COVID-19 disease, the disease of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), poses a particular challenge for the indoor environment compared with the outside. New research considers the transmission of COVID-19 via air in poorly ventilated places. Sources of transmission not only relate to the people indoors and how they interact. It could also be that some viral particles enter into indoor environments from the different emission sources aided by environmental factors.
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Other factors also influence the transmission rates, and there is some evidence pointing to the surface stability of SARS-CoV-2 (the current coronavirus of concern) being greater than the stability of SARS-CoV-1 (the ‘SARS’ virus of 2003).
With the point about environmental factors and virus transmission, the new research examines the effect of relative humidity on aerosol transmission (and also accounting for air speed and temperature). Relative humidity refers to the ratio of the partial pressure of water vapor to the equilibrium vapor pressure of water at a given temperature.
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The researchers uncover evidence about the function of relative humidity in airborne transmission of the virus inside. Humidity is an important factor because it affects evaporation kinematics and particle growth. It was found that within dry indoor buildings (defined as areas with a humidity below 40 percent), then the possibility of airborne transmission of the coronavirus were higher when compared to humid places (areas with humidity at 90 percent or more).
Taking into account human comfort and the coronavirus risk, the researchers found that a relative humidity of between 40 and 60 percent was optimal for human health inside. The researchers argue that a minimum relative humidity standard for indoor environments should be put in place.
The research is published in the journal Aerosol and Air Quality Research, titled “An Overview on the Role of Relative Humidity in Airborne Transmission of SARS-CoV-2 in Indoor Environments.”
