Radon Testing at Home: Protecting Against Lung Cancer

Radon is a radioactive gas produced when uranium in soil and rock breaks down. It has no color, no smell, and no taste, and it enters buildings through cracks in foundations, gaps around pipes, sump pits, and crawl spaces. Once inside, it can accumulate.

The EPA estimates radon causes about 21,000 lung cancer deaths each year in the United States, with an uncertainty range of 8,000 to 45,000. It is the second leading cause of lung cancer overall and the leading cause among people who have never smoked.

This is one of the few significant cancer risks you can measure in your own house for under $25 and, if necessary, eliminate.

• 4 pCi/L is the EPA action level. At or above it, fix the home.
• 2 to 4 pCi/L is the range where EPA advises considering action, noting that reducing levels below about 2 pCi/L is technically difficult.
• 1.3 pCi/L is the average indoor level in the United States.
• 0.4 pCi/L is the average outdoor level.

At a sustained 4 pCi/L, out of 1,000 people, the EPA estimates about 62 smokers and about 7 never-smokers would develop lung cancer from radon. That gap is not a reason for smokers to test and others not to. It is a reason for smokers to treat an elevated result as urgent, because radon and tobacco multiply each other rather than simply adding.

There is no level at which radon is known to be harmless. The 4 pCi/L figure is a practical action point, not a safety boundary.

Choose a test type. Short-term tests stay in place 2 to 90 days, often just 2 to 7, and results come back in about two weeks. Long-term tests run more than 90 days and better represent your year-round average, because radon levels swing with season, weather, and how the house is being ventilated. A common approach is a short-term test first, followed by a long-term test if the result is near or above the action level.

Get a kit. Many cost under $25. Hardware stores carry them, state radon programs often provide free or discounted kits, and national radon hotlines can direct you. January is National Radon Action Month, when free kit programs are most common.

Place it correctly. Lowest lived-in level of the home. In a room you actually use, such as a bedroom, living room, den, or playroom, and not a kitchen, bathroom, or laundry. At least 20 inches above the floor. Away from drafts, exterior walls, windows, and heat sources.

Maintain closed-house conditions. For short-term tests, keep windows and exterior doors closed as much as possible, and for tests of two to three days, keep them closed for at least 12 hours beforehand. Avoid testing during severe storms or high winds.

Mail it in to the lab on the date indicated. A kit that sits on a counter for a week before mailing gives an unreliable result.

At or above 4 pCi/L: confirm with a second test, either a short-term test for speed or a long-term test for accuracy, then arrange mitigation.

Between 2 and 4 pCi/L: consider mitigating, and consider it more seriously if anyone in the household smokes or has smoked, or if children spend a lot of time on the lowest level.

Below 2 pCi/L: no action needed. Retest every two years, and after any major renovation, foundation work, or change in your heating and ventilation system, since all of these can change airflow.

The standard fix is active sub-slab depressurization. A pipe is run from beneath the foundation slab and an inline fan pulls soil gas up and vents it above the roofline before it can enter the living space. Sealing cracks alone is not a reliable fix, though it is done alongside the system. Crawl spaces are typically handled with a sealed membrane and similar suction.

These systems work. The EPA notes sub-slab suction achieves reductions of 50 to 99 percent, and some systems reduce levels by up to 99 percent.

On cost, current EPA material says most homes can be fixed for about the same cost as other common home repairs and advises getting estimates from certified contractors rather than relying on a single figure. Older EPA guidance put a typical system at roughly $800 to $2,500, which is still a reasonable planning range, varying by foundation type, house size, and region. Fan replacement, which is needed periodically, costs about $200 to $350 including parts and labor. The system also runs continuously and will show up modestly on your utility bill.

Use a contractor certified by a national radon proficiency program; most state radon offices maintain lists.

Retest after installation, within 30 days of the system going in but no sooner than 24 hours after it starts running. Then retest every two years to confirm the system is still doing its job, and keep an eye on the manometer gauge, the small U-shaped tube on the pipe, which shows at a glance whether the fan is working.

Anyone who smokes or has smoked, because of the multiplied risk. Anyone with a basement or ground-floor bedroom, office, or play area. Anyone buying or selling a home, since testing is standard in many transactions. And anyone who has simply never tested, which the EPA regards as reason enough.

• EPA: A Citizen's Guide to Radon (PDF)
• EPA: Consumer's Guide to Radon Reduction, how to fix your home
• EPA: Basic Radon Facts (PDF)
• National Radon Program Services: testing devices
• National Cancer Institute — Radon and Cancer Fact Sheet
• CDC — Radon and Your Health