Radon Symptoms: What to Watch For (Hint: Almost Nothing)
You can’t smell radon. You can’t see it. You won’t cough, sneeze, or wake up with a headache from it.
That’s the hard truth. People search “radon symptoms” hoping to find a checklist. There isn’t one. Radon gives you no warning at all, which is exactly why it’s the second-leading cause of lung cancer in Canada.
This post is the honest answer to a search that usually starts with worry. We’ll cover what radon actually does, why no one feels sick from it day to day, and what to do instead of looking for signs.
The short version:
- Radon has no short-term symptoms. None. It’s invisible and has no smell.
- The real harm is long-term. Years of exposure raise your lung cancer risk.
- Smokers and ex-smokers face the biggest combined risk by far.
- A basement bedroom, a smoker in the home, or a recent reno are all good reasons to test.
- The only way to know your home’s level is a test. Kits start at $35. Pro tests start at $99.
Why “radon symptoms” is the wrong search
We get it. You read a news story. A friend mentioned it. Maybe a co-worker just found a high reading in their basement.
So you typed “radon symptoms” into Google, hoping you could rule yourself out.
Here’s the truth: there are no symptoms to rule out. Radon doesn’t make you cough. It doesn’t make you tired. It doesn’t make your kids sneeze more. It doesn’t trigger asthma. It doesn’t cause headaches, nausea, or dizziness.
Health Canada is clear on this. Radon has no acute health effects at the levels found in homes.
That’s not reassuring. That’s the problem.
What radon actually does to your body
Radon is a radioactive gas. You breathe it in, and most of it leaves on your next breath.
But some of its decay particles, called radon daughters, stick to dust. That dust lands in your lungs. The particles keep decaying, and each decay shoots a tiny burst of radiation at the tissue right next to it.
Over years, those tiny bursts add up. They damage the DNA in lung cells. Some of those damaged cells turn cancerous.
That’s the whole story. No symptoms. No middle phase where you feel a little off. Just decades of slow damage that ends in lung cancer for some people and never causes a problem for others.
The Canadian Cancer Society estimates radon causes about 3,000 lung cancer deaths in Canada each year.
Why some people feel sick and blame radon
Lots of people in older basements feel a bit off and wonder if radon is to blame.
It almost never is. But basements can make you feel rough for other reasons:
- Mold or damp. Hidden mold behind drywall causes headaches, sinus issues, and fatigue.
- Carbon monoxide. A cracked heat exchanger or old furnace can leak CO. That one really can give you headaches and nausea.
- Poor ventilation. Stale air with high CO2 makes anyone sluggish.
- Dust mites or pet dander. Old finished basements trap a lot of it.
If you feel sick at home, get a CO detector first. Then check for mold. Radon won’t be the cause, but it might still be present.
Bold answer: if you feel sick in your basement, radon is almost certainly not why. Test for it anyway, because the real risk shows up decades later, not today.
Who actually needs to worry
Everyone in Ontario should test their home at least once. That’s the Health Canada line, and it’s the right one.
But some homes carry more risk than others. If any of these match your situation, move the test up your list.
| Situation | Why it matters more |
|---|---|
| Smoker in the home | Smoking plus radon raises lung cancer risk far more than either one alone |
| Kid sleeping in a basement bedroom | 8 to 10 hours a night below grade is the most exposed slot in the day |
| Home is more than 20 years old with a finished basement | More time below grade, more entry points |
| New build (post-2021) | Tighter homes trap more gas, and Tarion may pay to fix it |
| Recent reno that opened the slab | Sumps, drains, and new pipes can create new entry points |
| You’re in Wellington, Halton Hills, Kingston, or the Ottawa Valley | Higher regional averages than the GTA |
Even with none of these, testing is cheap. A $35 long-term mail-in kit gives you a number for the cost of two large pizzas. There’s no good reason to skip it.
The smoker risk multiplier
This is the one number every smoker should hear.
Health Canada and CAREX both estimate that a lifetime non-smoker living in a home at the 200 Bq/m³ guideline has roughly a 1 in 20 chance of developing radon-related lung cancer.
For a smoker in the same home, that risk climbs to about 1 in 3.
The two risks don’t just add. They multiply. The radiation damage and the tobacco damage hit the same cells and the same DNA repair systems. The body can patch one. It can’t keep up with both.
If you smoke or used to, fix two things in parallel: get help to stop, and test your home. The peer-reviewed Ontario data backs both of these as the highest-impact moves you can make.
Common myths to drop
People bring up the same wrong ideas a lot.
- “I’d smell it.” No. Radon is a noble gas with no smell, taste, or colour.
- “My CO detector would alarm.” Different gas. CO alarms don’t see radon at all.
- “It only matters in old homes.” False. The Evict Radon study found post-1980 builds averaged higher than older ones because they’re sealed tighter.
- “My neighbour tested low, so I’m fine.” Two homes a block apart can read 10 times different. Soil, foundation type, and small construction details change everything.
- “I’m at sea level, so radon doesn’t reach me.” Not how it works. Radon comes up from the soil under your slab, not down from the sky.
We bust these and four more in our full post on radon poisoning myths, including why no detector you already own will ever catch radon.
What to do instead of looking for symptoms
Three steps. None of them take long.
1. Test your home. A long-term alpha track kit costs $35 to $60. Order it, leave it in your basement for 91 days, mail it back, and the lab sends you a number in Bq/m³.
2. Read the number. Health Canada’s guideline is 200 Bq/m³.
3. Fix high readings if you have them. A sub-slab depressurization system reduces radon by 80 to 99 percent. It costs $2,800 to $3,800 in Ontario. New build buyers should check our Tarion page first because the builder may owe you the fix at no cost.
DIY vs hire a pro
You can do most of the front end yourself. Some calls need a trained set of eyes.
| Task | DIY is fine | Hire a pro |
|---|---|---|
| Long-term test for general peace of mind | Yes, $35 to $60 kit | Only if you want a faster answer |
| Short-term test for buying or selling a home | No, lab paperwork isn’t accepted | Yes, $99 to $399 |
| Tarion warranty claim test | No, builder requires C-NRPP credentials on the report | Yes, ask if your tester is on the C-NRPP directory |
| Sealing a small visible crack | Yes, with the right caulk | Only if cracks are wide or structural |
| Designing a full mitigation system | No | Yes, proper sub-slab fan sizing matters |
The honest version: a $40 long-term kit beats waiting. We’d rather you spend $40 with someone else than $99 with us if you don’t have a result yet. Once you have a number that needs action, then we can help.
What if you tested high and feel fine
That’s the normal case.
A high test result doesn’t mean damage has already happened. It means the risk is climbing the longer you stay exposed. The fix is straightforward, and you don’t need to panic.
You have time. Days, weeks, even a couple of months to plan a mitigation. What you don’t want is another decade at that level. So get a quote, get the work done, and retest 30 days after install to confirm the fix held.
If you want the deeper science on how radon ends up in homes in the first place, our post on what causes radon gas in homes covers the geology, the stack effect, and the entry points in plain English.
Still wondering how worried to be? Our honest answer to is radon dangerous walks through the actual risk numbers and how radon stacks up against other home hazards.
For more on the broader picture, the Ontario radon guide is a good next read. Or check our FAQ page for the most asked questions.
Frequently asked questions
What are the early symptoms of radon exposure?
There aren’t any. Radon causes no short-term symptoms at the levels found in homes. The harm builds up slowly over years and shows up as lung cancer in some people. If you feel sick at home, the cause is almost always something else, like mold or carbon monoxide.
Can radon cause headaches, fatigue, or nausea?
No. Those symptoms point to other indoor air problems, not radon. Get a CO detector and check for hidden mold. Test for radon too, but don’t expect a high reading to explain how you feel today.
How long does it take for radon to make you sick?
There’s no acute illness from home-level radon. The lung cancer risk builds over decades of exposure. Smokers see the risk rise faster because the two effects multiply. Children in basement bedrooms accumulate exposure over a longer window than adults moving in later.
Can a radon test tell you if you’re already at risk?
A test tells you the level in your home right now. It doesn’t tell you what’s happening in your lungs. If you’re worried about cancer risk specifically, talk to your doctor. They may suggest a low-dose CT scan if you have other risk factors like a smoking history.
Should I test even if no one in my house feels sick?
Yes. The whole point is that you won’t feel sick. Health Canada recommends every home in Canada be tested at least once. The kits cost less than a tank of gas, and the answer lasts you a decade.
Authored by the Breathe Radon Free Team. Every claim is backed by a primary source. Full bibliography at /sources.
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