Radon in Ottawa: Levels, Risk Areas & What to Do

Ottawa has a radon problem that catches most residents off guard. The city-wide average sits around 85 Bq/m³, and roughly 1 in 6 Ottawa-Gatineau area homes exceeds Health Canada's action level of 200 Bq/m³. That's well above the Ontario provincial average of about 1 in 14. The cause is geology, and it varies significantly by neighbourhood.

Ottawa's radon levels by the numbers

Ottawa sits at an uncomfortable position in Ontario's radon landscape. The provincial average is approximately 7% of homes above 200 Bq/m³. Ottawa-Gatineau runs closer to 17%. That gap matters.

To put it in context:

• Ottawa-Gatineau area average: approximately 85 Bq/m³
• Homes above 200 Bq/m³: roughly 1 in 6
• Ontario province average: approximately 1 in 14
• National average indoor level: approximately 25 Bq/m³

Ottawa homeowners face meaningfully higher risk than the provincial numbers would suggest. If you've been assuming your home is probably fine because you're in Ontario, it's worth revisiting that assumption.

Why Ottawa has elevated radon

The Ottawa region sits on a particularly varied geological foundation. A 2016 geological study of the National Capital Region mapped radon risk by bedrock type across the city's neighbourhoods. The eastern part of the city overlies formations of the Canadian Shield, including uranium-bearing Precambrian rock and sedimentary units that produce radon at higher rates than southern Ontario's clay-rich geology.

A 2016 geological study of the National Capital Region mapped radon risk by bedrock type, identifying specific formations as higher risk: the Billings Formation, the Eastview member of the Lindsay Formation, and portions of the Bobcaygeon Formation, all of which contain elevated uranium concentrations. These formations run through much of eastern and central Ottawa, producing soil gas that migrates upward into homes.

The Ottawa Valley beyond the city proper has an even longer history of elevated radon. Studies of the Valley corridor, which runs northeast along the Ottawa River, have found rates well above 10% of homes exceeding 200 Bq/m³ in some communities.

Which Ottawa neighbourhoods carry the highest risk

This is where Ottawa's radon story gets specific. The city has unusually well-documented neighbourhood-level risk mapping thanks to geological surveys of the National Capital Region. The broad pattern:

Higher risk areas:

• Orleans and Gloucester (eastern Ottawa)
• Blackburn Hamlet
• Bells Corners
• Southern Barrhaven
• Centretown, The Glebe, and Old Ottawa South
• Nepean
• Richmond and North Gower

Moderate risk areas:

• Most of Kanata and Stittsville
• Northern Barrhaven
• Carp and South March

Kanata, which sits on younger glacial deposits west of the Gatineau Hills, tends to run lower than eastern Ottawa. Orleans and Gloucester, underlain by Canadian Shield rock, consistently show elevated readings.

One important caveat: these are probability maps, not guarantees. Two houses on the same street can have dramatically different readings based on foundation type, how well-sealed the home is, and the specific soil conditions directly beneath each house. A home in Kanata can test above 200 Bq/m³, and a home in Orleans can test below 100 Bq/m³. The neighbourhood tells you the odds, not your result.

The only way to know your home's level is to test it.

How to test your Ottawa home

Health Canada recommends a long-term alpha track test, a small device placed in the lowest livable area of your home for at least 91 days. The heating season (October through April) gives the most accurate result since homes are sealed and radon concentrations are at their highest.

Option 1: Long-term mail-in test kit (~$30–$60)

The most accurate approach for making decisions about mitigation. Place the device, leave it for 91+ days, mail it to the lab. Results arrive within a couple of weeks. This is what Health Canada recommends for any mitigation decision.

Option 2: Electronic continuous monitor (~$160–$350)

Gives live readings and tracks levels over time. Useful for ongoing monitoring or for checking levels after a mitigation system is installed. C-NRPP approved models include the Airthings Corentium Home, Aranet RN+, and Ecosense RadonEye. Leave in place for at least 90 days before relying on the long-term average.

Place your test on the lowest floor you regularly use. Basement if you have one; main floor if you don't. Keep it away from exterior walls, windows, and vents.

For a full walkthrough of placement and timing, see: How to test your home for radon.

What to do if your Ottawa result is high

Given Ottawa's city-wide average of around 85 Bq/m³, many homeowners will find their results between 100 and 200. That's not a crisis, but it warrants a decision: run a follow-up long-term test to confirm, or consult a certified professional about whether mitigation makes sense for your home and household.

If your result is at or above 200 Bq/m³, the standard fix is sub-slab depressurization. A contractor drills through your foundation slab, installs PVC piping, and connects it to a fan that runs continuously. The fan draws radon from beneath your foundation and vents it outside before it can enter the home. Most systems reduce levels by 80–99% and can be installed in a single day.

For more on what your result means: How to interpret your radon test results.

Radon in Ottawa real estate

Ottawa's real estate market is one of the most active in Canada, driven by federal government employment, military bases, and a large post-secondary student population. Radon is increasingly showing up in home transactions here.

Given the city's elevated risk profile, including radon testing as a condition of purchase is reasonable in any Ottawa transaction. If you're buying in Orleans, Gloucester, or Nepean, it's especially worth making it a standard part of your inspection conditions. Short closing timelines call for professional continuous monitoring (results in 48–96 hours) rather than a 91-day mail-in test.

Sellers who have already tested and mitigated are in a good position. A documented result above 200 Bq/m³ with a subsequent professional mitigation and post-test confirmation can be presented as a feature, not a liability. Buyers who understand radon often prefer a home with a known, solved problem over one that's never been tested.

For more on how to handle radon in a transaction: Radon and real estate in Canada.

What mitigation costs in Ottawa

Ottawa sits roughly at the national average for mitigation costs. Most Ottawa homeowners pay between $1,500 and $3,000 for a standard sub-slab depressurization system. Complex foundations, finished basements with difficult pipe routing, or homes requiring multiple suction points can push costs higher.

Ottawa has a reasonably strong contractor market compared to smaller Ontario cities, which tends to keep pricing competitive. Getting two or three quotes is worth the time.

For a full cost breakdown: How much does radon testing and mitigation cost in Canada?

Find a certified radon professional in Ottawa

Every professional listed on RadonFinder.ca holds active C-NRPP certification, the national standard recognized by Health Canada. C-NRPP certified professionals have completed specific training in radon measurement and mitigation and are qualified to assess your home and install a system that meets Canadian standards.

Browse certified radon professionals serving Ottawa

When contacting a contractor, ask whether they're C-NRPP certified for both testing and mitigation (some hold one certification but not both), whether post-mitigation testing is included in the quote, and what warranty they offer on the installed system.

Most Ottawa-area contractors can schedule consultations within a week or two, with installation shortly after.

The bottom line

Ottawa's radon risk is meaningfully higher than most Ontario residents expect, and it varies enough by neighbourhood that you can't assume your home is safe based on where you live. The eastern parts of the city, Orleans, Gloucester, and Blackburn Hamlet in particular, carry above-average risk. But elevated readings show up across the city.

Testing takes 91 days and costs $30–$60. It's the only way to know what's actually in your home's air.

• Browse DIY radon test kits and monitors
• Find a certified radon professional in Ottawa
• Check Ontario's radon risk profile