There are no short-term symptoms of radon
Radon-222 is a colourless, odourless, tasteless radioactive gas. Unlike carbon monoxide or natural gas, it triggers no headache, no nausea, no dizziness, and no smell. People living in homes with very high radon — well above the Health Canada action level of 200 Bq/m³ — feel completely normal. That is exactly what makes it dangerous: by the time the only "symptom" appears, it is lung cancer.
The real symptom: lung cancer, years later
When radon decays, it produces tiny radioactive particles that lodge in lung tissue. Each decay damages cellular DNA, and that damage accumulates with every year of exposure. Health Canada attributes roughly 3,000 lung-cancer deaths per year in Canada to indoor radon — making it the second leading cause of lung cancer overall and the number-one cause among Canadians who have never smoked.
Lung-cancer symptoms that may eventually appear after years of high exposure include:
- Persistent cough that does not go away
- Coughing up blood
- Chest pain that worsens with deep breathing or coughing
- Hoarseness, wheezing, or shortness of breath
- Frequent respiratory infections like bronchitis or pneumonia
- Unexplained weight loss and fatigue
These symptoms are not specific to radon — they are general lung-cancer warning signs. If you have them, see a physician. But by the time they appear, the underlying damage has already accumulated over many years.
Who faces the highest risk in Canada
Risk depends on three things: the radon level in your home, the number of years you have been exposed, and whether you smoke. Smokers exposed to elevated radon face dramatically higher lung-cancer rates than non-smokers at the same level — the two exposures multiply rather than simply add. Children and stay-at-home adults also tend to accumulate larger lifetime doses because they spend more hours in the home.
Geography matters too. Parts of the Prairies, the Northwest Territories, southern Ontario, Quebec, and New Brunswick have higher-than-average radon. You can look up your postal code on our radon risk page to see the local average from Health Canada data.
What to do if you're worried
Because there are no symptoms to watch for, the only protective step is to test your home. Health Canada recommends a long-term test of at least three months, ideally during the heating season when windows stay closed. A real-time digital monitor will also show you how your levels change with weather and ventilation. If your result is above 200 Bq/m³, mitigation is straightforward and usually costs $2,000–$3,500 in Canada.
Frequently asked questions
Does radon cause immediate symptoms?
No. Radon is colourless, odourless and tasteless, and short-term exposure produces no detectable symptoms. Health effects only appear after years of inhaling elevated levels.
What are the long-term health effects of radon?
Radon is the second leading cause of lung cancer overall and the leading cause among Canadians who have never smoked. Health Canada estimates radon is responsible for roughly 3,000 lung-cancer deaths in Canada every year.
Who is most at risk from radon exposure?
Anyone exposed for many years is at risk, but smokers exposed to high radon face dramatically higher lung-cancer rates than non-smokers at the same level. Children and people who spend more time indoors at home also accumulate higher lifetime doses.
Can I feel radon in my home?
No — you cannot see, smell, or feel radon. The only way to know your level is to test with a long-term radon detector or a real-time digital monitor.
How long does it take for radon to cause harm?
Lung-cancer risk depends on both the radon concentration and the years of exposure. Risk rises substantially with sustained exposure above the Health Canada guideline of 200 Bq/m³.
Keep learning
Long-term test kits vs. real-time digital monitors — what Canadian homeowners should choose.
The 200 Bq/m³ Health Canada guideline, the WHO 100 Bq/m³ reference, and what your reading means.
Sub-slab depressurisation, sealing, and ventilation — typical costs in Canada.
Look up your postal code and see local averages from Health Canada.