Common Mistakes Homeowners Make When Doing DIY Radon Testing

Radon testing often feels simple on the surface, but small setup mistakes can quietly undermine the accuracy of your results. I’ve worked with many people who used DIY radon testing kits with good intentions but still ended up with misleading readings. In most cases, the issue wasn’t the test itself—it was how the test was set up or managed.

Because radon levels naturally fluctuate, accuracy depends on consistency, placement, and timing. Small changes in daily habits or environmental conditions can have a bigger impact than many homeowners realize. Understanding common mistakes ahead of time can make DIY radon testing far more reliable and less stressful.

Here are some of the most common mistakes homeowners make when doing DIY radon testing:

• Placing the radon testing device in the wrong location
• Failing to maintain closed-house conditions during radon testing
• Changing living habits during the radon testing period
• Ending the radon test too early
• Conducting radon testing during poor weather conditions
• Ignoring HVAC and ventilation system impacts on radon testing
• Mishandling or contaminating the radon test kit
• Misinterpreting DIY radon testing results

If you’re planning to test your home—or already have—knowing what to avoid can help you feel more confident in the results. Let’s take a closer look at each of these mistakes and why they matter.

Placing the Radon Testing Device in the Wrong Location

One of the most common mistakes I see involves where the radon testing device is placed. Location matters because radon levels are affected by airflow, pressure, and how a space is used. Testing in the wrong spot can produce results that don’t reflect everyday exposure.

Examples of locations that can interfere with accurate testing include:

• Near Windows or Exterior Doors: These areas experience frequent air exchange that can temporarily lower radon concentrations. As a result, readings may not reflect typical indoor conditions.
• Close to Vents or HVAC Returns: Air movement from vents can disrupt how radon accumulates in a room. This can lead to inconsistent or misleading measurements.
• Against Exterior Walls: Exterior walls are more influenced by temperature differences and pressure changes. These factors can affect the stability of radon readings.
• In Unused or Rarely Occupied Rooms: Radon testing is meant to measure exposure where people spend time. Testing in unused spaces may not reflect actual risk.

For reliable radon testing, the device should be placed in the lowest lived-in level of the home. That might be a basement, a finished lower level, or a frequently used room on the first floor.

Failing to Maintain Closed-House Conditions During Radon Testing

Closed-house conditions are essential for short-term radon testing because they help capture a realistic snapshot of indoor radon levels. When outside air is introduced too often, radon concentrations can be diluted. This can make results appear lower than they would be under normal conditions.

Situations that disrupt closed-house conditions include:

• Opening Windows for Fresh Air: Fresh air reduces indoor radon levels temporarily. This can result in readings that underestimate actual exposure.
• Leaving Exterior Doors Open for Extended Periods: Prolonged door openings affect indoor pressure balance. Even small habits can influence short-term test results.
• Running Whole-House Ventilation Systems Unnecessarily: These systems exchange indoor and outdoor air by design. During testing, this can interfere with measuring baseline radon levels.

Closed-house conditions don’t mean sealing the home completely. Normal entry and exit are fine, but windows and exterior doors should otherwise remain closed to maintain consistency.

Changing Living Habits During the Radon Testing Period

Another mistake homeowners make is altering their routines during radon testing. Turning off HVAC systems, avoiding certain rooms, or running fans differently can all affect indoor pressure. These changes can unintentionally skew the results.

Radon testing works best when it reflects real-life conditions. I always recommend living normally during the test period. The goal is to measure typical exposure, not a temporarily altered environment.

Ending the Radon Test Too Early

Radon testing requires patience, but it’s tempting to remove the test kit early. Some homeowners assume they’ve collected enough data before the minimum test duration is complete. Unfortunately, this can lead to unreliable readings.

Radon levels fluctuate throughout the day due to pressure and airflow changes. Following the manufacturer’s recommended exposure time allows the test to capture these variations. Completing the full test period is one of the easiest ways to improve accuracy.

Conducting Radon Testing During Poor Weather Conditions

Weather conditions can have a noticeable impact on radon testing results. Storms, strong winds, and rapid pressure changes may temporarily raise or lower radon levels indoors. Testing during extreme weather can create results that don’t reflect normal conditions.

While weather isn’t always predictable, timing your test during calmer conditions is helpful. If severe weather is expected, it may be better to wait. Stable conditions provide a clearer picture of typical radon levels in the home.

Ignoring HVAC and Ventilation System Impacts on Radon Testing

Heating, cooling, and ventilation systems play a major role in how air moves through a home. These systems can change indoor pressure, which affects how radon enters and circulates. Ignoring their influence can make test results harder to interpret.

Systems that can affect radon testing include:

• Bathroom and Kitchen Exhaust Fans: These fans pull air out of the home and can increase radon entry from below. Using them more than usual can skew results.
• Fireplaces or Wood Stoves: Active fireplaces alter airflow and pressure while in use. This can temporarily change radon patterns during testing.
• Whole-House Ventilation Systems: These systems intentionally circulate fresh air throughout the home. While beneficial overall, they can interfere with baseline radon measurements.

For the most accurate results, HVAC systems should be operated as they normally would during daily living. Consistency helps ensure the test reflects typical indoor conditions rather than a temporary setup.

Mishandling or Contaminating the Radon Test Kit

Radon test kits may seem simple, but they’re sensitive instruments. Touching the detector unnecessarily, moving it during the test, or placing it too close to objects can interfere with airflow. Even small disruptions can affect accuracy.

Once the kit is placed, it’s best to leave it undisturbed. Follow the handling instructions carefully when opening, sealing, and returning the test. Proper handling helps preserve the integrity of the results.

Misinterpreting DIY Radon Testing Results

Understanding radon test results can be confusing for homeowners. Some people worry unnecessarily over borderline readings, while others dismiss results that require follow-up. Knowing what the numbers mean is just as important as performing the test correctly.

A single radon test offers valuable information, but it doesn’t always tell the full story. In some cases, additional testing may be recommended. Interpreting results thoughtfully helps homeowners make informed, calm decisions.

Conclusion

DIY radon testing can be a useful and empowering step when it’s done carefully and thoughtfully. Most problems I see come down to small, fixable mistakes rather than major errors, and understanding those details can make a meaningful difference in accuracy. That understanding can help you feel more confident in your results and better equipped to make sense of your home’s indoor air. Taking the time to test carefully can turn what feels like a technical task into something much more manageable and reassuring.