Could air conditioning units help spread COVID-19?

Experts say yes, and suggest precautions
Posted at 6:04 PM, Jul 10, 2020
and last updated 2020-07-10 21:41:52-04

SAN DIEGO (KGTV) — As temperatures warm up, there is some early research suggesting air conditioning units could increase the risk of spreading COVID-19.

One team of researchers swabbed several kinds of air conditioning units and found traces of the virus on one out of every four samples.

One of the authors, University of Oregon professor Dr. Kevin Van Den Wymelenberg, said the research “does give us some pause.”

Air conditioning units bring in little outside air, particularly when temperatures are very hot, posing a risk that viral particles could be recirculated into rooms, Van Den Wymelenberg said.

However, just because the study found traces of the virus in A/C units, it doesn’t prove people can actually get sick from the contaminated air because it’s not yet clear how many viral particles it takes to infect someone, he noted.

“Nobody knows what that minimum threshold is so we need to take as many precautions as possible,” he said.

Dr. Edward Nardell, a professor in the Departments of Environmental Health and Immunology and Infectious Diseases at the Harvard T.H. Chan School of Public Health, said air conditioning units can generate air currents that can carry large particles farther, similar to what researchers found contributed to the spread of the novel coronavirus disease in an air-conditioned restaurant in Guangzhou, China.

"You are not socially distanced as much, but you're re-breathing the same air that someone else just exhaled," Nardell said. "We call it rebreathed air fraction, and if someone is infectious, often asymptomatic, you're going to be rebreathing their small particles."

This week, a group of 239 scientists from 32 countries asked the World Health Organization to update its COVID-19 guidance to reflect that the virus is airborne.

On Thursday, the WHO released updated guidance acknowledging that airborne transmission can’t be ruled out, but stopped short of confirming that the virus spreads through the air.

Instead, the WHO said the virus primarily spreads through droplet transmission, where larger particles come out of an infected person’s mouth, then fall quickly to the ground or onto surfaces. In airborne transmission, the particles stay floating for a long time.

“I think they’re underweighting the importance of this airborne route based on the best available information,” said UC Berkeley Professor Emeritus William Nazaroff, one of the signatories of the letter to the WHO.

He said in a poorly ventilated room, particles might linger for 30 minutes to an hour.

Scientists say one of the best ways to protect yourself is to open windows, to increase the circulation of fresh air.

Scientists say upgraded air filters in AC units and standalone air purifiers could also help.

Germicidal lamps may also be effective, Nardell said. The technology is almost 100 years old, and has been proven effective in protecting against tuberculosis infection.

The lamps, which shine ultraviolet light, are set up to shine horizontally, high up in the room to kill floating pathogens.
Nardell said the technology can be deployed cheaply and easily in a number of settings.

Additional reporting by Lauren Rozyla at WFTS