The homeowner’s reference
Radon test kits and monitors: how the three types compare
Short-term kits measure for 2–90 days and are mailed to a lab. Long-term kits measure for more than 90 days and better reflect a home's year-round average. Continuous monitors show readings as they go. EPA's first step is a short-term test, followed by a second test if the result is 4 pCi/L or higher.
Sources: EPA: A Citizen's Guide to Radon (PDF).
1. Short-term kits: the quickest first test
A short-term test stays in the home for 2–90 days, depending on the device. EPA lists charcoal canisters, alpha track, electret ion chamber, continuous monitor and charcoal liquid scintillation detectors as common short-term devices.
Radon varies from day to day and season to season, so a short-term result is less likely than a long-term one to show the year-round average. For a test lasting only 2–3 days, EPA says to close windows and outside doors at least 12 hours beforehand and keep them closed during the test.
Sources: EPA: A Citizen's Guide to Radon (PDF).
2. Long-term kits: a better read on the yearly average
A long-term test stays in place for more than 90 days. EPA names alpha track and electret detectors as the usual devices. The result is more likely than a short-term test to reflect the home's year-round average level.
EPA suggests a long-term follow-up when you want that better understanding and do not need a result quickly.
Sources: EPA: A Citizen's Guide to Radon (PDF).
3. Continuous monitors: readings as they happen
A continuous monitor records radon over time instead of being sent to a lab at the end. EPA includes continuous monitors among short-term testing devices. Consumer digital monitors differ in design and documentation, so read the manufacturer's instructions for placement and how long to wait before relying on a reading.
If a monitor shows an elevated level, confirm it with a lab-analyzed test or a credentialed tester before deciding on mitigation.
Sources: EPA: A Citizen's Guide to Radon (PDF).
4. Place any kit where it gives a usable result
EPA's guidance is to test in the lowest lived-in level of the home, in a regularly used room but not a kitchen or bathroom. Place the kit at least 20 inches above the floor, away from drafts, high heat, high humidity and exterior walls.
Leave the kit for as long as the package says, then reseal it and send it to the lab right away. EPA says results usually arrive within a few weeks.
Sources: EPA: A Citizen's Guide to Radon (PDF).
5. Where to get a kit
Test kits are sold online and in home-improvement stores. EPA also points to discounted kits from the National Radon Program Services at Kansas State University, and notes that some state radon programs offer free or discounted kits.
If you are buying or selling a home, EPA notes you can hire a qualified tester instead. Some states license radon testers; check the rules for your state before relying on a do-it-yourself result in a transaction.
Sources: EPA: Find a Radon Test Kit or Measurement and Mitigation Professional; EPA: A Citizen's Guide to Radon (PDF).
Before you buy a kit
- Short-term or long-term: do you need a quick answer or the yearly average?
- Does the price include lab analysis and return shipping?
- Does your state radon program offer a free or discounted kit?
- Which room is the lowest regularly used level?
- Who will you call if the result is 4 pCi/L or higher?
Find a credentialed provider
If a result is elevated or you need a test for a home sale, find a credentialed tester or mitigator for your city or county and check the credential against the official source.
Find providers in your area · Check credentials by state
Testing instructions and requirements depend on the test, building and jurisdiction. Use the linked agency guidance and your qualified professional’s instructions for your situation.