One-pager
Denver radon test kit, on one page
Reviewed for accuracy against EPA and Colorado Department of Public Health and Environment guidance on September 22, 2026.
Test the house you live in. Denver County is EPA Zone 1, and about half of Colorado homes test over 4.0 pCi/L according to CDPHE. That is not your living room’s number.
Close the house for 12 hours, then run a short-term kit at least 48 hours on the lowest inhabitable level, 2 to 7 feet off the floor. Ship it the day you finish. Read the lab result against 4.0 pCi/L.
Near 4, watch a continuous monitor for a few weeks and confirm with another test before you buy a fan. If it stays at or above 4, hire a DORA-licensed mitigator. Sealing cracks is not a fix by itself.
Free state kits, one per household per year while supplies last, start at CDPHE. This page is education, not a lab report. Full guide: https://denverradontestkit.com/
- 1
Close the house for 12 hours
Shut exterior windows and doors 12 hours before you start, and keep them closed for the whole test. Come and go normally. Do not leave a door standing open. Heating or cooling that recirculates indoor air can run. Do not run a whole-house fan.
- 2
Place the kit 2 to 7 feet up
Use the lowest inhabitable level, even an unfinished basement if that is the level you are checking. Set the kit on a table or shelf 2 to 7 feet above the floor, in an open spot someone uses. Skip crawl spaces, closets, kitchens, laundry rooms, bathrooms, exterior walls, vents, direct sun, and granite tops.
- 3
Leave it at least 48 hours
CDPHE’s minimum is two days. Many short-term kits run 48 to 120 hours. If the package asks for longer than 48 hours, follow the package. Do not stop early.
- 4
Record the times and the serial number
Write the start and stop date and time to the minute. Photograph the kit serial number or barcode so you can register the test and retrieve the lab result.
- 5
Ship the day you finish
Do not wait more than a day to send the kit to the lab named on the device. A kit that sits in a car is not a closed-house test anymore.
- 6
Read the result against 4.0
At or above 4.0 pCi/L, CDPHE and EPA point toward fixing the house after you confirm the result. Near the line, watch with a continuous monitor and run a follow-up test before you hire a mitigator.
Guide: https://denverradontestkit.com/