With more workers returning to the workplace, the U.S. Centers for Disease Control and Prevention is recommending that employers adopt a layered approach to reducing exposure to the COVID-19 virus that includes addressing building ventilation.

Improving building ventilation can reduce the spread of disease and lower the risk of exposure, especially when combined with physical distancing, face masks, hand hygiene, and vaccinations, the CDC says.

It’s already known that viral particles spread between people more readily indoors than outdoors, where the concentration is often lower and even a light wind can quickly reduce them.

Good ventilation strategies can reduce viral particle concentrations indoors because the lower the concentration, the less likely viral particles can be inhaled, have contact with eyes, nose and mouth, or land on surfaces.

Delivery Dilution

In most cases, the CDC says, reoccupying a building during the COVID-19 pandemic should not require a new ventilation system.

But the agency notes that system upgrades and improvements can increase the delivery of clean air and dilute potential contaminants.

Building owners should consult experienced professionals when considering changes to HVAC systems and equipment.

Buildings that supplied healthy, code-compliant indoor air quality before the pandemic can be improved for pandemic occupancy using less costly interventions.


Steps that can help reduce airborne virus particle concentrations include:

  • Opening outdoor air dampers beyond minimum settings to reduce or eliminate HVAC air recirculation
  • Opening windows and doors, when weather conditions allow, to increase outdoor air flow 
  • Using fans to supplement open windows
  • Checking ventilation systems to ensure proper operation and acceptable indoor air quality for current occupancy of each space
  • Rebalancing or adjusting HVAC systems to increase total airflow to occupied spaces when possible
  • Turning off any demand-controlled ventilation controls that reduce air supply based on occupancy or temperature during occupied hours
  • Increasing air filtration to as high as possible without significantly reducing design airflow 
  • Ensuring air filters are properly sized and used within recommended service life
  • Inspecting filter housing and racks to ensure appropriate filter fit and minimize air that flows around, instead of through, the filter
  • Ensuring restroom exhaust fans are operating at full capacity when the building is occupied
  • Inspecting and maintaining exhaust ventilation systems in kitchens and cooking areas
  • Considering portable high-efficiency particulate air fan/filtration systems to enhance air cleaning, especially in higher risk areas such as a nurse’s office
  • Using ultraviolet germicidal irradiation as a supplemental treatment

For more information, contact CBIA’s Phillip Montgomery (860.244.1982).