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There is a silent and invisible intruder that could be seeping into your home, posing a serious risk to your family's health. It's radon, a naturally occurring radioactive gas that is the #1 cause of lung cancer among non-smokers in the United States. It's responsible for an estimated 21,000 deaths each year, more than drunk driving and home fires combined.

You cannot see, smell, or taste radon. The only way to know if your home has a problem is to test for it. The good news is that testing is inexpensive and easy, and if you do find high levels, the problem is entirely fixable. Taking this simple step is one of the most important things you can do to ensure the long-term health and safety of your indoor environment. This guide will walk you through everything you need to know.

What is Radon and Where Does It Come From?

Radon is a radioactive gas that forms from the natural decay of uranium, an element found in nearly all soils and rocks. As uranium breaks down, it releases radon gas, which then seeps up to the surface. Your home, typically at a lower air pressure than the surrounding soil, acts like a vacuum, actively drawing the gas in through:

• Cracks in concrete slabs and foundation walls
• Gaps around service pipes and utility lines
• Construction joints
• Sump pump pits

Once inside, the gas becomes trapped and can accumulate to dangerous levels. It doesn't matter if your home is old or new, drafty or well-sealed. Any home can have a radon problem.

Why is Radon Dangerous?

When radon gas is inhaled, it decays into radioactive particles that become trapped in your lungs. As these particles continue to break down, they release small bursts of energy that can damage the DNA in your lung tissue. Over time, this damage can lead to lung cancer. The risk is dose-dependent; the higher the radon level and the longer the exposure, the greater the risk.

The U.S. Environmental Protection Agency (EPA) estimates that 1 in every 15 homes in the U.S. has elevated radon levels. You can use our free air quality tool to see the average radon risk for your county, but remember: this is just an average. The only way to know your specific risk is to test your own home.

How to Test for Radon: Your Options

There are several reliable ways to test for radon, from simple DIY kits to professional-grade continuous monitors. Here's a comparison of the most common methods.

Step-by-Step Guide to Using a Short-Term Test Kit

A short-term test is the perfect starting point for most homeowners.

1. Purchase a Kit: You can buy a reliable kit like the First Alert Radon Test Kit online or at most hardware stores. The price typically includes the lab analysis fee.
2. Placement is Key: Place the test device in the lowest lived-in level of your home. If you use your basement as a family room, test there. If not, test your first floor. The device should be at least 20 inches off the floor, 1 foot from exterior walls, and away from drafts, high heat, or high humidity. Do not place it in a kitchen or bathroom.
3. Maintain Closed-House Conditions: For the entire test period (usually 48 to 96 hours), keep all windows and doors closed as much as possible. You can enter and exit, but don't air out the house. Run your HVAC system as you normally would.
4. Mail It In Promptly: After the testing period, seal the kit immediately and send it to the lab specified in the instructions. The charcoal in the kit begins to lose the trapped radon as soon as it's sealed, so mailing it quickly is important for accuracy.

For those who prefer ongoing data, a continuous monitor like the AirThings Wave Plus ($229) is an excellent investment. It not only tracks radon but also monitors CO2 and VOCs, giving you a complete picture of your indoor air quality right on your smartphone.

Interpreting Your Radon Test Results

Your radon level will be reported in picocuries per liter of air (pCi/L). Here's how to understand your number according to EPA guidelines:

• Below 2.0 pCi/L: This is a great result, representing low, background levels of radon. No action is needed.
• 2.0 to 3.9 pCi/L: This is a gray area. The EPA and World Health Organization suggest you consider fixing your home, as any radon exposure carries some risk. It's wise to conduct a long-term test to confirm the average before deciding on mitigation.
• 4.0 pCi/L and Above: This is the official EPA "action level." At this level, the EPA strongly recommends you take steps to reduce your home's radon levels.

It's important to know that the 4.0 pCi/L level is not a "safe" threshold. It is simply the point where the risk is considered high enough to warrant the cost of mitigation. The EPA's goal is to get indoor radon levels as close to outdoor levels (around 0.4 pCi/L) as is practicably possible.

What to Do if You Have High Radon Levels

If your results come back at 4.0 pCi/L or higher, don't panic. This is a common problem, and reliable solutions exist. The process of lowering radon is called radon mitigation.

The most common and effective method is active sub-slab depressurization. A certified mitigation professional drills a small hole in your foundation slab and installs a PVC pipe that runs from the soil beneath your home up to the roofline. A small, continuously-running fan attached to the pipe creates a vacuum, pulling the radon gas from the soil and venting it harmlessly above your house before it has a chance to enter.

A typical system costs between $1,200 and $2,500 and is highly effective, often reducing radon levels by up to 99%. A professional can typically install a system in a single day. A tell-tale sign of a mitigation system is the U-shaped pressure gauge (manometer) on the pipe, which shows you that the fan is running and the system is working.

Common Radon Myths, Debunked

• Myth 1: "New homes don't have radon." False. Modern, well-sealed homes can actually trap radon more effectively, leading to higher concentrations. The age of a home has no bearing on its potential for a radon problem.
• Myth 2: "My neighbor's house tested low, so mine is fine." False. Radon levels can vary dramatically from house to house due to differences in local geology and construction. Your neighbor's result tells you nothing about your own home.
• Myth 3: "A test in the summer is good enough." Not always. Radon levels are often highest in the winter due to the "stack effect," where warm air rising in the home pulls more gas from the soil. A long-term test that spans multiple seasons is the most accurate way to assess your risk.

Frequently Asked Questions

Do air purifiers remove radon?

No. Radon is a noble gas, and its individual atoms are far too small to be captured by even the best HEPA or carbon filters. While a purifier with a very thick carbon filter might adsorb a tiny, insignificant fraction, it is not an effective or reliable solution. The only proven way to address radon is with a proper mitigation system.

How often should I retest my home?

The EPA recommends retesting your home every two years to ensure levels remain low. You should also retest after any significant renovations, such as finishing a basement or putting on an addition, as this can change the air pressure and soil contact of your home.

Can I just open my windows to lower radon?

While opening windows will temporarily lower radon levels, it's not a practical or effective long-term strategy, especially during winter or in climates with high humidity. A mitigation system is the only reliable permanent solution.