COVID-19 Ventilation Guidelines for Businesses

The City of St. Louis Department of Health provides recommendations to mitigation the transmission of the SARS-CoV-2 virus through ventilation system changes.


  • The City of St. Louis Department of Health provides the following guidelines due to changing conditions of the SARS-CoV-2 virus, which causes COVID-19.
  • The following are general guidelines for commercial HVAC systems.

Reduce workforce within business settings as much as possible

  • Permit work from home option to reduce in-person staff
  • Consider different shift work when working from home is not available

Increase outside air ventilation rates

  • Begin running HVAC systems two hours before and continue running for two hours after a building is occupied
  • Open air dampers to reduce or eliminate HVAC air recirculation and allow for an outside air supply per person of 15 cubic feet per minute (CFM)

Adjust HVAC system settings to expand the number of air exchanges within indoor settings

  • Make necessary adjustments to allow for a minimum of six (6) air changes per hour (ACH)

Improve air filtration rates through filter upgrades

  • Use the highest MERV-rated filter available for current HVAC equipment
  • MERV 13 rating is recommended by ASHRAE for COVID-19 mitigation

Add HEPA filter air cleaners

  • Add localized HEPA filter systems in high-traffic areas to reduce air particles

Ensure systems are operating in the most effective modes

  • Set the fan to run in the “on” or “continuous” mode. Refrain from using the “auto” setting.
  • Disable Demand Control Ventilation (DCV), if applicable to the system
  • Enable humidification and economizing, if applicable to the system

Schedule regular service on HVAC systems

  • Perform routine maintenance on HVAC system(s)
  • Consider having systems checked by an HVAC expert


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