Does Air Conditioning Spread Coronavirus? We Asked an Expert
As the days heat up and summer draws nearer, you'll need to keep your home cool—safely.
As scientists and health experts race to better understand COVID-19, new questions arise about what each of us can do to keep safe. How long does the coronavirus stay on certain surfaces? Is it airborne? Will there be a second wave? And now, a new report from the Centers for Disease Control and Prevention (CDC) has linked an outbreak in a China restaurant to its air conditioning unit. As the days heat up and summer draws nearer, should you be worried that your own air conditioning can spread coronavirus?
According to the CDC, a restaurant in Guangzhou, China, was the source of an outbreak affecting 10 people from three different families who dined there on Jan. 23. One person in a four-person family was carrying the virus, although they did not experience symptoms until after that date. But COVID-19 is a disease spread through droplet transmission, and large droplets only remain in the air for a short time and generally travel less than one meter. As the affected families were sitting farther apart than that, the CDC determined that another factor assisted the spread: air conditioning.
The CDC determined that because the air outlet and return air inlet for the restaurant's central air conditioner was located above the infected area, the droplets were most likely transmitted by that ventilation. It's a scary prospect, but what does it mean in practice? We asked an expert what precautions you should be taking. And for more health advice, check out 7 Silent Symptoms of Coronavirus Seniors Need to Know.
How safe is it to use central air conditioning in your home right now?
Qingyan Chen, PhD, a Purdue University professor researching virus transmission through ventilation, says that there is reason to be wary.
"Small droplets can be airborne. Although small droplets carry far less virus than large ones, they could be transferred by air conditioning systems," he explains. "Since most air conditioning systems cannot filter out very small droplets—so the droplets could be recirculated back to indoor spaces—one should be concerned about the use of air conditioning systems."
When it comes to your own home, Chen says you shouldn't be too concerned unless a family member already has coronavirus or is suspected of having it. If they are, he recommends opening windows to get "maximum natural ventilation" instead of blasting your air conditioner.
"If you have one patient or have someone quarantined in a room, please seal the air return inlet in the room," he recommends. "This would prevent the air that may contain coronavirus being recirculated back to the central air conditioning system."
What's safer: central air conditioning or window units?
Since window units only provide air for one indoor space, they would not lead to cross contamination, according to Chen.
"In this COVID-19 season, a window unit is safer," he says.
If you live alone in a residential home, you should be fine running either form of AC. (Provided that you keep practicing proper social distancing through not inviting others into your living space.) If you live in an apartment building that uses central air, you may want to speak to your landlord about what type of system it is. Dedicated outdoor air systems heat and cool spaces using air from outside of the building instead of recirculating, so they are less likely to transmit coronavirus.
As long as you can stay comfortable without it, however, it's safest to keep your AC off completely.
"If the temperature keeps increasing, one can open a window at night to cool the room and close the window in daytime. This could keep the room air temperature low," Chen recommends. "Using a ceiling fan or table fan would also help to cool off." For more tips, check out 15 Ways to Keep Your Home Cool Without Central Air.
Should you clean your air conditioner to help prevent coronavirus spread?
Contrary to what you may have assumed, cleaning your air conditioner right now could be a mistake.
Chen recommends waiting to replace filters in air conditioning units until the COVID-19 pandemic is over, especially since the filter itself could have the virus on it.
"In fact, an older filter has a higher filtration efficiency than a new one, so you should be safe [without replacing it]," he says. "The only downside is that you may get a little bit less air or use a little more energy [to power it]."
Is it safe to visit a reopened restaurant that uses air conditioning?
Some states, such as Georgia, are allowing eateries to reopen. But Chen advises against rushing out for a meal, as "restaurants are one of the most dangerous places" when it comes to risk of infection.
"Most restaurants use mixing ventilation, in which air conditioning systems try to stir room air as much as possible," he explains. "Thus, droplets in restaurants would be uniformly distributed. That is not a great scenario."
Chen says it would take a major "retrofit" to make dine-in restaurants safe to visit before the pandemic is completely controlled. Installing the relatively less risky "underfloor air distribution or displacement ventilation" would take a considerable amount of time and money.
If you do decide to dine out, Chen advises that you patronize restaurants where you can eat outside while observing social distancing to lessen the risk of contracting the disease from another diner. For more coronavirus answers, check out 21 Coronavirus Myths You Need to Stop Believing, According to Doctors.