How to test your home for radon (short-term vs long-term)

Short answer: Test the lowest lived-in level of your home. A short-term kit (2 to 90 days; charcoal kits usually a few days) gives a fast answer; a long-term test (more than 90 days) better reflects your year-round average. EPA recommends fixing your home at 4 pCi/L or more, and considering a fix between 2 and 4 pCi/L.

Safety: If you have a radon system, keep it running during the test, and wait at least 24 hours after it starts before a post-installation test.

Step by step

Close up the house. For a test shorter than four days, keep windows and outside doors closed, except for normal entry and exit, for at least 12 hours before and during the test.
Place the kit. At least 20 inches above the floor in the lowest lived-in level, away from drafts, high heat, high humidity and exterior walls. Not in a kitchen or bathroom.
Record start and stop. Write down the dates and times and follow the lab's instructions exactly.
Mail it promptly. Reseal and send the kit to the lab right away; delays can affect the result.
Follow up. If a short-term result is 4 pCi/L or higher, EPA suggests a follow-up test (long-term for a better average, or a second short-term if you need results quickly).

Radon test kits

QuickScreen Charcoal Radon Test Kit – NRPP Certified Home Test — $44.99
Radtrak Radon Test – Accurate Long-Term Testing — $76.99

Common questions

When should I test after a radon system is installed?

EPA guidance is no sooner than 24 hours after the system starts running and within 30 days of installation. After that, retest at least every two years.

Short-term or long-term test?

Short-term is faster; long-term gives a better picture of the yearly average because radon levels change day to day and season to season.

Does a radon system alarm measure radon?

No. System alarms watch fan suction. Only a radon test or monitor measures radon.

Shop radon mitigation parts Read your radon manometer

Related categories: Radon Mitigation Supplies. General information only; follow the equipment maker's instructions and local codes. Updated 2026-11-14.