuminate emissions by a light-sheet and local aerosol/droplet probes taken with phase Doppler interferometry and an aerodynamic particle sizer.

Results: Without face coverings, droplets/aerosols were detected up to a maximum of 1.25 m (4.1ft ± 0.22-0.28 ft) during speech and up to 1.37 m (4.5ft ± 0.19-0.33 ft) while coughing. The cloth face covering reduced maximum axial distances to 0.61 m (2.0 ft ± 0.11-0.15 ft) for speech and to 0.67 m (2.2 ft ± 0.02-0.20 ft) while coughing. Using the disposable face covering, safe distance was reduced further to 0.15 m (0.50 ft ± 0.01-0.03 ft) measured for both emission scenarios. In addition, the use of face coverings was highly effective in reducing the count of expelled aerosols.

Conclusions: The experimental study indicates that 0.914 m (3 ft) physical distancing with face coverings is equally as effective at reducing aerosol/droplet exposure as 1.829 m (6 ft) with no face covering.