Some diseases (including COVID-19, Influenza, and RSV) spread through the air. This happens when people infected with a virus breathe it out. Other people in the room or nearby can then breathe in the virus and become infected.  

The quality of the air inside a building can affect how much a virus builds up indoors. Improving indoor air quality can help lower the amount of virus in the room. Diluting, mixing, and filtering the air are three ways you can improve indoor air quality.

Read the full CDPH Occupational Health - Indoor Air Quality Webpage Summary

Dilute, Mix, and Filter the Air

• Dilute: Draw fresh air in 
  Use a Heating, Ventilation & Air Conditioning (HVAC) system or bring in outside air by opening windows and doors when weather permits. 

• Mix: Move the air flow 
  Move around the air inside a room with fans (ceiling, wall-mounted, or portable), and/or through the vents in your HVAC system.  

• Filter: Clean the air  
  Clean the air by trapping germs through HVAC system filters (MERV 13 rating and higher) and portable air cleaners with high efficiency particulate air (HEPA) filters.  

The infographic below shows two scenarios to enhance indoor air quality by diluting, mixing, and filtering the air. Learn more at: CDPH Occupational Health Branch Improving Indoor Air Quality at Work