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COVID-19 is an airborne virus and can spread easily indoors. Information on this page will help explain ways to improve indoor air in our homes, businesses, schools, and other places where people gather indoors.

See also: Indoor air ventilation guide/pamphlet

While we no longer have portable HEPA air cleaners to provide, we are still available to offer free technical assistance to help you improve your ventilation and indoor air quality. To request assistance, please complete this form to the best of your ability. Our staff will respond as soon as possible. If you need help with the form or an interpreter, please contact or 206-477-5166. If you received a portable HEPA air cleaner, watch our video "Using and maintaining your HEPA Air Cleaner for information on setting up and maintaining your cleaner.

Improving Indoor Air at Home: steps to improve your house indoor air quality.

Indoor Air Quality Webinar: information about Indoor Air Quality to keep customers safe.

Three ways to improve indoor air

Increase Air Flow

Introduce more outdoor air to indoor spaces:

  • Open windows and doors to increase the flow of outdoor air into the building.
  • Increase the amount of outdoor air that is pulled in through the Heating, Ventilation, and Cooling (HVAC) system to 100%.
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Clean Indoor Air

Remove pollutants from indoor air by adding air filtration:

  • Improve your HVAC system by having it evaluated by a specialist. Determine if it can handle high efficiency filters (rated MERV 13 or higher) and install those filters if it can.
  • Use portable HEPA air cleaners that provide 99% or higher filtration efficiency down to 0.3 microns.
  • For a low-cost option, use a box fan with a MERV 13 furnace filter attached to the back.
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Kill Germs in the Air Using Upper Room Ultraviolet Germicidal Irradiation

Ultraviolet Germicidal Irradiation (UVGI) systems can kill germs in the air but cannot remove pollutants. Use UVGI in addition to ventilation and air filtration to improve indoor air.

This solution is only intended for specific spaces and not for inside homes. Work with a specialist to see if it is appropriate to be installed in your space.

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These strategies work best when used with mask-wearing, hand-washing, social distancing, and other public health recommendations that reduce the risk of spreading COVID-19.

Indoor Air Ventilation Guide

This guide is for operators of congregate settings, schools and childcare services, restaurants, and retail or other settings where people may gather. It includes strategies that reduce the spread of COVID-19 in their facilities.

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