How to Test a Basement for Radon

On this page (8 sections)

1. Where should you place a radon test in a basement?
2. How do foundation walls, sumps, and drafts affect placement?
3. How do you prepare the basement before testing?
4. How long should a basement radon test run?
5. What should you do while the test is running?
6. How do you send a basement radon test to the lab?
7. What does a basement radon result mean?
8. What is the simplest way to test a basement for radon?

To test a basement for radon, put a short-term test in a regularly used room on the lowest lived-in level, away from drafts, exterior walls, windows, doors, and openings such as sumps. If you also use a private well, see how to test water for radon.

Follow the kit instructions for the test period and any steps for sending the sample to a lab.

If you’re asking, “How do I test for radon in my basement?”, start by choosing a spot that reflects the room’s normal air, not a drafty corner or the area right beside a foundation opening. Our How to Test for Radon: The Simple Answer covers the general process.

Where should you place a radon test in a basement?

Place the test in a room people use regularly on the lowest lived-in level, following the instructions for your specific kit. A finished family room or home office may be a better choice than a storage room no one enters.

Keep the test away from exterior walls, windows, doors, vents, and direct drafts. Don’t put it beside a sump pit, floor drain, or foundation crack.

Radon can enter through openings like these, but testing right beside one may not represent the air you normally breathe.

Set the test on a stable surface where it won’t be covered, moved, or disturbed. If you are also checking for mold, see mold and radon testing.

Avoid kitchens, bathrooms, and laundry rooms if the kit instructions say to keep it away from areas with high humidity or frequent air movement.

How do foundation walls, sumps, and drafts affect placement?

Keep the test away from foundation walls and openings, including sump pits and drains. Cracks, construction joints, and spaces around pipes can be entry routes for radon, so a test directly beside one could give a result that doesn’t reflect the rest of the room.

Don’t seal a sump or cover a foundation crack just to take a test. Choose an appropriate location and leave the home in its usual condition during testing, unless the kit or local guidance instructs otherwise.

Air movement can also affect a test. Avoid spots near fans, vents, doors, windows, or other sources of drafts.

If your basement has a crawl space, see whether you need a crawl space dehumidifier; moisture control and radon testing are separate tasks.

How do you prepare the basement before testing?

Choose the location first, then read the kit instructions before opening or setting up the test. Each test has its own exposure period, handling steps, and return process.

Keep the test area as you normally use it. Don’t move the kit to a different room midway through, and don’t place it where children, pets, or stored items may disturb it.

Record the start time if the instructions call for it.

Some kits require a closed-house period or other conditions. Follow those directions exactly, including any requirements for doors and windows.

For a broader home-testing walkthrough, see How to Test for Radon at Home: A Quick Guide.

How long should a basement radon test run?

Use the exposure period printed in your kit instructions. Short-term kits can have different test windows, so don’t assume every test runs for the same number of hours.

The First Alert Radon Gas Test Kit is intended for an initial screening and includes test materials and lab fees, excluding New Jersey state fees. First Alert says results are emailed within 72 hours of lab receipt.

The PRO-LAB Radon Test Kit for Home uses a short-term collection method with a 48-hour exposure period, followed by lab analysis. Its package includes the lab fee, and results are provided by email or text notifications.

The Leaping Lynx Radon Test Kit for Home also uses a 48-hour test period, with lab analysis included. Postage is required to return the detector, and results are typically reported 3–5 business days after the lab receives the sample.

Don’t compare results from tests taken under different conditions as if they were identical. Weather is one condition that can matter; see how weather affects radon levels.

If you need to know when to test again, read how often you should test for radon.

What should you do while the test is running?

Leave the test in place and avoid disturbing it for the full test period. Don’t move it to a more convenient room, cover it, or put it near a fan to speed up air movement.

Keep doors and windows in the condition required by the kit. If people need to use the basement, they can continue normal activity unless the instructions say otherwise.

Avoid major changes to heating, cooling, or ventilation during the test.

If the test is damaged, moved, or exposed to conditions outside the instructions, contact the kit provider or testing lab for guidance. Don’t assume the result is valid if the test was interrupted.

How do you send a basement radon test to the lab?

Follow the kit’s return instructions as soon as the exposure period ends. Some tests require sealing the device and mailing it in promptly, while others have different steps.

Check radon test kit expiration dates and deadlines before testing.

Complete any registration or submission form, package the sample as directed, and use the return method supplied with the kit. Note the date you finished the test so you can compare it with the result report.

A test kit is one way to screen a home. Learn what a radon test kit is if you want to understand the difference between the collection device and the lab analysis.

What does a basement radon result mean?

Use the result as a screening measurement and follow current public health guidance if it is raised. Radon levels can vary, so a single measurement may not describe every room or every season.

Read the lab report carefully and check its units and recommendations. If the result is above the action level used by your local authority, ask a qualified radon professional about confirmation and mitigation options.

A basement test does not automatically tell you the level in every room upstairs. For other situations that call for testing, see when radon testing is necessary.

If your home is newly built, review radon testing in new construction for questions specific to that situation.

What is the simplest way to test a basement for radon?

Choose a regularly used room on the lowest lived-in level, place the test according to its instructions, and keep it away from drafts, exterior walls, sumps, and drains. For a multi-unit home, see radon testing in apartments.

Leave it undisturbed for the required period and return it as directed.

Pick a kit based on its test duration and return process. First Alert includes lab fees except for New Jersey state fees, PRO-LAB uses a 48-hour test with lab analysis included, and Leaping Lynx uses a 48-hour test with postage required for return.

Frequently asked questions

Where should I place a radon test in a basement?

Place the test in a room people use regularly on the lowest lived-in level, following the kit's instructions. Keep it away from drafts, exterior walls, windows, doors, sumps, drains, and other openings.

Avoid kitchens, bathrooms, laundry rooms, and spots where the test could be bumped or covered.

Can I test for radon near a sump pump?

Don't place a test beside a sump pit or pump. Openings around sumps can be radon entry points, but a test placed close to one may not represent the air in the room.

Choose a stable spot in a regularly occupied basement room and follow the kit's placement rules.

Should I test a basement if nobody sleeps there?

Yes, a basement can be the lowest lived-in level even when nobody sleeps there. Test a room used regularly, such as a finished family room or home office, rather than an isolated storage area.

If the basement isn't lived in, follow current public health guidance for the lowest level that could be used.

What should I do if my basement radon test is high?

Follow the test instructions and your local public health guidance for confirming a raised result. A qualified radon professional can assess the home and discuss ways to reduce radon.

Don't rely on ventilation or a single spot check as a fix, and retest after any mitigation work.