Short-Term vs. Long-Term Radon Testing: Which One Do You Need?

If you have decided to test your home for radon — which is the right call for any Michigan homeowner who has not done it yet — the next question is a practical one: what kind of test should you get? You will likely encounter two main options when you start looking into it: short-term tests and long-term tests. They are not interchangeable, and understanding the difference helps you make sure you are getting results you can actually act on.

The Basic Distinction

Short-term radon tests are designed to measure radon levels over a brief window of time — typically anywhere from two to seven days, though some extend up to 90 days depending on the device used. They are deployed in the home, left undisturbed for the testing period, and then sent to a laboratory for analysis. Results come back relatively quickly, which makes them a popular choice when a decision needs to be made on a timeline.

Long-term tests measure radon levels over a period of more than 90 days, and ideally through a full year. Rather than capturing a snapshot, they build a picture of average radon exposure across different seasons, weather patterns, and home use conditions. The result is a more comprehensive representation of what the people living in that home are actually breathing over time.

Both approaches have legitimate uses. The right choice depends on your situation, your timeline, and what you plan to do with the results.

When Short-Term Testing Makes Sense

Short-term testing is the appropriate choice in a few specific scenarios.

The most common is a real estate transaction. When a home is being bought or sold and radon testing is part of the due diligence process, there is rarely time for a long-term test. A short-term test conducted under closed-house conditions — with windows and doors kept closed except for normal entry and exit — gives a result that can inform negotiations or contingencies within the timeframe a transaction requires.

Short-term testing also makes sense as an initial screening tool. If you have never tested your home and want to get a baseline reading quickly, a short-term test tells you whether you are likely dealing with a significant problem. A result that comes back well below 4 pCi/L in a properly conducted short-term test is reassuring. A result that comes back at 8 or 10 pCi/L tells you clearly that action is needed without waiting months for confirmation.

Short-term tests are also used after mitigation system installation to verify that the system is working effectively. In that context, speed matters — you want to confirm the system is performing as expected without waiting through an entire season.

When Long-Term Testing Makes Sense

Long-term testing is the gold standard for understanding your home's true radon exposure profile. Radon levels are not static. They fluctuate based on barometric pressure, seasonal temperature changes, wind conditions, soil moisture, and how the home is being used. A short-term test captures conditions during one specific window — which may or may not be representative of what is happening in the home throughout the year.

In Michigan, this seasonal variation is particularly significant. Radon levels tend to be higher during the heating season when homes are sealed up than during the summer when windows are open and air is moving more freely. A short-term test conducted in July may produce a lower reading than a test conducted in January in the same home. Neither reading is wrong — they are just measuring different conditions.

A long-term test smooths out these fluctuations and gives you a result that reflects average annual exposure — which is ultimately what matters for long-term health risk. If you are not in a hurry and your goal is simply to understand the radon reality in your home with the highest possible accuracy, a long-term test is the more informative choice.

Long-term testing is also the recommended approach for confirming mitigation system performance after an initial post-install short-term test. A system may show a strong short-term result that holds up over time, or conditions may vary. A long-term follow-up test provides lasting confidence.

Closed-House Conditions: A Critical Detail for Short-Term Tests

One of the most important factors affecting short-term test accuracy is something called closed-house conditions. For a short-term test to produce a valid result, the home needs to be operated with all windows and exterior doors kept closed — except for brief, normal entry and exit — for at least 12 hours before the test begins and throughout the entire testing period.

This requirement trips up a surprising number of homeowners, particularly during warmer months when opening windows is a natural habit. A short-term test conducted in a home with windows regularly open will likely understate the actual radon levels, producing a falsely reassuring result. If you are conducting a short-term test, closed-house conditions are not optional — they are what makes the result meaningful.

Long-term tests, by contrast, are designed to be conducted under normal living conditions. No closed-house protocol is required because the extended timeframe accounts for natural variation in how the home is used and ventilated across seasons.

A Practical Recommendation

For most Michigan homeowners testing their home for the first time with no particular time pressure, starting with a short-term professional test under proper closed-house conditions is a reasonable approach. It gives you actionable information quickly. If that result is above 4 pCi/L, the next step is either a confirmatory short-term test or moving directly to mitigation. If it is below 4 pCi/L but above 2 pCi/L — a range where some health organizations recommend consideration of mitigation — a long-term test can help clarify whether the result reflects typical conditions in your home or a lower-than-usual reading.

The most important test is the one that actually gets done. Whichever type fits your timeline and situation, the information it gives you is far more valuable than continuing to wonder.

At All Michigan Mitigation, we conduct professional radon testing throughout West Michigan and can help you determine which testing approach makes the most sense for your home and circumstances. Testing is where everything starts.

Visit us at allmichiganmitigation.com to schedule your test or learn more about what the process involves.

All Michigan Mitigation is a West Michigan radon testing and mitigation company dedicated exclusively to helping homeowners understand and eliminate radon risk in their homes.