2021 April

(2020). The coronavirus pandemic and aerosols: Does COVID-19 transmit via expiratory particles? Aerosol Science and Technology: Vol. 54, No. 6, pp. 635-638.

Tasks ASHRAE plans

"The total airborne mass fraction was between 2.7% and 32.2% of the mass emitted from the bottle, depending on the product. Between 0.0001% and 0.01% of the total airborne mass fraction consisted of residual particles. However, these particles had a mass median aerodynamic diameter between 1.9 µm and 3.7 µm, constituting a total respiratory deposition of up to 77%...Thus, the use of cleaning sprays can result in chemical airway exposure, with particles in the relevant size range for both nasal and alveolar deposition"

Includes analyses of effects of humidity on transmission

The update officially acknowledges growing evidence that under certain conditions, people farther than six feet apart can become infected by tiny droplets and particles that float in the air for minutes and hours, and that they play a role in the pandemic.

"People infected with SARS-CoV-2 exhaled 1,000–100,000 copies per minute of viral RNA, a marker of the pathogen’s presence. Because the volunteers simply breathed out, the viral RNA was probably carried in aerosols." "When researchers created aerosols of the new coronavirus, the aerosols remained infectious for at least 16 hours, and had greater infectivity than did those of the coronaviruses SARS-CoV and MERS-CoV." "No amount of ventilation could have reduced the risk to an acceptable level for the two-and-a-half-hour rehearsal, she says." "SARS-CoV-2 in mock saliva aerosols lost 90% of its viability in 6 minutes of exposure to summer sunlight, compared with 125 minutes in darkness."