The American Society for Microbiology has recently addressed the issue of COVID-19 transmission in the “built environment”, defined as the buildings, automobiles and other indoor settings in which most humans spend more than 90 percent of their daily lives.2 There are several major transmission vectors that promote infection in these built environments, the report says, including occupant density, the amount of social activity and interaction, and human contact with abiotic surfaces. The cruise ship industry, nursing homes and prisons have taught us about the risk of transmission from settings where these vectors intersect. However, we also have learned that proper hand-washing and social distancing work to reduce transmission. 

Alongside these primary mitigants, HVAC systems work in a built environment to supply comfortable, clean, recaptured air, mix in healthy levels of fresh air, and contain or exhaust contaminants. Air delivery systems can reduce the transmission of viruses through inline filtration, something HVAC professionals are capable of assessing. 

Air-conditioning systems are also critical in maintaining healthy humidity levels. “Maintaining a RH (relative humidity) between 40% and 60% indoors may help to limit the spread and survival of SARS-CoV-2 within the BE,” the ASM suggests, “while minimizing the risk of mold growth and maintaining hydrated and intact mucosal barriers of human occupants.”

The Centers for Disease Control (CDC) echoes these findings, saying that employers can decrease the spread of COVID-19 by maintaining a healthy work environment. “Consider improving and engineering controls using the building ventilation system,” the CDC suggests, including increased ventilation rates and increased percentage of outdoor air circulating through the system.

Well before COVID-19, the Healthy Building Movement had begun to measure and improve air quality in the built environment to improve productivity and health. Of the nine foundations for a healthy building, five relate to HVAC, including air quality, ventilation, thermal health, moisture, dust and pests. “There’s just no reason anymore to economize on airflow and filtration,” Harvard Business School’s John Macomber says. “It’s a cheap way to help people be healthier.”