Radon Basics for Washington Homeowners

Radon is a naturally occurring radioactive gas that seeps from the ground into homes, and the EPA identifies it as the leading cause of lung cancer among people who have never smoked. Here is the honest local picture: most of the Puget Sound lowland tests lower than the national average, but pockets of elevated radon exist, and the only way to know your house is a test that costs about twenty dollars. This article explains what radon is, what the Washington maps do and do not tell you, and what happens if your number comes back high.

What is radon and how does it get inside?

Radon forms underground as uranium in soil and rock slowly breaks down. Outdoors it disperses instantly and harmlessly. Under a house, it can concentrate. Heated air rising through a home creates gentle suction on the soil below, pulling soil gases in through slab cracks, crawlspace floors, sump pits, utility penetrations, and even well water in some cases. Radon has no smell, no color, and no taste, and unlike carbon monoxide, there is no alarm that beeps. The risk is also different in character: radon is not an acute emergency but a long-term exposure issue, where risk accumulates over years of breathing elevated levels.

How much radon risk do Puget Sound homes really face?

Less than most of the country, on average, and that is worth saying plainly. The EPA maps every county into three zones by predicted average indoor radon. Much of the western Washington lowland falls into the moderate and low zones, and the glacial soils common around the Sound tend to produce lower readings than the national average. Spokane and several other eastern Washington counties, by contrast, sit in the highest zone. Closer to home, the Washington State Department of Health notes elevated pockets on the west side too, including parts of King, Pierce, and Whatcom counties and foothill areas with different geology.

Two cautions keep this honest. First, zone maps describe county averages, not houses. The EPA itself says homes with elevated radon have been found in all three zones, and two neighboring houses can test very differently depending on soil, foundation, and construction. Second, low average risk is not zero risk. The map is a reason not to panic. It is not a reason not to test. Radon is one piece of the larger indoor air quality picture in a home, alongside the ventilation and moisture issues this region deals with far more often; our overview of indoor air quality basics for Puget Sound homes puts them side by side.

How do you test for radon?

Testing is cheap, easy, and definitive, which makes radon one of the most fixable home health questions there is:

• Short-term test kits cost roughly 15 to 30 dollars at hardware stores and online. You leave the kit in the lowest lived-in level for 2 to 7 days with windows closed as much as practical, then mail it to a lab.
• Long-term tests stay in place for more than 90 days and average out the big seasonal swings, giving a more reliable picture of annual exposure.
• Digital radon monitors in the 150 to 250 dollar range track levels continuously, which is useful because radon varies day to day and rises in the heating season, when closed-up houses pull more soil gas.

Test in the winter if you can, since heating-season readings tend to run highest. Test again after major remodels, foundation work, or adding a basement bedroom, and retest every few years even if the first result was fine.

What do the numbers mean?

Results come back in picocuries per liter, written pCi/L. The EPA's action level is 4.0 pCi/L: at or above that, fix the home. Between 2 and 4 pCi/L, the EPA says to consider fixing, since no level is perfectly risk-free. Below 2 pCi/L, you are doing better than a large share of American homes and can simply retest every few years. One elevated short-term reading is a reason to run a follow-up test, not to panic. Confirm with a second short-term test or a long-term test before spending money on mitigation.

What does radon mitigation involve?

Here is the reassuring part: radon mitigation is a ventilation problem, and it is a solved one. The standard fix, called sub-slab depressurization, is a sealed pipe through the foundation connected to a small, quiet fan that runs continuously, collecting soil gas from under the house and venting it above the roof before it can enter. Homes over crawlspaces get a variant that seals the ground with a heavy membrane and vents from underneath it. Sealing cracks and improving crawlspace ventilation support the system but rarely solve the problem alone. Installed by a certified radon mitigation contractor, these systems typically cost in the range of 1,500 to 3,000 dollars in this region and reliably bring most homes well under the action level.

To be straightforward about our own role: radon mitigation is a specialty performed by nationally certified radon contractors, and it is not a service Eco sells. We cover it here because radon belongs in any honest conversation about healthy homes, and because the ventilation, crawlspace moisture, and air sealing work we do every day interacts with the same parts of the house. If a mitigation system is installed, keep an eye on its manometer gauge and retest every couple of years to confirm it is still working.

Common questions

My neighbor tested low. Do I still need to test?

Yes. Radon varies house to house, not just neighborhood to neighborhood. Different foundation types, soil pockets, and air pressure behavior mean your reading can differ substantially from the house next door. The test is cheap enough that borrowing your neighbor's number is a false economy.

Is radon a bigger deal in basements?

Levels are usually highest in the lowest level of the home, closest to the soil. That is why you test the lowest level people actually use. A basement bedroom or office deserves testing before anyone sleeps or works down there regularly. Upper floors typically read lower.

Does opening windows fix radon?

Temporarily, yes, and impractically. Ventilating dilutes radon while the windows are open, but levels rebound within hours of closing up, and nobody keeps windows open through a Puget Sound winter. Real mitigation intercepts the gas below the house so it never enters.

Should I test for radon when buying a home?

Yes, and it is standard practice in many transactions. A short-term test during the inspection period costs little, and if levels are high, mitigation is a modest, negotiable repair rather than a reason to walk away from a house you love.

What to do next

Order a radon test kit this week, or pick one up at any hardware store, and run it in the lowest lived-in level of your home. If the result is under 2 pCi/L, put a reminder in your calendar to retest in a few years and move on. If it is elevated, confirm with a follow-up test and contact a certified radon mitigation professional. And if the bigger question on your mind is what you are breathing day to day, that is our territory: Eco's indoor air quality team measures and fixes ventilation, filtration, and humidity problems across the Puget Sound area. Book online or call (206) 970-1031, 6 AM to 6 PM every day.