Radon Testing: What Published Guidance Supports

Key takeaways

• EPA action level: 4 pCi/L or higher: fix the home
• Between 2 and 4 pCi/L: EPA recommends considering a fix
• Most useful single change: Test every home, whatever its age or location; neighbors' results do not predict yours.
• Commonest mistake: Assuming new homes or homes without basements are radon-free.
• See a doctor if any of the signs under "When to speak to a doctor" below apply to you.

What it is

Testing indoor air for radon, a radioactive gas from soil and rock that you cannot see, smell or taste. It sits within Environmental Health. Here are the numbers, taken from the guidance cited at the end.

The numbers, in one place

What helps

What follows is the practical part: the things guidance actually asks of you.

• Test every home, whatever its age or location; neighbors' results do not predict yours
• Use a short-term test kit, then a follow-up test if the result is 4 pCi/L or higher
• Hire a qualified radon mitigation contractor if levels are high; a common fix is a vent pipe and fan system
• Retest after mitigation and every 2 years afterward, and after major renovations
• Ask your state radon program about low-cost test kits

What to avoid

The common mistakes, including the ones that sound sensible.

• Assuming new homes or homes without basements are radon-free
• Testing with windows open or during a strong storm, which can skew results
• Smoking, which greatly increases the lung cancer risk from radon

In depth

Radon forms naturally when uranium in soil and rock breaks down. As a gas, it moves up through the ground and slips into buildings through cracks in foundations, gaps around pipes, sump pits and crawl spaces. Outdoors it disperses quickly, but indoors it can build up. The way a house is built, the soil beneath it and even the weather affect how much enters, which is why two neighboring homes can have very different readings.

The danger comes from what radon turns into. When you breathe it in, radon and its short-lived breakdown products can lodge in the lining of your lungs and release small bursts of radiation. Over years, that radiation can damage the DNA in lung cells, raising the chance that a cancer will develop. Radon causes no symptoms while you breathe it, and it does not cause headaches, rashes or other short-term illness, so a home can feel perfectly comfortable while still carrying a high level.

The risk depends on both the level and how many years you are exposed, which is why the focus is on long-term averages rather than a single day's reading. Smoking multiplies the effect: people who smoke and live with high radon have a much higher lung cancer risk than people exposed to either alone. The encouraging part is that radon problems are well understood, testing is inexpensive, and proven mitigation systems can bring levels down substantially in most homes.

Causes and risk factors

• Uranium-bearing soil and rock beneath the home, which varies widely by area
• Cracks in slabs and foundation walls, and gaps around pipes and wiring
• Basements, crawl spaces and sump pits open to the soil
• Lower air pressure inside the home, which draws soil gas in, especially in winter
• Radon released from private well water during showering and washing
• Tightly sealed homes with little ventilation, which can let levels build

How it is checked

There is no medical test that measures how much radon you have breathed. The home is what gets tested. Short-term tests, which stay in place for a few days up to about three months, give a quick snapshot and are a good first step. Long-term tests, left for more than 90 days, give a better picture of your year-round average because radon rises and falls with seasons and weather. A qualified radon measurement professional can also test, and is commonly used during home sales.

For your health, the question your doctor will focus on is your overall lung cancer risk. Radon history is worth mentioning, but current US screening guidance from the USPSTF is based on age and smoking history: yearly low-dose CT scans are recommended for adults 50 to 80 who have a 20 pack-year smoking history and smoke now or quit within the past 15 years. Your doctor can explain whether you qualify and what screening involves.

Treatment and support options

Confirming a high result

If a short-term test comes back at 4 pCi/L or higher, EPA advises a follow-up test before deciding on repairs. A second short-term test gives a quick confirmation, while a long-term test gives a better yearly average. If the average of two short-term tests, or a single long-term result, is at or above the action level, plan to fix the home. Place tests on the lowest lived-in level, away from drafts, outside walls and humidity.

Soil depressurization systems

The most common fix pulls radon from beneath the foundation before it can enter. A contractor drills into the slab or seals a crawl space, connects a pipe and runs a fan that vents the gas above the roofline. Sealing cracks helps but is rarely enough on its own. The fan runs constantly, and most systems include a gauge so you can see at a glance whether it is working.

Choosing a qualified contractor

Your state radon program can tell you how to find a certified or qualified mitigation contractor in your area. Get more than one estimate, ask how the contractor will confirm the result, and make sure the system and fan are labeled. A good contractor will also explain what to check in the years ahead, such as fan noise or the pressure gauge reading.

Treating radon in well water

If you use a private well in an area with radon in groundwater, the water can add to indoor air levels when it is released in showers and laundry. Water can be tested separately. Treatment systems such as aeration units or granular activated carbon filters can remove radon from water, and your state program can advise which suits your home.

Prevention

• Test when you move into a home and before buying or selling one
• Ask builders about radon-resistant construction features in new homes
• Retest after finishing a basement, adding an addition or changing the heating system
• Check your mitigation system gauge regularly and listen for changes in the fan
• Quit smoking and keep your home smoke-free to lower your combined risk

Day to day

Once a mitigation system is in place, life in the home carries on as normal. Check the gauge every so often; if the liquid levels on a U-tube manometer even out, the fan may have stopped. Fans typically last for years but do eventually need replacing, and the cost of running one is usually modest. Keep the test results and installation paperwork, since buyers will often ask for them, and plan a retest every couple of years.

If you lived for years in a home with high radon, it is natural to worry about the past. The most useful step is to talk to your doctor about your full lung cancer risk, including smoking and family history, and to make the changes that lower risk from here on. If you smoke, quitting brings the largest benefit. Free help is available by calling 1-800-QUIT-NOW, and your doctor can discuss medicines that make quitting easier.

For specific groups

People who smoke or used to smoke

Radon and tobacco smoke together create a much higher lung cancer risk than either alone. Testing and fixing your home matters even more for you, as does quitting. If you meet the age and smoking-history criteria, ask your doctor about yearly lung cancer screening.

Renters

You can test a rented home yourself with an inexpensive kit. Rules on whether landlords must test or fix radon vary by state, so check with your state radon program. Share results in writing with your landlord, and keep a copy for your records.

Families with children

Children are not thought to be harmed in the short term, but radon exposure that begins in childhood can add up over a lifetime. Testing bedrooms and playrooms on the lowest lived-in level makes sense, especially if children spend time in a finished basement.

Questions to ask your doctor

• Given my radon exposure and smoking history, what is my lung cancer risk?
• Do I qualify for yearly lung cancer screening with low-dose CT?
• What are the benefits and downsides of screening for someone like me?
• What support is available to help me or my partner quit smoking?
• Which symptoms should prompt me to come in sooner?
• Is there anything about my lung health I should watch more closely?

More questions, answered

Do apartments need radon testing?

Radon is usually highest on the lowest floors, so ground-floor and basement units are most worth testing. Higher floors usually have lower levels, but elevated readings can still happen. If you live on a lower floor, a simple test is a reasonable step, and your state radon program can advise.

Can an air purifier remove radon?

Standard air purifiers are not a substitute for mitigation. Radon is a gas, and HEPA filters are designed to catch particles. The proven approach is to stop the gas entering the home, usually with a soil depressurization system, and then retest to confirm the level has dropped.

Is a digital radon monitor as good as a test kit?

Continuous digital monitors can be useful for watching trends over time and spotting changes, such as a mitigation fan failing. For decisions about repairs or a home sale, use a test device or professional measurement that meets the standards your state recognizes, and follow the placement instructions carefully.

Does opening windows lower radon?

Opening windows can temporarily lower levels by diluting indoor air, but levels usually return when windows close. It is not a reliable long-term fix, and it can skew a test result. For testing, keep windows and outside doors closed as directed, apart from normal coming and going.

Is radon a problem only in certain states?

Some regions tend to have higher levels, and EPA publishes radon zone maps, but high readings have been found in every state. Maps describe average risk across an area, not the level in your home. Testing is the only way to know your own home's level.

Should a home sale fall through over radon?

Not usually. High radon is a fixable problem. Buyers and sellers often agree on mitigation before closing or a price adjustment. Make sure testing follows your state's rules for real estate transactions, and ask for a post-mitigation test result as proof the system works.

Related topics

• Air Quality: What the Evidence Actually Says (Respiratory Health)
• Carbon Monoxide During Power Outages: What the Evidence Actually Says (Heat, Cold and Weather Safety)
• Sun Protection: What the Evidence Actually Says (Skin Health)
• Reducing Cancer Risk: Sorting the Evidence From the Noise (Cancer Awareness)

Where to go next

• Radon Testing: Common Questions Answered
• Radon Testing: Just the Figures
• Radon Testing — the reference entry
• Environmental Health: The Complete Guide
• What the Guidance Really Says About Mold at Home
• What the Guidance Really Says About Drinking Water and Private Wells

When to speak to a doctor

See your doctor about lung cancer screening and any symptoms if you have lived with high radon, especially if you smoke or used to. See your doctor for a cough that will not go away, coughing up blood, chest pain or unexplained weight loss, and call 911 for severe trouble breathing or coughing up large amounts of blood.

Where this comes from

• EPA — A Citizen's Guide to Radon
• National Cancer Institute — Radon and Cancer

How this page was put together

Every figure, recommendation and warning above is taken from the guidance named in Where this comes from. Nothing on this page is inferred, summarized or generalized beyond what those bodies publish: where they give a number, it is their number, and where they are silent, so are we. Pages are rebuilt whenever the underlying record changes. Sign-off by a named clinician, where it has happened, is shown at the top of the page along with the date.

Medical disclaimer

This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to your doctor, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 911.