When Is Radon Testing Necessary?

On this page (7 sections)

1. When is radon testing necessary in a home?
2. Do I need a radon test when buying or renting a home?
3. Is radon testing necessary in new construction?
4. When should you retest for radon?
5. What is radon testing, and why do you need it?
6. What should you do after a radon test?
7. When is radon testing necessary? Use this decision rule

Radon testing is necessary when you've never tested your home, after major renovations, or when a prior result or mitigation system calls for a follow-up. Radon can enter through openings in foundations, and testing is the way to learn whether it has built up indoors.

If you're asking, “Do I need a radon test?”, the simplest answer is yes if you don't have a recent result for your home. Radon is odorless, so smell and appearance cannot tell you whether the level is high.

When is radon testing necessary in a home?

Test if you don't have a reliable, recent result for the home. Radon levels can differ between neighboring houses, so a nearby test cannot tell you your home's level.

A test is also useful after major changes to the home, such as finishing a basement, altering the foundation, or adding a room. If you are also planning a mold check, see mold and radon testing.

These changes can affect how air moves through the lower levels.

For a first screening, use the lowest level that people regularly occupy. Follow the test instructions about room choice, placement, and closed-house conditions.

If you're new to the process, start with What Is Radon Testing? A Beginner’s Guide.

It explains what a test measures and what the result means.

Do I need a radon test when buying or renting a home?

Ask for a radon result when buying or renting, and arrange a test if there isn't a recent one. For renter-specific steps, see testing radon as a tenant.

A result from a prior owner or tenant may not match current conditions if the house has changed.

For a home purchase, testing can be part of the inspection process. If a test is planned before closing, check that the method, location, and timing follow the test instructions and any local requirements.

Renters can ask the landlord or property manager whether the home has been tested. For unit-specific advice, see radon testing in apartments.

If the answer is unclear, a local health department may explain available testing options.

Is radon testing necessary in new construction?

Yes, testing is still useful in a newly built home. New construction can include features intended to reduce radon entry, but a test helps confirm the indoor level after the home is occupied.

Test when the home is operating under normal living conditions, and follow the test's guidance about closed windows and doors. For placement and timing details, see how to test for radon in new construction.

When should you retest for radon?

Retest after major renovations, after a mitigation system changes, or when your earlier result suggests follow-up. A new test can show whether conditions have shifted.

If a previous result was close to the action level used by your local health authority, consider a longer test or a second measurement before deciding what to do. For weather-related questions, see radon levels when it rains.

Check local guidance for the right next step.

For a mitigation system, follow the system professional's monitoring advice and keep records of test dates, locations, and results. Our guide to how often you should test for radon covers common retesting situations.

Should you choose a short-term or long-term radon test?

A short-term test is a practical first screen, while a long-term test gives a broader picture of exposure over time. Choose based on how quickly you need a result and the guidance for your situation.

Short-term tests are useful when you need an initial answer or have a time-sensitive decision. A longer test can capture more changes in radon levels across days and seasons; learn what a long-term radon test is.

What is radon testing, and why do you need it?

Radon testing measures the amount of radon in indoor air. You need it because radon has no reliable smell or visible sign, and a measurement is needed to know the level in a home.

A test may use a device left in a room for a set period, then analyzed according to its instructions.

Some kits use a mail-in sample; others display a reading. Learn how to test for radon: the simple answer before choosing a method.

Do you need a radon test kit?

A radon test kit can be a convenient first step if you can follow its instructions and send the sample as directed. Check the testing period, lab process, and any extra fees before choosing one.

A kit is not a substitute for a qualified radon professional when a result calls for mitigation or when you need a formal measurement for a transaction. See what a radon test kit is for an overview.

The First Alert Radon Gas Test Kit is intended for use in the United States. Its results are emailed within 72 hours of lab receipt, so allow for the test period and mailing time as well.

PRO-LAB describes this kit as a 48-hour test with email and text updates. Follow the instructions for collecting and returning the sample.

Leaping Lynx says results are typically reported 3–5 business days after the lab receives the sample. Use the lowest livable level and follow the kit's placement directions.

What should you do after a radon test?

Compare the result with guidance from your local or national health authority. If it is high or near an action threshold, confirm the result and ask a qualified radon professional about next steps.

Keep the result with the test date, location, and method. Those details help you compare future measurements and explain the home's history to a buyer, tenant, or service professional.

If the result is low, save it and consider retesting after substantial home changes or when local guidance recommends it. A single measurement describes the tested conditions and time period.

When is radon testing necessary? Use this decision rule

If your home has no recent test, test now. If you've renovated, changed a mitigation system, or received a result that needs follow-up, test again and use local guidance to choose the method.

For a first screen, choose a kit whose timing and lab steps fit your needs. Use how often to test for radon to plan a sensible follow-up schedule.

Frequently asked questions

Do I need a radon test if I live on an upper floor?

Testing can still be useful because radon levels vary between homes and can be present above basements. Test the lowest level you regularly use, following the kit's placement instructions; if you rent, ask the owner or local health department about testing options.

Do I need radon testing after buying a home?

If you don't have a recent, reliable result for the home, arrange a test after you move in. A previous owner's result may not reflect current conditions if the home has changed or the test location and method are unclear.

Is radon testing necessary in a new home?

Yes, a new home can still have radon, so testing is a useful check after construction. Test after the home is occupied and operating normally, and follow the test instructions for placement and closed-house conditions.

How often should I test for radon?

Retest after major renovations, after changes to a radon mitigation system, or if the earlier test was short-term and close to an action threshold. If your home has a mitigation system, follow its monitoring guidance and local recommendations.