Home Radon Testing Guide: How and When to Test Your House

Home radon testing is one of the simplest ways to check for a health hazard that has no smell, no color, and no immediate symptoms. Radon is a naturally occurring radioactive gas that can seep into homes from the ground, and testing is the only reliable way to know whether it is present at unsafe levels in your specific house.

Home Radon Testing: Why Every House Needs Its Own Check

Because radon levels can vary dramatically between two houses on the same street, national or regional averages tell you very little about your own home. The only way to know your actual exposure is a direct test inside your own living space, repeated periodically since levels can shift over time.

What Is Radon and Why Testing Matters

Radon forms from the natural breakdown of uranium in soil, rock, and water, and it can enter buildings through foundation cracks, gaps around pipes, and sump pits. According to the U.S. Environmental Protection Agency’s Citizen’s Guide to Radon, radon levels vary significantly from home to home, even among neighboring houses, so testing your own home is the only way to know your actual exposure level.

Radon levels can differ by season, by floor of the home, and by how tightly a house is sealed, which is why professional guidance recommends specific testing protocols rather than a casual one-time check.

Types of Radon Tests

Short-Term Tests

Short-term test kits typically remain in place for two to ninety days, depending on the device, and are the fastest way to get an initial reading. The EPA’s guidance explains that short-term tests should be conducted with windows and exterior doors closed as much as possible during testing, since airflow changes can skew results.

Long-Term Tests

Long-term tests run for more than ninety days and give a more accurate picture of a home’s year-round average radon level, since radon concentrations can fluctuate with weather and seasons. If your short-term result is elevated, a long-term test or a second short-term test is the recommended next step for confirmation.

Step-by-Step: How to Test Your Home

1. Choose a testing location. Place the kit in the lowest lived-in level of the home, such as a frequently used basement, or the first floor if the basement is not regularly occupied.
2. Position the kit correctly. The EPA recommends placing the kit at least 20 inches above the floor, away from drafts, exterior walls, high heat, and high humidity, in a room used regularly but not a kitchen or bathroom.
3. Close up the house. For short-term tests, keep windows and exterior doors closed as much as possible, ideally starting at least 12 hours before the test begins.
4. Avoid disruptive conditions. Do not run short-term tests during unusually severe storms or high winds, which can distort readings.
5. Leave the kit undisturbed. Let it sit for the full duration listed on the package instructions.
6. Send it for analysis promptly. Reseal the kit immediately after the test period ends and mail it to the lab specified on the packaging without delay.

Understanding Your Results

The EPA recommends a two-step testing process. First, take a short-term test. If the result comes back at 4 picocuries per liter (pCi/L) or higher, follow up with either a long-term test or a second short-term test to confirm the finding before deciding on next steps. This layered approach reduces the chance of overreacting to a single anomalous reading or underreacting to a genuine hazard.

What to Do If Radon Levels Are High

If confirmed testing shows elevated radon, mitigation systems, typically a vent pipe and fan system that redirects soil gas away from the home before it enters living spaces, can meaningfully reduce indoor radon levels. Mitigation should be installed by a qualified professional, and many state radon programs maintain lists of certified contractors. After any mitigation work, retest the home to confirm the system is working as intended.

The U.S. Centers for Disease Control and Prevention states that testing your home is the only way to know if radon levels are high, and that reducing radon levels in a home can help lower long-term risk. You can review the agency’s overview of how radon enters homes and how it is measured through the CDC’s radon resource page, which complements the EPA’s testing and mitigation guidance.

Mitigation costs and specific system designs vary depending on a home’s foundation type, whether it has a basement, crawl space, or slab foundation, and the severity of the radon reading. A qualified contractor will typically evaluate these foundation-specific factors before recommending a system design, since a one-size-fits-all approach is rarely appropriate.

Radon in New Construction and Existing Homes

Some newer homes are built with passive radon-resistant features, such as a vent pipe and sealed foundation, installed during construction in areas known for higher radon potential. Even homes built with these passive features should still be tested after move-in, since passive systems reduce but do not guarantee elimination of radon entry, and a fan can often be added later if a passive system alone is not sufficient.

Older homes without any radon-resistant construction features are not automatically at higher risk purely because of their age; radon potential is driven primarily by local soil and geology, not by the home’s construction date. This is one more reason why testing your specific home matters more than assumptions based on the neighborhood or the age of the structure.

When to Retest

Radon levels can change over time due to renovations, foundation settling, or changes in ventilation, so periodic retesting is a reasonable practice even in homes that previously tested low. Retesting is also recommended after any structural changes to the foundation, after installing a mitigation system, and when purchasing a home that has not been recently tested.

Quick Reference Checklist

• Test the lowest lived-in level of the home
• Position the kit at least 20 inches above the floor, away from drafts and humidity
• Close windows and exterior doors before and during short-term testing
• Confirm any result of 4 pCi/L or higher with a follow-up test
• Use a qualified professional for mitigation if levels remain elevated
• Retest periodically and after any renovation or mitigation work

Final Takeaway

Radon cannot be seen, smelled, or felt, which is exactly why structured testing matters more than instinct. Following a recognized testing protocol, understanding the two-step confirmation process, and knowing when to bring in a mitigation professional gives you a clear, evidence-based way to manage this specific indoor air risk in your own home.