Does air conditioning spread the coronavirus? Experts weigh in

It’s hot, with record highs already this month in Colorado, and you want your employees to stay comfortable while they work. That usually means running the air conditioning.

But nothing is playing out like usual this summer. The COVID-19 pandemic has raised new safety concerns, with business owners second-guessing all their regular summer behaviors. You may wonder, is it OK to use air conditioning at work or could it help spread coronavirus?

The experts we spoke with agreed you can run it, if you are careful. Joan Brown, CIH, ARM, an industrial hygienist at Pinnacol, notes that while researchers have raised concerns about air conditioning safety, workplaces that take proper precautions can maintain a healthy work environment using the building ventilation system.

“Supplying fresh outdoor air, increasing outdoor air exchange rates and improving central air filtration are important factors in controlling the spread of the virus,” she says.

Mike Van Dyke, PhD, CIH, associate professor at the Center for Health, Work & Environment at the Colorado School of Public Health, identifies airflow direction (blowing air from one person in the direction of others) as a key to using AC safely.

“This directional air flow could theoretically increase the distance that COVID-containing droplets travel from person to person. Employers should be thinking about airflow direction in how they locate employees in the workplace — this includes both air conditioning (and heating) supply vents and the use of portable fans,” Van Dyke says. “In most commercial buildings, turning off a central air conditioning system would be counterproductive.”

He says there is limited evidence that HVAC systems spread coronavirus. One recent study tied an outbreak in China to air conditioning in a restaurant, and researchers concluded that the most likely cause was droplet transmission. Van Dyke cautions that the research has limitations. “The article that everyone is referencing regarding COVID-19 and air conditioners provides limited evidence due to small numbers and an incomplete evaluation of the air conditioning system,” he says.

The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) has endorsed continued use of air conditioning, saying companies should also consider the risks of not keeping employees cool. A statement on its website says, “Unconditioned spaces can cause thermal stress to people that may be directly life threatening and that may also lower resistance to infection.”

To use your AC safely in the next few months, Brown suggests following these tips from the Centers for Disease Control and Prevention:

  • Increase ventilation rates.
  • Ensure ventilation systems operate properly and provide acceptable indoor air quality for the current occupancy level for each space.
  • Increase outdoor air ventilation, using caution in highly polluted areas. With a lower occupancy level in the building, this increases the effective dilution ventilation per person.
  • Disable demand-controlled ventilation (DCV).
  • Further open minimum outdoor air dampers (as high as 100%) to reduce or eliminate recirculation.
  • Improve central air filtration to the MERV-13 rating or the highest compatible with the filter rack, and seal edges of the filter to limit bypass.
  • Check filters to ensure they are within service life and appropriately installed.
  • Keep systems running longer hours — 24/7 if possible — to enhance air exchanges in the building space.

Research on COVID-19 is evolving quickly, and guidance can change just as fast. To discuss questions about HVAC safety or learn the latest, contact a safety consultant at Pinnacol’s Safety On Call at safetyoncall@pinnacol.com.

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