How to test
How to use a short-term radon test kit in a Denver home
A mail-in kit is the right first test for most Front Range houses you already live in. The steps below follow CDPHE’s short-term instructions and EPA’s Citizen’s Guide. A home sale is stricter: hire a DORA-licensed measurement professional instead of relying on a weekend charcoal kit.
Read the leaflet in the box before you close the house. If the kit’s minimum time is longer than 48 hours, the kit wins. If you cannot keep windows shut, wait for a week when you can.
Closed-house conditions are the part Denver households skip. A mild afternoon with the back door open “just for the dog” is not a closed house. Come and go. Do not park a door open. Leave the furnace fan that recirculates indoor air alone. Turn off a whole-house fan.
When the lab report comes back, read it against 4.0 pCi/L, then decide whether you need a follow-up monitor or a licensed mitigator. One number near the line is not the whole story.
- 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.
These steps match the HowTo structured data on this page. Follow the instructions packed with your device if they are stricter.