COVID-19 has caused more far-ranging, persistent anxiety than any other event in recent history. It has affected our jobs, our living situations, and the way we interact with others, and it’s not done with us yet. Scientists and public health experts are still refining their understanding of the way the virus spreads, but one thing they have determined for certain is that the novel coronavirus spreads through the air—especially within enclosed spaces—and does so far more easily indoors than outdoors or via surface contact.
“Outside is better than inside” has become a refrain among health experts. Depending on the climate where we live and the time of year, most of us can go outside safely on most days. We can maintain social distancing to provide protection from infection. We can wear a mask. But what happens when the weather is just too hot, or air quality too poor, for outdoor activities or open windows? And what about now, as we enter the winter season with temperatures dropping and rain and snow impeding our time to safely open windows and stay outdoors? Among the seemingly endless questions we all have about the virus is how it behaves in more or less enclosed spaces when heating, ventilation, and air conditioning (HVAC) equipment is running to either heat or cool those spaces.
HVAC and COVID-19
Transmission of the novel coronavirus is thought to happen mainly through large droplets expelled from a carrier’s mouth and nose during coughing, sneezing, or talking. Evidence also suggests that at least some cases of COVID-19 occur via airborne transmission. That happens when virus particles contained in smaller droplets don’t quickly settle out and fall to the ground within six feet of the carrier who expelled them, and instead hang in the air and drift around on currents—posing a threat to anyone who happens to walk through one of those currents. Airborne transmission is thought to have been a factor in the coronavirus’s spread among members of a vocal choir in Washington state, through an apartment building in Hong Kong, and in a restaurant in Wuhan, China.
Drawing on what we know about how tuberculosis—another deadly airborne disease—is spread, Dr. Edward Nardel, an infectious disease expert affiliated with Harvard University, suggested recently in an interview for The Harvard Gazette that air conditioning use across the southern U.S. may well be a factor in that region’s surge of COVID-19 cases over the summer. But while expert consensus is that HVAC equipment does have the capacity to spread the virus, questions of what exactly to do about that remain. What precautions can we take to protect ourselves?
One facts-based option to make heating and air conditioning systems safer is to use high-efficiency filters to essentially strain dangerous contaminants out of the air before they get to anyone’s lungs. Peter Catapano, a mechanical engineer with O & S Associates, a national engineering firm based in Hackensack, New Jersey, says the answer lies in high-efficiency particulate air (HEPA) filters, an existing technology currently used in all kinds of medical facilities to filter out many bacterial, fungal, and viral particles.