How to test for radon
Testing is the only way to know the radon level in your home. EPA says homes with elevated radon have been found in every zone, so the map is not a reason to skip the test.
If a health department near you sells a kit, start with the locator. Then follow the instructions in the box. The notes below are the public steps we checked, not a replacement for your kit.
Short-term or long-term
Minnesota's health department says a short-term test usually runs 2 to 7 days and is the right first screen. A long-term test runs at least 90 days and is the better estimate of your yearly average. Colorado's health department describes short-term tests as 48 to 120 hours, after the house has been closed for 12 hours, and long-term tests as 91 days to one year under normal living conditions.
Where to put the kit
MDH says to test the lowest level you use regularly. If you spend more than about 10 hours a week in the basement, test there. For a Minnesota real estate test, MDH says to test the lowest level, such as the basement.
Place the kit at least 20 inches above the floor. Keep it about 1 foot from exterior walls, 3 feet from exterior windows, and away from drafts. Keep it out of kitchens, baths, laundry rooms, and away from fireplaces and furnaces.
Closed-house rules
MDH says any test shorter than 3 months needs closed-house conditions. Keep windows and outside doors shut except when you come and go. Run the heat and air conditioning the way you normally do. If the weather is severe or unusually windy, wait.
The heating season is the best time for a short-term test, according to MDH. A long-term test should cover some heating weather and some milder weather.
After you start
Read the expiration date. Fill out the card that comes with the kit. When the time is up, mail it the way the instructions say, if it is a mail-in kit. Save the result.
MDH says to retest every 2 to 5 years, and again after you finish a basement, add on, tighten the house, or change the heating and cooling system. Retest after a mitigation system is installed.
What the number means is on understanding radon results.