Short-Term vs Long-Term Radon Tests: Which to Choose
Radon in the same house can read 90 in July and 250 in January. Same basement. Same family. The gas just moves more in winter. That one fact is why picking the right test matters more than most people think.
A short-term test gives you a fast snapshot. A long-term test gives you a real yearly average. Neither one is “better.” They answer different questions.
Here’s how to pick the right one for your home, your budget, and your timeline.
The short version:
- A short-term test runs 2 to 7 days. It’s a fast screen, not a final answer.
- A long-term test runs 91 days or more. Health Canada trusts it most.
- Radon swings with the seasons, so a short winter test is more useful than a short summer one.
- Buying or selling a home? A short-term test fits the deadline.
- Deciding whether to spend on a mitigation system? Use a long-term test.
- BRF short-term test is $99. Long-term is $299. Both follow Health Canada protocol.
What’s the difference between short-term and long-term?
The gap comes down to one thing: how long the device sits in your home.
A short-term test measures for 2 to 7 days. A long-term test measures for 91 days or more. That’s the core split.
A short-term test is a spot check. It catches your radon level during one short window. That window might be a calm week or a spike week. You don’t get to know which.
A long-term test averages your level across months. It rides through cold snaps, warm spells, and everything in between. The number you get is closer to what you actually breathe all year.
Think of it like weather versus climate. One day of rain doesn’t tell you the season. One week of radon doesn’t tell you the year.
Why radon levels swing so much
Radon comes up from the soil under your home. How much gets in changes day to day. That’s the whole reason two tests can disagree.
In winter, warm indoor air rises and escapes through the roof. That pulls soil gas up through cracks in the basement floor. This is the stack effect.
Closed windows and a running furnace trap that gas inside. So levels climb in the cold months.
Summer is the opposite. Open windows and less stack effect mean lower readings. A short test in July can read low while your true winter level is well over the guideline.
Weather matters too. A storm, a windy day, or a big temperature drop can move your number within hours. This is why a single short test is a screen, not a verdict.
Short-term radon test: the fast screen
A short-term test is the quick option. You get a number in under a week of run time.
Health Canada sets the floor at 48 hours.
There are rules that make the number trustworthy:
- Place the device in the lowest level you actually live in.
- Keep it away from drafts, windows, and outside walls.
- Shut windows and outside doors 12 hours before you start.
- Keep the house closed the whole time (normal in-and-out is fine).
A short-term test shines when you need speed. It’s a first screen for a curious homeowner. It’s the right tool for a home sale on a deadline. It’s how you find out fast if your home is probably fine or probably high.
The tradeoff is noise. One short window can miss a real problem or flag a false one. If a short test reads high, you confirm it before you spend money on a fix.
Long-term radon test: the real answer
Here’s the twist. The longest test gives you the most trustworthy single number.
A long-term test runs for at least 91 days.
Why so long? Because it averages out the swings. It counts the winter spikes and the summer dips. The result reflects how you really live, across seasons.
Health Canada calls the long-term test the best basis for deciding whether to fix your home.
The only downside is patience. You wait 3 months for the run to finish. But if there’s no home sale forcing your hand, that wait buys you a far better number. We cover the full process in our guide to long-term radon monitoring in Ontario.
Short-term vs long-term: side by side
Here’s the honest comparison, laid out so you can match the test to your situation.
| Factor | Short-term test | Long-term test |
|---|---|---|
| Run time | 2 to 7 days | 91 days or more |
| What it measures | One short window | A real seasonal average |
| Accuracy | A screen, more weather-sensitive | The number Health Canada trusts most |
| Best for | Home sales, fast peace of mind | The mitigate-or-not decision |
| Season sensitivity | High (test in winter for the safest read) | Low (it averages seasons out) |
| BRF price | $99 flat | $299 |
| Report speed | A few days after pickup | A few days after the 91-day run |
Notice the pattern. Short is fast but noisy. Long is slow but steady. The right pick depends on whether you have a deadline.
Which test should you actually pick?
Match the test to your reason for testing. Here’s the simple decision guide.
Pick a short-term test if:
- You’re buying or selling and need a number before closing.
- You’ve never tested and want a fast first screen.
- You just want to know if there’s a problem worth chasing.
- It’s winter, which gives the most conservative short reading.
Pick a long-term test if:
- You want the most accurate number, full stop.
- A short test came back borderline (around 100 to 200) and you need certainty.
- You’re deciding whether to spend $2,800 to $3,800 on a mitigation system.
- There’s no deadline forcing a fast answer.
A common smart move is to do both, in order. Start with a cheap short-term screen. If it reads high, follow up with a long-term test before you pay for a fix. That way you never spend on mitigation off a single noisy week.
For a fuller walkthrough of timelines, see how long a radon test takes.
DIY kit vs hiring a pro
You can do either test yourself with a mail-in kit, or have a pro handle it. Here’s the honest split, because both are valid.
When DIY makes sense
You own your home. You have no deadline. You just want to know your number.
A DIY long-term alpha-track kit runs about $40. Leave it out for 91 days, mail it in, and wait a couple weeks for the result. It’s a solid number for cheap. The lab uses the same chemistry a pro relies on.
DIY short-term charcoal kits exist too, for around $30. They work for a first screen. Just know that mail-in and lab time add 1 to 2 weeks after the run ends.
When to hire a pro
Some jobs need a certified test with a fast, signed report.
- Buying or selling. A pro short-term or real estate test fits the closing window and gives a report both sides trust.
- Filing a Tarion warranty claim. Tarion needs a proper measurement, not a mail-in slip. See our Tarion warranty guide.
- Confirming a fix worked. The check-up test after a system goes in should be independent.
- A DIY test read high. A second test by a different method removes doubt before you spend.
At Breathe Radon Free, we use continuous monitors for every test. The device drops off, runs, and gets picked up. We write the report. You never make a trip to the post office.
What it costs, plainly
Cost tracks the type of test and who runs it. No surprises here.
- DIY short-term kit: about $30, plus 1 to 2 weeks of mail and lab time.
- DIY long-term kit: about $40, plus a 91-day wait and lab time.
- BRF short-term test: $99 flat, report in a few days.
- BRF real estate test: $399, built for a 48 to 72 hour transaction window.
- BRF long-term test: $299, the most reliable yearly average.
If you want to compare the full menu, our services page lists every option. And our post on what radon levels mean helps you read your result once it’s in.
Radon is the second-leading cause of lung cancer in Canada.
You reach a co-founder here, not a call centre. Every test follows Health Canada protocol.
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Frequently asked questions
Is a short-term or long-term radon test more accurate?
A long-term test is more accurate. It runs 91 days or more and averages out seasonal swings, so it reflects your real yearly exposure. Health Canada considers it the best basis for deciding whether to fix your home. A short-term test is a fast screen, not a final answer.
When is a short-term radon test good enough?
A short-term test is good enough for a first screen or a home sale on a deadline. It tells you fast whether your home is probably fine or probably high. If it reads high or borderline, confirm with a long-term test before you spend on a mitigation system.
Should I test in winter or summer?
Winter gives the most conservative short-term reading. Cold weather and the stack effect pull more radon indoors, so a winter test is less likely to miss a real problem. A long-term test covers both seasons, so timing matters less for it.
Can I use a short-term test to decide on mitigation?
It’s better not to. A single short window can read high or low by chance. Health Canada recommends a long-term test as the basis for the mitigate-or-not call. Use the short test to flag a possible problem, then confirm with a long-term test.
How much does each test cost at Breathe Radon Free?
A short-term residential test is $99 flat. A long-term 91-day test is $299. A faster real estate transaction test is $399. All three follow Health Canada protocol and come with a written report.
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Authored by the Breathe Radon Free Team. Every claim is backed by a primary source. Full bibliography at /sources.
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