Before you begin. This procedure is general reference information, not professional advice. Equipment varies by manufacturer, model, and year. Always follow the documentation supplied with your equipment — where it differs from this page, follow the manufacturer. Verify that you have the tools, the working conditions, and the ability to do this task safely. If anything is unclear, if the equipment is damaged, or if the task exceeds your experience, stop and use a qualified professional. You are responsible for your own safety and for the outcome. This site accepts no liability for any loss, damage, or injury arising from the use of this information.
Specifications marked unverified could not be traced to a manufacturer source. Do not rely on them — obtain the value from your equipment documentation.
Summary
Radon is a radioactive gas from rocks and soil that seeps into buildings. It has no colour, smell or taste. No amount of radon exposure is safe. Radon causes lung cancer, the second leading cause in the United States after smoking.
Most people do not know whether their home has radon. Testing is the only way to know. A short-term radon test runs for two days to 90 days, depending on the kit, in the lowest level of a home with windows and doors closed.
Follow the period printed in your kit's instructions. You send the device to a laboratory, which reports the radon level in pCi/L (picocuries per litre). The EPA action level is 4 pCi/L. This page covers testing and reading results only.
Safety
RADON IS A RADIOACTIVE GAS THAT CAUSES LUNG CANCER.
No safe level of radon exposure exists. Radon and smoking together multiply the risk.
Necessary equipment
| Item | Note |
|---|---|
| Radon test kit | Follow the instructions that come with the kit. |
| Tape (if required) optional | Some kits require sealing for transport. |
| Calendar or clock | Record the start time and the end time of the test. |
Prepare for the test
Estimated 6 min to 18 min
- Obtain a radon test kit from a qualified provider.3mReport a problem with step 1, Prepare for the test
- The EPA maintains a list of qualified test kit providers on its website.
- Contact your state radon program for a list of approved providers.
- Read the instruction sheet that comes with the kit.2mReport a problem with step 2, Prepare for the test
- Follow the specific placement and procedure instructions for your kit.
- Different kit types may have different requirements.
- Identify the lowest level where people live.1mReport a problem with step 3, Prepare for the test
- If people occupy the basement, put the test there.
- If not, put it on the ground floor.
- Radon levels are highest in the lowest part of a home.
Close the house
Estimated 4 min to 12 min
Source: Protocols for Radon and Radon Decay Product Measurements in Homes (EPA 402-R-92-003) · tier 1 · accessed 2026-08-03
DO NOT DISTURB THE TEST DEVICE DURING THE MEASUREMENT.
A disturbed device gives invalid results. Disturbance is illegal in some states.
- Close all windows and external doors in the home.3mReport a problem with step 1, Close the house
- Keep windows closed on all levels of the house.
- Close all doors to the outside, except for normal entry and exit.
- Stop whole-house fans and window fans from running.<1mReport a problem with step 2, Close the house
- Stop whole-house fans.
- Stop window fans.
- The furnace may run. It circulates only indoor air.
- Keep the house closed for twelve hours before you start testing.<1mReport a problem with step 3, Close the house
- Closed conditions allow radon levels to reach equilibrium.
- Do not start the test early.
- Results are inaccurate if you start too soon.
Place the test device
Estimated 4 min to 9 min
- Choose where to put the test device in the lowest level.2mReport a problem with step 1, Place the test device
- Put the device in a room where people spend time.
- Do not put the test in a furnace room or storage room.
- Do not put it in a bathroom or kitchen if you can help it.
- Read the kit instructions for placement rules.
- Place the device where the kit instructions say.1mReport a problem with step 2, Place the test device
- Most devices go on a shelf or table one to two metres high.
- Follow the kit placement guidance exactly.
- Record when the test starts.<1mReport a problem with step 3, Place the test device
- Write the start date and time in the kit notes.
Maintain the test
Estimated under a minute
- Keep windows and doors closed during the test.<1mReport a problem with step 1, Maintain the test
- Brief entry and exit is acceptable.
- Do not leave windows or doors open longer than a few minutes.
- Do not open windows for fresh air during testing.
- Do not disturb or interfere with the test device.<1mReport a problem with step 2, Maintain the test
- Keep the device undisturbed in its placement location.
- Do not move the device or cover it with anything.
- Keep fans stopped during the entire measurement.<1mReport a problem with step 3, Maintain the test
- Keep all window fans and whole-house fans stopped.
- The furnace may continue to run.
End the test and send the kit
Estimated 48 hr 6 min to 48 hr 34 min
Source: Protocols for Radon and Radon Decay Product Measurements in Homes (EPA 402-R-92-003) · tier 1 · accessed 2026-08-03
Source: Protocols for Radon and Radon Decay Product Measurements in Homes (EPA 402-R-92-003) · tier 1 · accessed 2026-08-03
- Allow the test to run for a minimum of two days.48hReport a problem with step 1, End the test and send the kit
- Short-term radon tests run from two days to 90 days.
- Obey the test period in the instructions for your kit.
- Keep the building closed for the full test period.
- Record the date and time the test ends.<1mReport a problem with step 2, End the test and send the kit
- Write down the end date and time in the kit documentation.
- Remove the device from the home.1mReport a problem with step 3, End the test and send the kit
- Handle it carefully per the kit instructions.
- Some kits require sealing for transport.
- Send the device to the laboratory per the kit instructions.5mReport a problem with step 4, End the test and send the kit
- Mail the device to the address in the kit.
- Use the correct labels and postage.
Read and interpret the result
Estimated 6 min to 35 min
Source: What is EPA's Action Level for Radon and What Does it Mean? · tier 1 · accessed 2026-08-03
Source: What is EPA's Action Level for Radon and What Does it Mean? · tier 1 · accessed 2026-08-03
- Receive the results from the laboratory.<1mReport a problem with step 1, Read and interpret the result
- The laboratory sends you the radon measurement in pCi/L (picocuries per litre).
- Compare the result to the EPA action level of four pCi/L.1mReport a problem with step 2, Read and interpret the result
- Four pCi/L or above: you must mitigate.
- Two to four pCi/L: consider mitigation.
- If the result is below two pCi/L, no action is required.<1mReport a problem with step 3, Read and interpret the result
- You may conduct testing again later.
- Run a test again if you occupy a basement.
- Run a test again if you renovate your home.
- If the result is four pCi/L or higher, contact a mitigation professional.5mReport a problem with step 4, Read and interpret the result
- Most states require a license for radon mitigation work.
- The professional assesses your home and recommends fixes.
Terminology
This page uses one term for each item and holds it throughout, as ASD-STE100 requires. Equipment sellers and other guides use the names below for the same parts.
- radon
- Also called: radon gas, radioactive gas in soil, cancer-causing gas, basement gas
- pCi/L
- Also called: picocuries per litre, picocuries per liter, radon measurement unit
- closed-house conditions
- Also called: closed-building conditions, windows and doors closed, depressurization conditions
- action level
- Also called: EPA action level, remedial action level, mitigation threshold
- radon decay products
- Also called: radon daughters, radon progeny, radon byproducts
- short-term test
- Also called: short-term radon test, radon test kit, short term radon test
- mitigation
- Also called: radon mitigation, radon remediation, radon system, radon reduction
When to use a professional
Stop at reading the result. Most jurisdictions require a licence for radon mitigation work. Your local radon program or a certified professional can assess your home and install systems. No safe radon level exists. Fix homes at or above 4 pCi/L. Consider mitigation between 2 and 4 pCi/L.
Common questions
What is radon and why should I test for it?
Radon is a radioactive gas that comes from rocks and soil beneath your home. It seeps in through cracks and gaps in the foundation and cannot be seen, smelled, or tasted. Radon is the second leading cause of lung cancer in the United States after cigarette smoking, and there is no safe level of radon exposure. The only way to know if your home has a radon problem is to test for it, because radon produces no immediate symptoms.
What is the EPA action level for radon?
The EPA recommends that homes be fixed if the radon level is 4 picocuries per litre (pCi/L) or higher. The EPA also recommends considering mitigation for homes between 2 and 4 pCi/L, since no safe radon level exists. For comparison, the average indoor radon level in American homes is about 1.3 pCi/L, and outdoor air averages 0.4 pCi/L.
How long does a radon test take?
It depends on the kit, and the range is wider than most people expect: EPA puts short-term tests at two days to 90 days, with 48 hours as the floor. A charcoal canister is often a 2 to 7 day device; other kits run much longer. Follow the period printed in your kit's own instructions rather than a number from a web page. If your test runs less than four days, EPA requires the house to be closed (windows and doors shut, high-volume fans off) for at least 12 hours before you start, and closed for the whole test. After the test ends you mail the device to a laboratory. This page previously said two to four days, which confused the closed-house threshold with the length of the test.
Where should I place the radon test?
Place the test device in the lowest lived-in level of your home, which is usually the basement if it is used as living space, or the ground floor if not. Radon levels are often highest in the lowest part of a building. The device should be placed in a room that is used regularly, such as a bedroom or living space, not in a furnace room, utility room, storage area or bathroom. Most devices are placed on a shelf or table at a height between one and two metres above the floor.
What are closed-house conditions?
Closed-house conditions mean that all windows and external doors are closed, except for normal entry and exit. High-volume fans and external air exchange systems (such as whole-house fans or high-volume window fans) should not be running. It is acceptable to run your heating and air conditioning furnace as normal because it re-circulates interior air. These conditions need to be in place for at least 12 hours before the test begins and must be maintained throughout the test period. Closed conditions allow radon and radon decay products to reach a stable concentration, which is necessary for accurate measurement.
What should I do if my result is above four pCi/L?
If your result is at or above 4 pCi/L (the EPA action level), the EPA recommends that your home should be fixed. Radon mitigation is licensed work in most jurisdictions, and you should consult a certified radon mitigation professional. They can assess your home and recommend mitigation solutions such as sub-slab depressurization, sealing cracks, or improving ventilation. This page covers testing only and does not provide instructions for mitigation.
Do I need to retest if my result is below 4 pCi/L?
If your result is below 4 pCi/L, retesting is not required by the EPA, but it is optional. Radon levels vary over time and by season, so you may want to test again in the future. Retesting is advisable if your living patterns change, such as if you begin using a basement as regular living space, or if you have made significant renovations to your home.
Related procedures
No related procedure is published yet. This section fills as the repository grows.
Sources
Every specification on this page is traced to one of these sources. Tier 1 is a manufacturer document, a published standard, or a government safety authority. See Standards for the full tiering rule.
- Tier 1What is EPA's Action Level for Radon and What Does it Mean?
- Tier 1How Often Should I Test/Retest My Home for Radon?
- Tier 1Radon and Radon Decay Product Measurement Protocols
- Tier 1A Citizen's Guide to Radon (EPA 402/K-12/002, 2025)
Revision history
Current version 2 · updated 2026-08-03 · next review due 2027-08-03
- v2 · 2026-08-03Corrected the short-term test duration. Version 1 published a maximum of four days and attributed it, with the two-day minimum and the 12-hour closed-house period, to a source id resolving to EPA's Radon Standards of Practice page - an inventory of ANSI/AARST standard editions that states none of the three. EPA 402-R-92-003, 'Protocols for Radon and Radon Decay Product Measurements in Homes', states 'Short-term tests are conducted for two days to 90 days.' The four days in version 1 was the threshold below which closed-building conditions become mandatory - 'short-term testing lasting less than four days' - read as if it were the length of the test. A reader following it would end a valid 7-day charcoal canister early and mail an incomplete measurement to the laboratory. Maximum corrected to 90 days; the two-day minimum and the 12-hour closed-house period are confirmed against the same document and now cite it. The 12-hour requirement carries its condition, which version 1 dropped: it is required for tests shorter than four days. Corrected in the summary, the task time, step 13, the FAQ and the terminology aliases. Version 1's claim that every safety-critical value came from a tier-1 EPA source was true of the action level and false of these three.
- v1 · 2026-08-03First draft. Scope is limited to placement of a short-term radon test kit and interpretation of results. Mitigation is licensed work and is refused and routed to a mitigation professional. Five tier-1 EPA sources: 'What is EPA's Action Level for Radon and What Does it Mean', 'How Often Should I Test/Retest My Home for Radon', 'Radon Standards of Practice' (endorsing ANSI/AARST standards), 'A Citizen's Guide to Radon', and 'Home Buyer's and Seller's Guide to Radon'. All procedures written independently in Simplified Technical English after sources were read and closed. Safety-critical values (action level 4 pCi/L, test duration 2-4 days, closed-house conditions 12 hours) are all from tier-1 EPA sources. Registering sources in data/sources.json is refused to a delegate and held in data/sources-additions-test-a-home-for-radon.json for merge. With that side file merged, the record should pass all thirteen checks.
Corrections to this page are listed in the public corrections log. Reports that are credible and not yet verified are listed in the public errata register, and an open one renders above the step it concerns.
Comments and corrections
Found an error? A correction with a manufacturer source is applied and logged publicly. You can also write to corrections@fixchecklist.com.
Every step above carries its own report control, which tags the report with that step so a correction reaches the right place. For anything about the procedure as a whole — the order of the sections, a step that is missing, something that did not match your equipment — use this: report something about this whole procedure.