What to expect during a radon test

A short-term radon test usually sits in the lowest lived-in level of your home for 2 to 7 days. You keep the windows and outside doors closed while it runs. The result comes back in pCi/L.

What do you need to do during the test?

Your tester's instructions or the kit instructions come first. For a test shorter than 96 hours, Illinois says to close up the home at least 12 hours before the test starts and keep it that way until the test ends:

• Keep all windows and outside doors closed. Coming and going is fine, but do not air the home out
• Run your furnace and central air as usual. Air conditioning that recirculates indoor air can run
• Do not use a whole-house fan. Follow the written instructions for the dryer, range hood, and bathroom fans, since they can change the result
• Do not run ceiling fans, portable air filters, humidifiers, or dehumidifiers within 20 feet of the test
• Do not move the test

Under the Illinois rules for professionals, tests shorter than 96 hours are not run during severe storms or long stretches of high wind. Remodeling, or heating and cooling work that changes how air moves through the home, can also throw off a test. A licensed tester may reschedule instead of giving you a result they can't trust.

Short-term or long-term?

There are two kinds of home radon tests: short-term and long-term. Under Illinois rules, a short-term test runs anywhere from 2 to 90 days. A long-term test lasts at least 91 days, so its number is closer to your home's average for the year.

Illinois starts both homeowner tests and home-sale tests with a short-term test. Our short-term or long-term guide has the 48-hour rules for a sale.

What kinds of test devices are there?

Illinois approves several kinds. Passive devices include activated charcoal kits, charcoal liquid scintillation kits, and short-term electret detectors. Continuous radon detectors use power and record a reading at least once an hour. Some passive devices get sent to a licensed lab. A continuous detector keeps its own hour-by-hour readings and average.

Where the test goes depends on how the home is built, not which room is easiest to reach. Illinois calls for a test in every lowest part of the home where someone could live. So a home with a basement, a room over a crawlspace, and a slab section may need a test in each one.

When your result comes back

4.0 pCi/L is the EPA action level. What your radon test result means covers that number and the Illinois rules for what comes next.