Radon Exposure in Southern Ontario Homes
The Invisible Health Risk Every Homeowner Should Know
When homeowners think about indoor air quality, they often focus on mold, dust, or allergens. However, one of the most significant health risks inside Canadian homes is something you can't see, smell, or taste—radon gas.
Across Southern Ontario, thousands of homes have elevated radon levels, yet many homeowners remain unaware of the danger. The good news is that testing is simple, affordable, and can provide peace of mind for you and your family.
What Is Radon?
Radon is a naturally occurring radioactive gas produced by the breakdown of uranium in soil and rock. As it forms underground, it moves through the soil and can enter homes through:
Foundation cracks
Basement floor joints
Sump pits
Utility penetrations
Crawl spaces
Gaps around pipes and drains
Once inside, radon can accumulate to dangerous levels, especially during the colder months when homes are tightly sealed.
Because radon has no colour, odour, or taste, the only way to know if your home has elevated levels is through testing.
Why Is Radon Dangerous?
Radon is the second leading cause of lung cancer after smoking and the leading cause among non-smokers.
When radon gas is inhaled, radioactive particles become trapped in the lungs. Over time, these particles damage lung tissue and significantly increase the risk of developing lung cancer.
Health experts estimate that radon contributes to over 3,000 lung cancer deaths each year in Canada.
The risk increases with:
Long-term exposure
Higher radon concentrations
Smoking or previous smoking history
However, even people who have never smoked can develop lung cancer from prolonged radon exposure.
Is Radon a Problem in Southern Ontario?
Yes.
Many homeowners mistakenly believe radon is only a concern in northern or mountainous regions. In reality, elevated radon levels have been found throughout Southern Ontario.
Communities where elevated radon has been identified include:
London
Kitchener-Waterloo
Guelph
Cambridge
Hamilton
Niagara Region
Simcoe County
Barrie
Orangeville
Durham Region
Peterborough
Ottawa Valley
Even neighbouring homes can have dramatically different radon levels because of variations in soil porosity, foundation construction, and ventilation.
Your neighbour's test results cannot predict the radon level in your home.
Which Homes Are Most at Risk?
A common misconception is that only older homes have radon problems.
In reality, any home can have elevated radon levels, regardless of:
Age
Size
Foundation type
Construction quality
Whether the home has a finished basement
In fact, newer homes can sometimes have higher radon concentrations because modern construction techniques create tighter, more energy-efficient buildings that reduce natural air exchange. The good news, if you've bought a new home directly from a builder in the last 7 years, you may be covered under the Tarion Home Warranty for full reimbursement on a radon mitigation system. If you'd like help applying for coverage under the Tarion Home Warranty, contact Radon River and our experts would be happy to walk you through the process.
Health Canada Guidelines
Health Canada recommends taking action if radon levels are 200 Bq/m³ or higher.
General recommendations include:
Below 200 Bq/m³: Continue monitoring every few years or after major renovations.
200–600 Bq/m³: Reduce radon levels within two years.
Above 600 Bq/m³: Reduce radon levels within one year.
There is currently no completely risk-free level of radon exposure, meaning lower concentrations are always preferable. The best thing you can do is test in order to make an educated decision on a radon mitigation system.
How Is Radon Tested?
The most reliable method is a long-term radon test, typically lasting at least 90 days during the heating season (October through April).
Long-term testing provides a much more accurate picture of average radon exposure than short-term tests, which can be affected by weather and changing ventilation conditions.
Professional radon testing services use calibrated equipment and follow C-NRPP testing protocols to ensure accurate results.
What Happens If Your Home Has High Radon Levels?
Fortunately, elevated radon can be reduced effectively.
The most common solution is an active sub-slab depressurization system, which uses a specialized pipe and continuously operating fan to safely vent radon gas outside before it enters the home.
Our professionally installed radon mitigation systems can often reduce radon concentrations by 80–99%, depending on the home's construction.
Should Home Buyers Test for Radon?
Absolutely.
A home inspection evaluates many visible aspects of a property, but radon cannot be detected during a visual inspection.
If you're purchasing a home in Southern Ontario, radon testing should be considered an important part of understanding the property's environmental health.
Likewise, existing homeowners should consider testing every few years or after major renovations that affect the home's foundation or ventilation.
Radon River offers expedited results on short term radon gas testing, specifically for real estate transactions.
Protecting Your Family Starts with One Simple Test
Radon is one of the few serious health risks in your home that is both easy to identify and highly treatable.
Because elevated radon levels can occur in virtually any neighbourhood across Southern Ontario, testing is the only reliable way to know whether your home is safe.
Whether you've lived in your home for decades or recently purchased a new property, a professional radon test is a small investment that can make a lasting difference to your family's health.
If you haven't tested your home yet, now is the perfect time. Knowing your radon level today could help protect your family's health for years to come.