If we're truly going to manage indoor environments for occupant health, we need to extend our understanding and management of IAQ to encompass more than the number of microbes in the air.
IAQ strategies to limit indoor exposure to harmful constituents have been revisited in light of heightened concern about infection control brought on by COVID-19. The goals of these efforts are, understandably, to protect occupants from infectious microbes, such as SARS-CoV-2, that are transmitted through the airborne environment.
A foundational tool to manage airborne viral transmission is the Wells-Riley equation, which was developed in 1974 following an outbreak of measles in an elementary school. Based on the concept of a ‘quantum of infection,’ this model predicts the number of infectious droplet nuclei required to infect 1-1e (i.e., 63.2%) of susceptible persons in an enclosed space.