Row of air conditioning units

Experts don’t yet fully understand the role that HVAC systems play in transmitting COVID-19 indoors. 

The CDC concluded that the ventilation system contributed to the transmission of COVID-19 in an air-conditioned restaurant in Guangzhou, China. 

Most experts agree that a state-of-the-art, modern HVAC system that exchanges outdoor air for indoor air and has excellent filtration reduces the risk of spreading COVID-19. 

To reduce risk in older buildings with ventilation systems that recirculate air:

  • Open windows

  • Use portable air purifiers with HEPA filters

  • Use filters with a Minimum Efficiency Reporting Value (MERV) rating of 13 or higher in the building’s HVAC system

ASHRAE Guidance

The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) has developed guidance and reopening recommendations. They focus on large buildings with complex HVAC systems, like healthcare facilities. According to ASHRAE, transmission of the virus through the air is likely enough that airborne exposure should be controlled. 

The CDC recommends combining these guidelines with everyday preventative measures like physical distancing, wearing face coverings, and hand washing. Businesses may want to implement flexible scheduling and sick leave policies for staff and health checks for staff and visitors. To learn more, visit the CDC’s Interim Guidance for Businesses and Employers page.

Guidance for Reopening Office Buildings

If you are resuming business operations after a long closure the following is recommended:

  • Create a COVID-19 health and safety plan.

  • Have a qualified HVAC expert evaluate the ventilation system. For HVAC systems that have been shut down or on setback, review the new construction start-up guidance provided by ASHRAE. 

  • Increase the circulation of outdoor air as much as possible by opening windows and doors, and using fans. Do not open windows and doors if doing so poses a safety or health risk (including allowing carbon monoxide, molds, or pollens into the building).

  • Check for issues associated with long-term closure such as mold growth, rodents or pests or issues with stagnant water systems

For more COVID-19 guidance pertaining to office buildings, visit the CDC’s COVID-19 Employer Information for Office Buildings page.