COVID-19 Guidance on Ventilation in the Workplace

Current as of 4/3/2023

Risk for spreading COVID-19 is higher:

  • In small rooms, enclosed areas, and tight spaces with little or no ventilation or poorly filtered air.
  • In locations where activities that cause increased respiration (e.g. strenuous work, talking, singing) occur.

Ensuring adequate ventilation throughout the work environment can help to maintain a safe and healthy workplace.

Employers should work with a heating, ventilation, and air conditioning (HVAC) professional to optimize building ventilation and check to ensure the system is fully functional and operating as intended (especially systems previously shut down or operated at reduced capacity).

The following tips can help reduce the risk of exposure to COVID-19:

  • Use HVAC system filters with a Minimum Efficiency Reporting Value (MERV) rating of 13 or higher, where feasible. MERV is a measure of how well filters capture particles. The higher the number, the better the capture of particles. Ninety-percent of particles are captured in filters with a MERV rating of 13.
  • Inspect filters and seals monthly. Eliminate gaps around filters that allow non-filtered air to recirculate. Change filters and clean the system as needed.
  • Bring in as much fresh air as possible by increasing the HVAC system’s outdoor air intake and reducing recirculated air. Demand-controlled ventilation may be adjusted or disabled to ensure maximum outdoor air. Open windows or other sources of fresh air where possible, weather permitting.
  • Be sure exhaust air is not pulled back into the building from HVAC air intakes or open windows.
  • Turn off ceiling fans or adjust them to pull air up rather than down to reduce particle dispersal.
  • Remove or redirect personal fans to prevent blowing air from one worker to another.
  • Consider using portable, high-efficiency particulate air (HEPA) fan/filtration systems to clean air, especially in higher-risk areas like enclosed smaller spaces with little or no ventilation or capability to provide outside air. Avoid use of ionizers or air purifiers that generate ozone, a health hazard itself.
  • When changing filters, wear appropriate personal protective equipment including a respirator with N-95 filters, eye protection (safety glasses, goggles, or face shields), and disposable gloves.
  • Make sure exhaust fans in restrooms are fully functional, operating at maximum capacity, and are set to remain on.
  • Encourage workers to report ventilation issues and other safety and health concerns.

More help from L&I

Free safety and health assistance for employers is available from L&I’s Consultation Program: or

L&I Division of Occupational Safety and Health COVID-19 webpage includes resources from the Centers for Disease Control and Prevention (CDC), the Occupational Safety and Health Administration (OSHA), and the Washington State Department of Health:

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