New study reveals how much worse air conditioning makes the spread of COVID-19

The SARS-CoV-2 coronavirus funding our pandemic is believed to be the least stable in warm temperatures. UV rays in the sun are said to eliminate the virus as quickly as 34 minutes, reducing the chance of transmission that occurs via turbulent aerosols.

As more and more offices and hospitality industries continue to reopen, it’s important to review all of the viable and remote infection risk factors. While suspended in aerosols, viral material can remain active for nearly three hours and can travel as far as 15 feet.

Adding to the dangers of indoor cluster spreading is new research analyzing the ways in which air conditioners can recirculate coronavirus virions inside enclosed areas.

“As people go indoors in hot weather and the rebreathed air fraction goes up, the risk of infection is quite dramatic,” Edward Nardell, an infectious disease expert at Harvard Medical School, told The Harvard Gazette. “The prudent and pragmatic approach is to acknowledge that airborne transmission is happening and put in the controls. If we find out in five years that airborne was 5% of transmission, then OK,” Allen said. “But what if it’s 20% or 30% and we failed to acknowledge it? That’s a problem.”

Although we dramatically increase our chances of getting infected with the virus while indoors, it’s not yet known how much air conditioners are contributing to the likelihood of this outcome-even if it has been concluded to be theoretically possible by various academic systems.

Between January 26 and February 10, 2020, an outbreak of the novel coronavirus in an air-conditioned restaurant in Guangzhou, China, involved three family clusters. Ten people that attended this restaurant later tested positive for COVID-19.

A new paper published in the journal of Emerging  Infectious DIsease posited that droplet transmission was prompted by air-conditioned ventilation in this scenario.

From the report:

“The key factor for infection was the direction of the airflow. Of note, patient B3 was afebrile and 1% of the patients in this outbreak were asymptomatic, providing a potential source of outbreaks among the public (7,8). To prevent spread of COVID-19 in restaurants, we recommend strengthening temperature-monitoring surveillance, increasing the distance between tables, and improving ventilation.

“The airflow direction was consistent with droplet transmission. To prevent the spread of the virus in restaurants, we recommend increasing the distance between tables and improving ventilation.”

The authors made a point to note that they did not perform serologic studies of swab sample–negative asymptomatic family members and other diners to estimate risk for infection. However, they pinpointed a single systematic carrier responsible for spreading the virus to nine other patrons over the course of an evening.

Researchers were so confident of the findings indexed above, many have gone on record to urge Americans to list their due of split -unit air conditioners whenever possible.

The ideal humidity to reduce transmission risk is somewhere between 40% and 60%. Offices should invest in air purifiers given the risk increases in large densely populated buildings.

“Studies by the signatories and other scientists have demonstrated beyond any reasonable doubt that viruses are released during exhalation, talking, and coughing in microdroplets small enough to remain aloft in air and pose a risk of exposure at distances beyond 1 to 2 m from an infected individual (see e.g. [1-4]),”Lidia Morawska 1, and Donald K. Milton wrote in an open letter. “We are concerned that the lack of recognition of the risk of airborne transmission of COVID-19 and the lack of clear recommendations on the control measures against the airborne virus will have significant consequences: people may think that they are fully protected by adhering to the current recommendations, but in fact, additional airborne interventions are needed for further reduction of infection risk.”