Homes at or above the guideline
12.4
%Share of properties in Ontario with radon at or above 200 Bq/m³ in the 2024 Cross-Canada Radon Survey (weighted by building type).
- Date
- 2024-10-01
- Sample
- weighted by building type
Province or territory
Radon in Ontario
Radon levels in Ontario homes and where they are highest, from the 2024 survey by census division, with certified providers, funding and rules, dated.
Photo: Ian Furst, CC BY-SA 3.0, cropped, via Wikimedia Commons.
Canadian homes at or above the guideline
17.8
%Share of single-detached, semi-detached and row properties in Canada with radon at or above 200 Bq/m³ in the 2024 Cross-Canada Radon Survey.
- Date
- 2024-10-01
- Sample
- 69,478 long-term tests
Certified providers
86
Businesses with a business address in Ontario and at least one active C-NRPP credential, as of 2026-10-18.
- Date
- 2026-10-18
- Sample
- Not applicable
Share of properties at or above 200 Bq/m³ by survey reporting unit, Ontario
- 5% or less
- over 5% to 10%
- over 10% to 20%
- over 20% to 30%
- over 30% to 40%
- over 40%
- No data
- Insufficient data
Each census division shows the figure for its reporting unit, so every division in a pooled unit takes the pooled figure. Divisions the report lists with no data or fewer than four readings are marked.
Source: Cross-Canada Survey of Radon Exposure in the Residential Buildings of Urban and Rural Communities, 2024 Report, Version 1.1 (CCSR.24.1.1), released October 2024, ISSN 2818-8195. Cross-Canada Survey of Radon working group. Boundaries: Statistics Canada, 2021 Census census-division cartographic boundary file, adapted. Not an endorsement by Statistics Canada.
Radon by census division
Survey reporting units in Ontario, 2024 Cross-Canada Radon Survey
| Reporting unit | Readings | At or above 200 Bq/m³ (%) | Geometric mean (Bq/m³) | Highest observed (Bq/m³) |
|---|---|---|---|---|
| Bruce | 43 | 14 | 62 | 718 |
| Chatham-Kent | 44 | 20.5 | 109.7 | 1,092 |
| Dufferin | 74 | 10.8 | 66.7 | 489 |
| Durham | 114 | 6.1 | 41.9 | 416 |
| Elgin | 185 | 2.7 | 58.3 | 528 |
| Essex | 145 | 14.5 | 99.3 | 548 |
| Frontenac | 214 | 23.4 | 74.8 | 847 |
| Grey | 63 | 20.6 | 73.8 | 2,756 |
| Haldimand-Norfolk; Brant (pooled) | 50 | 10 | 76.1 | 476 |
| Halton | 230 | 9.6 | 66.3 | 1,013 |
| Hamilton | 1,011 | 12.8 | 71.6 | 2,473 |
| Hastings | 56 | 21.4 | 67.3 | 600 |
| Huron | 27 | 11.1 | 89.9 | 665 |
| Kawartha Lakes; Muskoka; Haliburton (pooled) | 45 | 11.1 | 65.7 | 492 |
| Lambton | 42 | 19 | 86.7 | 567 |
| Lanark | 114 | 42.1 | 137.6 | 1,464 |
| Leeds and Grenville | 220 | 31.4 | 113 | 3,165 |
| Lennox and Addington | 38 | 44.7 | 130.7 | 430 |
| Manitoulin (no data) | 0 | no data | no data | no data |
| Middlesex | 139 | 4.3 | 63.8 | 664 |
| Niagara | 95 | 11.6 | 62.9 | 857 |
| Nipissing; Parry Sound (pooled) | 30 | 10 | 60 | 471 |
| Northumberland | 39 | 15.4 | 37.7 | 349 |
| Ottawa | 1,349 | 12 | 72.8 | 1,889 |
| Oxford | 27 | 18.5 | 92.5 | 1,144 |
| Peel | 113 | 4.4 | 45.5 | 557 |
| Perth | 33 | 21.2 | 87.3 | 746 |
| Peterborough | 60 | 18.3 | 73.9 | 2,809 |
| Prescott and Russell | 71 | 9.9 | 61.3 | 840 |
| Prince Edward | 85 | 27.1 | 102.1 | 551 |
| Rainy River; Kenora (pooled) | 32 | 43.8 | 156.3 | 448 |
| Renfrew | 192 | 29.2 | 106.1 | 946 |
| Simcoe | 150 | 4.7 | 46.3 | 733 |
| Stormont, Dundas and Glengarry | 28 | 3.6 | 53.1 | 216 |
| Sudbury; Greater Sudbury / Grand Sudbury; Timiskaming; Cochrane; Algoma (pooled) | 60 | 13.3 | 86.1 | 1,799 |
| Thunder Bay | 896 | 34.8 | 132.6 | 32,321 |
| Toronto | 387 | 1.3 | 40.3 | 358 |
| Waterloo | 258 | 10.5 | 72.3 | 1,009 |
| Wellington | 798 | 12.7 | 71.2 | 940 |
| York | 177 | 4 | 37.5 | 369 |
Cross-Canada Survey of Radon Exposure in the Residential Buildings of Urban and Rural Communities, 2024 Report, Version 1.1 (CCSR.24.1.1), released October 2024, ISSN 2818-8195. Cross-Canada Survey of Radon working group.
Cities with a page
Survey municipalities in Ontario
| City | Census division | At or above 200 Bq/m³ (%) | Providers with an address here |
|---|---|---|---|
| Centre Wellington | Wellington | 8 | 0 |
| Guelph | Wellington | 13.5 | 2 |
| Hamilton | Hamilton | 12 | 2 |
| Kingston | Frontenac | 23.7 | 1 |
| Kitchener | Waterloo | 10.2 | 3 |
| London | Middlesex | 3.5 | 5 |
| Ottawa-Gatineau | Ottawa | 17 | 9 |
| Thunder Bay | Thunder Bay | 34.3 | 5 |
| Toronto | Toronto | 4.5 | 2 |
| Windsor | Essex | 14.5 | 1 |
C-NRPP, Find a Professional directory: every province and territory searched for each of the six service types, de-duplicated by the registry's person id. Pulled on 2026-10-18.
Help paying for radon testing or mitigation in Ontario
Grant
Lungs Matter radon mitigation grant
Up to $1,500 toward home radon mitigation. Radon is named as eligible. Current. As of 2026-09-01.
Forgivable loan
Ontario Renovates
Varies by service manager, roughly $15,000 to $25,000. Radon is not named. Varies by service manager.. As of 2026-09-18.
Warranty coverage
Tarion new home warranty, radon coverage (FH 1.19)
Up to $50,000 where the Agreement of Purchase and Sale was signed after 1 February 2021, otherwise $15,000. Radon is named as eligible. Current for qualifying homes.. As of 2026-09-18.
Free or subsidized testing
100 Radon Test Kit Challenge
Radon is named as eligible. Current. As of 2026-09-18.
Radon rules in Ontario
Laws, codes and decisions on radon that apply in Ontario
Each row names its instrument and status as the authority states it. Guidance is not law; a tribunal decision is not court precedent. Canada's 200 Bq/m³ guideline binds no homeowner.
| Rule type | Applies to | What it says | Instrument | Status | In effect from |
|---|---|---|---|---|---|
| Building code | Ontario | Ontario's current code came into force 1 January 2025 and revoked the 2012 code. New houses require a rough-in for a subfloor depressurization system, and all permit applications from 1 April 2025 must use the 2024 code; the building officials' association says a sub-slab depressurization rough-in is required for all Part 9 residential uses, along with a separate membrane air barrier. The 2012 code applied radon provisions only where radon was "known to be a problem"; that rule is historical, though it still governs some transition projects. | O. Reg. 163/24: Building Code (adopting the National Building Code 2020 with Ontario amendments) | In force | 2025-01-01 |
| Real estate disclosure | Ontario | Sellers must disclose known latent defects that make a home unsafe, and TRESA Phase 2 put separate disclosure duties on agents. The Seller Property Information Statement is voluntary, and its environmental question names radon gas as an example. | Trust in Real Estate Services Act, Phase 2 (in force 1 December 2023); OREA Seller Property Information Statement (voluntary) | In force | 2023-12-01 |
| Rental housing | Ontario | The tribunal held that radon above Health Canada's guideline breached the landlord's duty to keep the unit in good repair. A tenancy tribunal decision, not court precedent. | Landlord and Tenant Board, CET-67599-17 (Re), 2017 CanLII 60362 | Tribunal or court decision | no data |
| New home warranty | Ontario | Radon in a new home shall not exceed 200 Bq/m³. Repairs are required where a long-term test of 91 days or more, conducted in the lowest level, exceeds 200 Bq/m³ and the exceedance results from a Building Code violation or a defect in the builder's work or materials. Coverage runs one year for workmanship and materials, two years for Code health and safety violations and seven years for major structural defect, and stays with the home for seven years from original possession. Up to $50,000 where the purchase agreement was signed after 1 February 2021, otherwise $15,000. An approved do-it-yourself kit or a certified professional may run the test. | Tarion Construction Performance Guidelines, 5th Edition, article FH 1.19 Radon Exceeds Acceptable Levels (added 24 May 2024; process in effect since 2013) | In force | 2024-05-24 |
| Workplace | Ontario | Ontario applies the Canadian NORM Guidelines to all workplaces through its general duty clause and tells employers to reduce radon below 200 Bq/m³ through engineering controls where possible. Ontario's mines regulation (RRO 1990, Reg. 854) addresses radon at sections 288 to 293; those duties are not transcribed here until the regulation text is read. | Ontario guidance, Radon in the workplace (applying the Canadian NORM Guidelines under the general duty clause) | Guidance | no data |
| Building code | Canada (federal or national) | The radon rough-in with a capped stub was added to the National Building Code in 2010 and adopted by several provinces and territories. A rough-in is not a working mitigation system; code compliance does not guarantee a level below 200 Bq/m³, and only testing shows the actual level. Health Canada says current best practice calls for more complete systems. | National Building Code of Canada, radon rough-in provisions (2010 edition onward) | In force | 2010-01-01 |
| Professional certification | Canada (federal or national) | Canada has no licensing system for radon testers or mitigators. Health Canada recommends professionals certified through C-NRPP, but certification is voluntary, and no province has regulated radon professionals even though provinces have that power. | No licensing statute; C-NRPP certification is voluntary | No rule | no data |
| Real estate disclosure | Canada (federal or national) | High radon is treated as a latent defect by many real estate councils and associations; licensees must disclose known latent defects and help clients negotiate who pays for testing and mitigation. No province requires a radon test before a resale closes. Property disclosure statements in Nova Scotia, New Brunswick, Quebec and British Columbia include a radon line. | Latent defect disclosure duties under provincial real estate regulation | Guidance | no data |
| Guideline | Canada (federal or national) | The 200 Bq/m³ guideline is a federal health guideline, not a general legal limit for homes. For an ordinary existing home, no Canadian law requires testing, and none requires mitigation when a result exceeds 200 Bq/m³. | Government of Canada radon guideline, 200 Bq/m³ | Guidance | no data |
| Municipal liability | Canada (federal or national) | Once a local government decides to inspect building plans and construction, it owes a common law duty of care, and courts have found cities liable where inspectors failed to find design and construction flaws. A municipality is not automatically liable whenever a building tests high; the limits vary by province. | Rothfield v. Manolakos [1989] 2 SCR 1259; Just v. British Columbia, 1989 CanLII 16 (SCC); Ingles v. Tutkaluk Construction Ltd., 2000 SCC 12 | Tribunal or court decision | no data |
| Schools and child care | Canada (federal or national) | No Canada-wide law requires radon testing in schools or child care. Health Canada documents testing initiatives across provinces, but testing programs are not legal requirements. | No Canada-wide statute | No rule | no data |
| Technical standard | Canada (federal or national) | Health Canada identifies the 2019 CGSB standard as the recognized Canadian mitigation standard and recommends that building codes reference it. CARST describes three protection levels: Level 1, a rough-in for active soil depressurization; Level 2, Level 1 plus a full passive vertical radon stack; Level 3, Level 2 plus a fan. Most provinces require protection similar to Level 1. A standard is not law unless a code or regulation adopts it. | CGSB, Radon control options for new construction in low-rise residential buildings (2019) | Guidance | no data |
| Rental housing | Canada (federal or national) | Every province and territory has tenancy law requiring rental housing to be habitable and in good repair. There is no radon-specific statute requiring rental homes to be tested; tenants rely on general repair and habitability rules. Tenants are separately protected by occupiers' liability law. | Provincial and territorial tenancy legislation (habitability and repair duties) | Guidance | no data |
| Workers' compensation | Canada (federal or national) | Alberta, Nova Scotia, and Newfoundland and Labrador list diseases caused by ionizing radiation. British Columbia is the province Health Canada identifies as listing radon and lung cancer by name. | Provincial workers' compensation disease schedules | Guidance | no data |
| Workplace | Canada (federal or national) | The federal workplace regulation bars exposure of employees, other than nuclear energy workers, to a yearly average above 800 Bq/m³. SOR/2026-10, registered 30 January 2026 and published in the Canada Gazette on 11 February 2026, replaces the limit with 200 Bq/m³ and makes it the employer's duty, in force on 30 January 2027. Part II of the Canada Labour Code covers about 1.3 million employees, roughly 8% of the workforce. | Canada Occupational Health and Safety Regulations, SOR/86-304, s. 10.26(4); amended by SOR/2026-10 | In force | 2027-01-30 |
The radon rules dataset; each row cites its primary source and the date checked.
Provenance
- Source
- 2024 Cross-Canada Radon Survey, Version 1.1 (CCSR.24.1.1); C-NRPP Find a Professional directory, pulled 2026-10-18.
- Method
- Survey figures are reproduced as printed, by reporting unit. Provider counts are businesses whose registry address is in this place with at least one unexpired credential; nothing is typed by hand.
- Date checked
- 2026-10-18
- Next review
- 2026-11-18
Sources
- 1. Cross-Canada Survey of Radon Exposure in the Residential Buildings of Urban and Rural Communities, 2024 Report, Version 1.1 (CCSR.24.1.1), released October 2024, ISSN 2818-8195. Cross-Canada Survey of Radon working group.
- 2. C-NRPP, Find a Professional directory: every province and territory searched for each of the six service types, de-duplicated by the registry's person id. Pulled on 2026-10-18.