What is radon? A plain-language guide for Ontario homeowners
Radon is a radioactive gas from uranium in soil and rock. Learn where it comes from, why it builds up in Ontario basements, and how to find out your level.
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Learn about radon
Straight answers about radon in Ontario homes
What it is, why Health Canada changed the rules in 2007, how to test, what your number means, and how it’s fixed. Written for homeowners, sourced to Health Canada and peer-reviewed research.
Why the guideline dropped from 800 to 200
If your home was tested before 2007, this is for you.
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Why Health Canada lowered the radon guideline from 800 to 200 Bq/m³
In 2007 Canada cut its radon guideline by 75%, from 800 to 200 Bq/m³. Here’s why it changed, what it means for homes tested before then, and what to do now.
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Health Canada vs the EPA vs the WHO: which radon level should you act on?
Canada acts at 200 Bq/m³, the U.S. EPA at 148 and the WHO prefers 100. Why they differ, and what to do if your result falls between 100 and 200.
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Nine radon myths we hear in Southern Ontario
“We’re not on the Shield.” “My neighbour tested fine.” “New homes don’t get radon.” Common radon myths in Southern Ontario, and the facts.
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Health and risk
Radon and lung cancer: what the risk really is
Radon causes about 16% of lung cancer deaths in Canada. How radon damages the lungs, how smoking multiplies the risk, and why long-term exposure is what counts.
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When is radon dangerous? Levels, time and who is most at risk
What radon level is dangerous, how long exposure matters, which rooms and people face the most risk, and how Health Canada’s action timelines work.
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How radon gets into your home (and why winter makes it worse)
The stack effect, entry points and soil conditions that pull radon into Ontario homes, and why levels peak in winter and on the lowest floor.
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Damage, age and life stage
How radon damage works, and why it can’t be undone
Radon harm builds silently over years. How inhaled radon decay products damage lung cells, why that damage is permanent, and what lowering radon does and doesn’t change.
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Radon risk by age: babies, children, adults and older adults
What is known, and not known, about radon risk at each age. Why babies and children get extra attention, what changes for older adults, and what to do at each stage.
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Before you bring a baby home: a radon-first home safety checklist
A checklist for expecting parents in Ontario: test for radon early enough to fix it before the baby comes home, plus the other home safety checks.
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Radon and older adults: what to check at home, with a checklist
A radon-first home checklist for older adults and their families: where to test, basement suites, downsizing moves and renovations.
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Testing
How to test for radon in Ontario: long-term, short-term, DIY or professional
Step-by-step radon testing to Health Canada protocol: which test to use, where to put it, how long to run it, and when a professional test is worth it.
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How to read your radon test results (Bq/m³ and pCi/L)
Enter your radon result and see what it means. Health Canada’s action levels, converting pCi/L to Bq/m³, short-term vs long-term results, and next steps.
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Radon when buying or selling a home in Ontario
How Ontario buyers and sellers handle radon: tests that fit a conditional period, holdbacks and price adjustments, and why a fixed home sells well.
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Fixing it
How radon mitigation works: sub-slab depressurization explained
How an active soil depressurization system removes radon, what gets installed, how long it takes, what it costs to run, and how to know it’s working.
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How much does radon mitigation cost in Ontario?
Typical radon mitigation and testing costs in Ontario, what drives the price up or down, running costs, and how to compare quotes.
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Radon in new homes: the 2024 Ontario Building Code, rough-ins and Tarion
What the 2024 Ontario Building Code requires for radon, what a rough-in does (and doesn’t do), Tarion’s radon warranty, and why new homes still need testing.
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Tools
Check a result, convert units, look up a term
Enter a number to see what it means.
Health Canada’s guideline is 200 Bq/m³, based on a long-term test of at least three months.
Radon glossary
Bq/m³, pCi/L, stack effect, rough-in, C-NRPP and 30 more terms in plain language.
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Radon FAQ
Quick answers about testing, mitigation, costs, new homes and real estate.
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Radon by area
What’s known about the ground and homes in your town, from Windsor to Brantford.
Find your area
Know your number in one heating season.
Book a radon test with a C-NRPP certified technician: an early reading at 2 weeks, the full result at 91 days. If it’s high, we’ll design a fix and prove it worked.