How to test your Denver home for radon

Radon is a radioactive gas from uranium breaking down in soil. You cannot see, smell, or taste it. CDPHE calls it the second leading cause of lung cancer after smoking, and EPA ties about 21,000 lung-cancer deaths a year to it. The only way to know your level is a test.

Because the county map is not your result. Denver County is EPA Zone 1, and CDPHE says about half of Colorado tests come in above 4.0 pCi/L. High and low results sit on the same street. Test your Denver home, not the reputation of the block.

4.0 pCi/L is the level where EPA and CDPHE say to fix your home. Between 2 and 4, they say consider it. There is no safe level, and you can usually get your Denver home to 2 or below. EPA’s Citizen’s Guide explains the number.

Start with a short-term kit for a first screen. A long-term test runs 91 days to a year and gives the better yearly average. CDPHE describes both on its testing page. A sale needs a licensed professional and a continuous monitor, not a charcoal kit.

At least 48 hours, after you have kept your Denver home closed for 12 hours. Many charcoal kits run 48 to 120 hours, so follow the package and do not stop early. Write down the start and stop times and mail it within a day.

The lowest level you live in, 2 to 7 feet off the floor, in a room you use. CDPHE says to skip crawl spaces, closets, kitchens, bathrooms, laundry rooms, exterior walls, vents, and direct sun. For a sale, the professional tests the lowest space that could become living area.

Shut windows and exterior doors 12 hours before you test and keep them shut, coming and going as you normally do. You can run heating and cooling, but not a whole-home fan. CDPHE says winter is fine and often easier. Wait out an unusually windy or stormy stretch.

Treat it as a maybe. EPA’s example of a 4.1 average leaves about a 50 percent chance the yearly number is under 4. Watch a continuous monitor for a few weeks, then confirm with a second short test or a long-term test before you hire anyone.

Use a mail-in kit for the first lab number and a monitor to watch a trend near the line. The monitor does not make the mitigation decision. The Airthings links do not apply ARS10-10OFF. After your name and shipping are in the cart, enter the code for 10 percent off. We may earn a commission. American Radon Systems does not install in Denver.

CDPHE offers one free kit per household per year while supplies last, and store kits run about $10 to $50. A licensed measurement runs around $150, and a Colorado mitigation system about $1,000 to $2,000. Order from the testing page. These are CDPHE figures, not a quote.

CDPHE tells buyers to test during inspection with a licensed professional and a continuous monitor, at the lowest level that could become living space. If it is high, the parties negotiate the fix. This is not legal advice. See CDPHE’s testing page.

No. CDPHE and EPA’s Consumer’s Guide say sealing supports a system but cannot stop radon on its own, because sealant ages and no one finds every gap. The reliable fix is a soil-suction system under the slab.

Colorado requires a DORA license to measure or mitigate for someone else. You can run your own kit, but a sale or an unbiased result calls for a licensed professional, around the $150 CDPHE mentions. Verify anyone at the license lookup. This guide does not name companies.

Retest about every two years if you have a system, and after you finish a basement, add on, or tighten your Denver home. CDPHE says you should test even if a system was already there when you bought. A low first result is not permanent.

Yes. You can test the Denver unit you rent. Since August 7, 2023 your landlord must disclose radon information when you sign, under SB23-206. EPA’s tenant guide is the national version. A building-wide fan is your landlord’s call. This is not legal advice.

Yes. EPA says you should test after you move in, even with radon-resistant features. A passive vent without a fan is not proof your level is under 4. Ask the builder what was installed, then test your finished home.

The risks combine. If you smoke and you live with high radon, EPA says your lung-cancer risk is especially high. Fixing your Denver home does not replace quitting, and quitting does not replace a test. See EPA’s health page. This is not medical advice.