One Test Is Never Enough: The Radon Retesting Schedule Every Nevada Homeowner Should Follow

Many Nevada homeowners breathe a quiet sigh of relief after receiving acceptable results from a single radon test. It is an understandable reaction — testing feels proactive, and a low reading seems like good news worth holding onto. The problem is that radon levels do not remain static. They shift with the seasons, respond to structural changes in your home, and fluctuate in response to the geological activity happening beneath your foundation. A test conducted two years ago may say very little about what you are breathing today.

This is not a fringe concern. It is a well-documented reality that the U.S. Environmental Protection Agency and radon health researchers have addressed directly in their testing guidance. Yet the message has not fully reached the majority of homeowners, who tend to treat radon testing as a one-time task rather than an ongoing practice.

Why Radon Levels Change Over Time

Radon originates in uranium-bearing rock and soil, both of which are abundant across large portions of Nevada. As uranium decays, it produces radium, which in turn releases radon gas. That gas migrates upward through the soil and enters homes through foundation cracks, construction joints, utility penetrations, and even porous concrete.

The rate at which radon enters a home is not constant. Several factors cause it to vary:

Seasonal pressure differentials. During colder months, the air inside a home is warmer than the air outside, creating a stack effect that draws soil gases — including radon — upward through the foundation. Nevada winters, while milder than those in northern states, still produce enough temperature contrast to meaningfully alter radon infiltration rates. Conversely, summer conditions in Nevada often involve tightly sealed homes running air conditioning, which can also trap radon that enters during ventilation cycles.

Soil moisture and atmospheric pressure. Rain, snowmelt, and shifts in barometric pressure influence how freely radon travels through soil. Saturated soil can temporarily block radon pathways, while dry or frozen ground may channel the gas more directly toward a home's foundation. Nevada's arid climate and periodic heavy rainfall events create variable soil conditions throughout the year.

Home modifications. Renovations that affect a home's envelope — adding a room, sealing a basement, replacing windows, or upgrading insulation — can alter the pressure dynamics that govern radon entry. Even something as routine as installing a new exhaust fan can change air circulation patterns enough to affect radon accumulation.

Natural geological shifts. Soil settles, foundation cracks expand, and subsurface geology evolves gradually over time. A home that tested safely five years ago may have developed new entry points that did not exist when the original measurement was taken.

What the EPA Actually Recommends

The EPA's guidance on radon testing is often summarized incompletely. Most homeowners are aware that the agency recommends testing if you have never done so. Fewer are aware of the full scope of that guidance.

The EPA recommends retesting every two years under normal circumstances, even if previous results were below the 4 picocuries per liter (pCi/L) action level. For homes that have undergone mitigation, retesting within 24 hours to 30 days after system installation is advised to confirm the system is functioning effectively. Retesting should then occur again within two years, and periodically thereafter.

The agency also recommends retesting after any significant renovation, after purchasing or selling a home, and after any major changes to the home's heating or ventilation systems. These are not optional precautions — they reflect the scientific understanding that radon exposure is a dynamic risk, not a fixed condition.

The Most Common Retesting Mistakes Nevada Homeowners Make

Understanding the retesting schedule is one thing. Avoiding the pitfalls that undermine accurate results is another. Several errors appear frequently among homeowners who test in good faith but end up with misleading data.

Relying on a short-term test as a final answer. Short-term tests, which typically run for two to seven days, are useful screening tools but are not designed to represent long-term average exposure. They are most valuable when used as a preliminary step, with a follow-up long-term test (90 days or more) to establish a reliable baseline. Using a short-term test result as permanent confirmation of safety is a significant misunderstanding of what the test is designed to measure.

Testing only in the basement and ignoring upper floors. Radon concentrations are typically highest in the lowest level of a home, but they do not stay there. In homes where occupants spend significant time on main living floors, testing only the basement may not reflect the actual exposure of household members. Multi-story homes warrant testing on multiple levels.

Testing during open-window conditions. Accurate radon testing requires closed-house conditions — meaning windows and exterior doors should remain closed (except for normal entry and exit) for at least 12 hours before and throughout the test period. Testing during warm months when windows are frequently open will produce artificially low readings that do not represent typical indoor exposure.

Assuming mitigation systems are permanent solutions that require no follow-up. Sub-slab depressurization systems — the most common mitigation approach — are mechanical systems subject to wear. Fans can lose efficiency, pipes can develop blockages, and system performance can degrade over time without producing any obvious signs. Post-mitigation retesting is the only reliable way to confirm that a system continues to perform as intended.

Skipping retesting after major home changes. A bathroom addition, a finished basement, or new weatherstripping around doors may seem unrelated to radon, but each can alter the pressure balance of a home in ways that affect radon entry. Any meaningful change to a home's structure or ventilation should prompt a fresh test.

Building a Testing Schedule That Actually Protects Your Household

A practical retesting schedule for Nevada homeowners might look like this:

• Initial testing: Conduct a long-term test (90 days or more) to establish a reliable baseline, ideally during the heating season when radon levels tend to peak.
• After mitigation: Retest within 30 days of system installation, then again at the two-year mark.
• Routine maintenance testing: Retest every two years in the absence of major home changes.
• After renovations or structural modifications: Test within 30 days of project completion.
• After purchasing a home: Conduct an independent test regardless of any prior results disclosed during the transaction.

Keeping a record of all test results, including dates, test types, and radon levels detected, creates a useful history that can help identify trends over time and inform decisions about mitigation or system maintenance.

The Cost of Complacency

Radon is the second leading cause of lung cancer in the United States, responsible for an estimated 21,000 deaths annually according to the EPA. Nevada homeowners face elevated risk due to the state's geology, and that risk does not diminish simply because a test conducted years ago returned acceptable numbers.

The reassurance that comes from a single test is real but limited. The reassurance that comes from a consistent, well-timed testing schedule is something far more durable — and far more protective of the people living inside your home.