Radon Testing in Denver: Short-Term vs. Long-Term Tests Explained

Testing is the only way to know whether radon is a problem in your home, but not all tests are the same. The right choice depends on your timeline, why you are testing, and how precise you need the result to be. Here is a clear breakdown of short-term versus long-term radon testing for Denver homeowners.

Short-Term Tests: Fast Answers

Short-term tests measure radon over a period of 2 to 7 days. They are the go-to choice when you need a quick result, such as during a real estate transaction. Charcoal canisters and continuous radon monitors both fall into this category. The trade-off is that radon levels fluctuate day to day, so a short snapshot is less representative of your year-round average.

• Duration: 2 – 7 days
• Best for: real estate deals, a quick initial screening, or confirming a mitigation system works
• Devices: charcoal canisters, continuous radon monitors
• Trade-off: a short window can be skewed by weather and how closed up the home is

Long-Term Tests: The Most Accurate Picture

Long-term tests run for more than 90 days, often a full season or longer. Because radon levels swing with temperature, barometric pressure, and how much you open windows, a long-term test gives the most reliable estimate of your true year-round exposure. If you are not under a deadline, this is the gold standard.

• Duration: 90+ days, ideally across seasons
• Best for: knowing your real long-term exposure
• Devices: alpha track detectors, electret ion chambers
• Trade-off: results take months, so not suited to a home sale timeline

Radon levels can be twice as high in winter as in summer. That is why a single short test is only part of the story.

Which Test Should You Use?

If you are buying or selling a home, a short-term test gets you a result inside the inspection window. If you simply want to understand the safety of the home you live in, start with a short-term test, and if it comes back borderline (between 2 and 4 pCi/L), follow up with a long-term test for a fuller picture. Any result at or above 4.0 pCi/L means it is time to mitigate.

• Below 2.0 pCi/L: low, but the EPA notes no level is truly risk-free.
• Between 2.0 and 4.0 pCi/L: consider mitigation and re-test long term.
• At or above 4.0 pCi/L: the EPA action level, mitigation is strongly recommended.

Testing Tips for Accurate Results

For any test, place the device in the lowest livable level of your home, keep doors and windows closed as much as possible during a short-term test, and keep the detector away from drafts, exterior walls, and high humidity. Following these closed-house conditions keeps your reading honest.

Not sure where to start? Custom Radon provides a complimentary test kit with every free in-person estimate and can interpret your results for you. If mitigation is needed, we guarantee levels below 4.0 pCi/L and stand behind it with a lifetime warranty.