Best Radon Testing & Mitigation in St. Thomas

About Radon in St. Thomas, Ontario

Last updated: March 2026

St. Thomas is served by C-NRPP certified radon professionals listed on RadonFinder.ca. Ontario has widely varying radon risk depending on geography. The Ottawa Valley, eastern Ontario, and areas underlain by the Canadian Shield, including parts of Sudbury, Elliot Lake, and the Bancroft region, have elevated radon due to uranium-rich granite bedrock. Southern Ontario's clay and limestone geology generally produces lower levels, though local hotspots exist in any region. Health Canada estimates roughly 7% of Ontario homes exceed the guideline.

Typical Mitigation Cost in Ontario

$2,200–$3,800

Near national average

Costs vary significantly between the GTA, Ottawa, and northern Ontario due to labour markets and home construction types.

  • •Foundation type: poured concrete, block, or slab
  • •Basement finish level: unfinished installs are faster and cheaper
  • •Pipe routing complexity in finished or split-level homes
  • •GTA vs. rural Ontario labour rate differences
  • •Age of home: older homes may require additional sealing work

Showing 1–3 of 3 professionals in St. Thomas

Doug Tarry Homes

St. Thomas, ON
4.6(49)Google

Doug Tarry Homes is a C-NRPP certified radon testing professional serving St. Thomas, ON and across ON. Their certified inspectors provide accurate radon measurements for homes and businesses.

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Radon Checks

St Thomas, ON

Radon Checks is a C-NRPP certified radon testing professional serving St Thomas, ON. Their certified inspectors provide accurate radon measurements for homes and businesses.

Testing
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EXP Service Inc.

London, ON
4.2(11)Google

EXP Service Inc. is a C-NRPP certified radon testing and mitigation professional serving London, ON. They offer complete radon solutions from initial testing through to mitigation system installation.

TestingMitigation
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Frequently Asked Questions: Radon in St. Thomas

RadonFinder.ca lists C-NRPP certified radon testing and mitigation professionals serving St. Thomas, Ontario. Browse the directory above to compare professionals by services offered, certifications, and reviews.
Most homeowners in Ontario pay between $2,200 and $3,800 for a complete radon mitigation system. Actual cost depends on your foundation type, home size, and the complexity of the installation. Request quotes from multiple professionals to compare.
St. Thomas follows Health Canada's national guideline of 200 Bq/m³. If your home tests above this level, Health Canada recommends taking action to reduce radon within two years for levels between 200 and 600 Bq/m³, and within one year if above 600 Bq/m³.
Yes. Health Canada recommends testing every home in Canada, regardless of age, construction type, or location. Radon levels vary from house to house and even neighbouring homes can have very different readings. A long-term test of at least 91 days during the heating season is the most reliable method.
The most common system is active sub-slab depressurization (ASD). A certified professional installs a pipe through your foundation slab connected to a fan that draws radon from beneath the home and vents it safely above the roofline. Installation typically takes one day.

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Radon Resources for St. Thomas

Tools and guides to help you understand radon risk and take action.

Check your radon risk
Estimate your risk based on province, home age, and foundation type.
Understand your test results
Learn what Bq/m³ means and when action is required.
DIY radon test kits
Compare test kit options starting from $10.
Radon guides & articles
In-depth guides on testing, mitigation, and health risk.
Browse all provinces
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Radon FAQ
Answers to the most common questions about radon.