Radon Poisoning: What's Real, What's Myth
Canadians search “radon poisoning” hundreds of times a month. Here’s the thing: it doesn’t exist.
Not the way you’re picturing it, anyway. There’s no sudden sickness. No fumes that knock you out. No ER visit for a bad radon day.
And yet radon is still the second-leading cause of lung cancer in Canada.
This post sorts out what’s real and what isn’t. No scare tactics. Just the evidence.
The short version:
- “Radon poisoning” isn’t a real diagnosis. There’s no acute sickness from radon at home levels.
- The real risk is slow. Years of breathing radon raise your lung cancer odds.
- You can’t smell it, and no CO or smoke alarm will ever detect it.
- It’s not only a basement problem, and new homes often test higher than old ones.
- The only way to know your level is a test. Kits cost about $35. A pro test is $99.
Why “radon poisoning” is the wrong name
Poisoning means a dose that makes you sick fast. Carbon monoxide does that. So do bad mushrooms.
Radon doesn’t work like that. There’s no acute radon sickness at the levels found in homes.
Radon is a radioactive gas that seeps up from the soil. You breathe it in, and most of it leaves on your next breath. The harm comes from its decay particles, which stick to dust, land in your lungs, and fire tiny bursts of radiation at the tissue around them.
One day of that does nothing you’d ever notice. Twenty years of it raises your odds of lung cancer. That’s the real risk: slow, silent, and cumulative.
So when you see “radon poisoning symptoms” lists online, be skeptical. We wrote a full post on why radon has no symptoms at all.
The 7 myths, sorted
Here’s the quick scorecard before we go through each one.
| Myth | Reality |
|---|---|
| ”Radon poisoning makes you sick with headaches or nausea” | False, no acute symptoms at home levels |
| ”I’d smell it or see it” | False, no smell, no taste, no colour |
| ”My CO or smoke detector would catch it” | False, they can’t detect radon at all |
| ”It’s only a basement problem” | Mostly true, but main floors read high too |
| ”New homes don’t have radon” | False, newer homes often test higher |
| ”Opening windows fixes it” | Temporary at best, levels rebound in hours |
| ”My neighbour tested low, so I’m fine” | False, homes a block apart can read 10x different |
Now the detail on each.
Myth 1: radon poisoning has symptoms
People expect headaches, nosebleeds, fatigue, or nausea. None of those come from radon.
Health Canada is direct about this: radon has no short-term health effects at the levels found in homes.
Radon’s only known health effect is lung cancer, and it takes years of exposure to build that risk.
Myth 2: you’d smell it or see it
Radon is a noble gas. No smell. No taste. No colour.
That “rotten egg” smell some people mention? That’s sulphur compounds in sewer gas or well water. Different problem. A musty basement smell is humidity and mold, not radon.
A home can sit at 10 times the Canadian guideline and the air feels completely normal.
Myth 3: your CO or smoke detector would catch it
This one trips up a lot of careful homeowners. You’ve got a CO alarm on every floor, so you figure you’re covered.
You’re not. CO detectors sense carbon monoxide. Smoke alarms sense smoke particles. Neither can see radon, and no combination unit on the market adds it.
Radon needs its own device: a mail-in test kit or a digital radon monitor. Nothing else in your home will ever warn you.
The most dangerous myth is the detector one. Families with every safety gadget installed still have zero radon coverage unless they’ve run an actual radon test.
Myth 4: it’s only a basement problem
This one is mostly true, and that’s exactly why it misleads people.
Radon enters from the soil, so the lowest level reads highest. But it doesn’t stay there. As a rough rule, the main floor reads about half the basement level, and the second floor about a quarter.
So a basement at 800 Bq/m³ can mean a main floor around 400. That’s still double the Canadian guideline of 200 Bq/m³.
The rule that matters: test the lowest level where someone spends 4 or more hours a day.
Myth 5: new homes don’t have radon
Plenty of buyers assume radon is an old-house problem, like knob-and-tube wiring.
The data says the opposite. The Evict Radon national study found homes built after 1980 average higher radon than older ones.
There’s a silver lining for new-home owners in Ontario. If your home was built after February 2021 and tests above the guideline, Tarion warranty coverage can make your builder pay for the fix, up to $50,000. Our Tarion page walks through it.
Myth 6: opening windows fixes it
Open windows do drop radon levels. For a few hours.
Close them, and the level climbs right back, usually within half a day. You can’t ventilate your way out of a radon problem in a Canadian winter. Nobody keeps windows open in January in Ontario.
The fix that actually works is a sub-slab depressurization system. A pipe and fan pull soil gas from under your foundation and vent it outside, cutting indoor levels by 80 to 99 percent.
Myth 7: your neighbour’s test covers you
Two houses on the same street can read 10 times apart.
Health Canada’s Cross-Canada Survey found big swings between homes in the same community.
A radon map or a neighbour’s result tells you about regional odds. It tells you nothing about your house. Only your own test does that.
What the evidence actually shows
Strip away the myths and the real picture is simple.
- Radon causes about 3,000 lung cancer deaths in Canada each year.
- It’s the top cause of lung cancer in people who’ve never smoked.
- A lifetime non-smoker in a home at 200 Bq/m³ carries roughly a 1 in 20 chance of radon-related lung cancer. For a smoker, it’s about 1 in 3.
- About 7 percent of Canadian homes sit above the guideline, and the only way to find out is testing.
Serious, yes. An emergency, no. Even a high reading gives you months to plan a fix.
DIY vs hire a pro
Most of the radon journey is a do-it-yourself job. Here’s the honest split.
| Task | DIY is fine | Hire a pro |
|---|---|---|
| Long-term test for peace of mind | Yes, $35 to $60 kit | Only if you want a faster answer |
| Short-term test for a real estate deal | No, the other side won’t accept it | Yes, $99 to $399 |
| Tarion warranty claim test | No, the report needs certified credentials | Yes, check the C-NRPP directory |
| Sealing small visible cracks | Yes, with the right caulk | Only if cracks are wide or structural |
| Full mitigation system design | No | Yes, fan sizing and pipe routing matter |
The honest version: start with a $35 long-term kit from a hardware store or Take Action on Radon.
If your number comes back high, or you’re on a real estate or warranty deadline, that’s when a pro test makes sense. Ours is $99 flat.
What to do with this
Three steps, none of them scary.
1. Drop the symptom watch. You’ll never feel radon. Stop checking how you feel and get a number instead.
2. Test your home. A long-term kit costs about $35 and runs 91 days. Health Canada recommends every home in Canada test at least once.
3. Act on the number. Under 100 Bq/m³, retest in five years. Between 100 and 200, retest long-term. Over 200, plan a mitigation. Our guide to what radon levels mean covers every range.
Got more questions? Our FAQ page answers the most common ones in plain English.
Frequently asked questions
Is radon poisoning real?
Not as an acute illness. There’s no sudden sickness from breathing radon at home levels, and “radon poisoning” isn’t a medical diagnosis. The real risk is long-term: years of exposure raise your chance of lung cancer. That’s why testing matters even though nobody feels sick.
What are the symptoms of radon poisoning?
There aren’t any. Radon causes no headaches, nausea, fatigue, or breathing trouble at the levels found in homes. If you feel unwell at home, check carbon monoxide and mold first. The only health effect linked to radon is lung cancer, which develops over decades.
Will a carbon monoxide detector detect radon?
No. CO detectors and smoke alarms can’t sense radon at all. Radon needs its own test: a mail-in kit, a digital radon monitor, or a professional measurement. No standard home safety device covers it.
Can you get radon poisoning from one exposure?
No. A day, a week, or even a year in a high-radon home won’t make you sick. The risk builds slowly over many years of exposure, which also means a high test result isn’t an emergency. You have time to fix it properly.
How do I know if my home has radon?
Test it, that’s the only way. A long-term kit costs about $35 and runs 91 days. A professional short-term test costs $99 and takes about a week. Maps, neighbours’ results, and the age of your home can’t tell you what’s in your air.
Authored by the Breathe Radon Free Team. Every claim is backed by a primary source. Full bibliography at /sources.
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