Indoor Air Quality

Indoor Air Quality


For homes on the Westside of the Cascade Mountains moisture is a common event. Exhausting water vapor after bathing, showering, or cooking is offered homeowners by simply turning on the fan if available. Beyond that homes built in Washington State since 1992 have required a whole house ventilation system. If you live in Central or Eastern Washington your dryer climate may require added humidity during the summer. Suggested humidity levels range from 40% to 60%.

New Homes will have one of the following ventilation systems:

  • Whole House Ventilation Fan- Typically a laundry fan is wired up to a timer to control hours of operation; or
  • Many homes with furnaces are equipped with a fresh air damper again controlled by a timer. When opened the damper allows outdoor air to mix with heated air for distribution; or
  • Air to Air Heat Exchangers- These units transfer heat from exhaust air which is collected by incoming outdoor air.



Want mold? Then don’t ventilate your home, the mold will love it!

Mold Growing in a Petri Dish
Mold Growing in a Petri Dish

Molds can be found almost anywhere; they can grow on virtually any organic substance, as long as moisture and oxygen are present. There are molds that can grow on wood, paper, carpet, foods, and insulation. When excessive moisture accumulates in buildings or on building materials, mold growth will likely occur. If the moisture problem remains undiscovered health problems may occur. It is impossible to eliminate all mold and mold spores in the indoor environment. However, mold growth can be controlled indoors by controlling the humidity level inside the home.

Leave air access to corners and behind couches and beds for air circulation. Keeping these areas open will prevent mold group.


Radon Gas:

A colorless, odorless, naturally occurring, radioactive, inert, gaseous element formed by radioactive decay of radium (Ra) atoms. The atomic number is 86. Although other isotopes of radon occur in nature, radon in indoor air is almost exclusively Rn-222. According to the US EPA, if you have a rating over 4.0 picocuries per liter (pCi/L) you are at risk.

Radon has been found in many Northwest homes. Areas of high levels include the Spokane Valley, Columbia River Gorge, Clark County, and parts of Portland. For these reasons your code official may require a radon stack built into your new home. If your home tests a high level of radon a fan may be added to help exhaust radon from beneath your home.

You can test your home for Radon gas.

  • The National Radon Program Services at Kansas State University offers discounted test kits available to purchase online. You may complete the test kit order form electronically and print it out to mail or fax in. You may download a Radon test kit coupon and mail it in. Go to
  • Some home improvement stores/centers sell radon test kits. Follow the directions on the packaging for the proper placement of the device and where to send the device after the test to get your reading.