Can Air Conditioning Spread COVID-19?

Summer is coming and lockdown orders are being lifted, people are wondering: Can air conditioning spread COVID-19 droplets, like an office, restaurant, or a movie theater?

Early research may prove these concerns. A recent study, published in Emerging Infectious Diseasesfound that nine people in Wuhan, China (the first epicenter of the new coronavirus outbreak) were infected with the virus simply by sitting near an air conditioning vent in a restaurant. According to researchers, the virus was spread by one asymptomatic diner who sat at a table in front of the AC unit. Four people at the table later tested positive for COVID-19, as did five people at neighboring tables. 

When it comes to the Wuhan restaurant study, it’s important to take into account that it had a small sample size and didn’t replicate conditions in a lab. “I don’t necessarily think that this study is representative of transmission risk,” infectious disease expert Amesh A. Adalja, MD, senior scholar at the Johns Hopkins Center for Health Security in Maryland, tells Health. “However, it is important to be mindful of air flow patterns, especially if they are strong and create a jet stream for droplets.” 

It helps to understand a little about droplets—the particles (containing mostly water, but also any pathogens our bodies may be infected with, such as the coronavirus) that we expel when we breathe, talk, cough and sneeze. A single cough releases about 3,000 droplets, while a single sneeze can release about 30,000, so one sneeze will spread fast in a room. 

Bromage believes that indoor spaces with ventilation systems and lots of people (such as the restaurant in the Wuhan study) are concerning from a transmission standpoint. And Butte agrees that air conditioning can definitely make droplets containing infectious virus particles spread farther. Remember, while air conditioning might make a room feel fresher on a warm day, it’s simply recycled existing air.  

So should we all be ditching our air conditioning systems until the threat of COVID-19 has passed? You should not. Air conditioning in your own home is far less risky than AC in a busy public place, if you’ve been practicing social distancing measures and following all other recommendations regarding hygiene. If you haven’t had a stream of people in and out of your home, the only droplets that could be spread by air conditioning are those from you and whoever you’ve been in lockdown with.

As for air conditioned offices, malls, and restaurants, know that there is a risk, but most experts are not saying that you should refrain from venturing into public places. As lockdown eases, spending time in any public indoor space requires a certain level of risk assessment. If you do go to a restaurant or any other busy place with air conditioning, continue to practice social distancing, be vigilant about hand-washing and not touching your face, wear a mask and, as always, stay home if you feel sick or have COVID-19 symptoms.