Health Canada long-term tested 99 homes across the Calgary area. One in seven came back above Canada's action level. Nearly one in three would be above the American one. More than half were above what the World Health Organization recommends.
15 of 99 homes. The highest single reading was 841 Bq/m³, more than four times the level at which Health Canada says you should act.
Radon is measured in becquerels per cubic metre. What counts as "too much" is a policy decision, and different authorities have drawn the line in different places. Applied to the same 99 Calgary homes:
Same houses. Same measurements. The proportion of Calgary homes considered to have a radon problem moves from one in seven to nearly three in five, purely on which country's threshold you apply.
The World Health Organization's handbook on indoor radon sets a reference level of 100 Bq/m³, and says that where national conditions make that unachievable it should still not exceed 300. Canada's guideline of 200 sits between those two figures. The United States Environmental Protection Agency acts at 4 picocuries per litre, which converts to about 148 Bq/m³, and suggests homeowners consider acting between 2 and 4 pCi/L, roughly 74 to 148.
None of these are safety guarantees. Every authority above states there is no known threshold below which radon exposure carries no risk. They are action levels, which is a different thing: the point at which fixing the problem is considered clearly worthwhile.
Every dot is one house that was tested, coloured by its reading. Zoom in for street names and community names. Shaded postal districts had no homes in this survey.
104 measurements are shown, pooled from Health Canada's two published surveys; a further nine were recorded without a postal area and cannot be placed. Dot positions within a postal district are illustrative, not addresses. The survey records which district a home was in, never where it stood, so each dot sits inside the correct district and nowhere more precise than that. Tap any dot for its reading, or any district for its count and median.
Calgary is not the worst place in Canada for radon. It is not close to the worst. Regina and Winnipeg are in a different category entirely.
| Metro area | homes tested | median Bq/m³ | ≥100 | ≥148 | ≥200 |
|---|---|---|---|---|---|
| Regina | 96 | 216 | 86% | 72% | 56% |
| Winnipeg | 99 | 194 | 80% | 62% | 47% |
| Halifax | 96 | 100 | 50% | 36% | 31% |
| Thunder Bay | 92 | 110 | 54% | 41% | 30% |
| Kingston | 95 | 128 | 62% | 43% | 26% |
| Sherbrooke | 104 | 90 | 44% | 33% | 24% |
| Windsor | 92 | 120 | 61% | 35% | 24% |
| Saskatoon | 104 | 140 | 72% | 47% | 21% |
| Guelph | 101 | 73 | 34% | 26% | 20% |
| Québec | 94 | 65 | 34% | 23% | 17% |
| Saint John | 107 | 74 | 37% | 26% | 17% |
| Greater Sudbury | 94 | 99 | 50% | 28% | 16% |
| Calgary | 99 | 112 | 58% | 31% | 15% |
| Kelowna | 106 | 88 | 45% | 31% | 15% |
| Montréal | 92 | 76 | 41% | 27% | 14% |
| Brantford | 85 | 72 | 38% | 24% | 14% |
| Saguenay | 90 | 59 | 30% | 20% | 13% |
| Ottawa - Gatineau | 105 | 84 | 41% | 23% | 10% |
| Edmonton | 96 | 108 | 54% | 25% | 8% |
| London | 80 | 65 | 24% | 11% | 8% |
| St. John's | 89 | 78 | 40% | 18% | 7% |
| Moncton | 90 | 62 | 21% | 10% | 7% |
| Peterborough | 100 | 84 | 43% | 17% | 6% |
| Hamilton | 87 | 62 | 26% | 14% | 6% |
| Barrie | 83 | 69 | 23% | 11% | 5% |
| Vancouver | 68 | 27 | 1% | 1% | 1% |
| Abbotsford | 84 | 48 | 10% | 1% | 1% |
| Oshawa | 92 | 46 | 16% | 7% | 1% |
| Kitchener | 101 | 57 | 15% | 3% | 1% |
| Victoria | 89 | 32 | 3% | 1% | 0% |
| St. Catharines - Niagara | 84 | 46 | 15% | 2% | 0% |
| Toronto | 86 | 48 | 17% | 3% | 0% |
| Trois-Rivières | 89 | 41 | 1% | 0% | 0% |
Calgary sits in the middle. Roughly one home in seven above Canada's line, against more than half of tested homes in Regina. Vancouver, Victoria and Toronto are close to untroubled.
That context is worth having, because the useful question is not whether your city is on a list. It is whether your house is above the line, and the only way to know that is to test the house.
The federal data records each measurement against a forward sortation area, the first three characters of the postal code. Here is every Calgary area with at least two tested homes.
| Postal area | homes tested | median Bq/m³ | highest reading |
|---|---|---|---|
| T3P | 3 | 309 | 453 |
| T2W | 4 | 245 | 344 |
| T3C | 3 | 211 | 252 |
| T3H | 4 | 196 | 841 |
| T3Z | 3 | 187 | 231 |
| T2V | 2 | 148 | 200 |
| T2J | 2 | 142 | 245 |
| T3E | 2 | 142 | 155 |
| T2H | 3 | 137 | 206 |
| T2X | 2 | 126 | 154 |
| T3J | 2 | 126 | 229 |
| T2A | 3 | 123 | 158 |
| T1Y | 4 | 118 | 125 |
| T3R | 2 | 114 | 156 |
| T2K | 2 | 109 | 129 |
| T2E | 4 | 108 | 116 |
| T2Z | 6 | 102 | 154 |
| T2B | 6 | 102 | 153 |
| T2L | 3 | 98 | 161 |
| T3M | 5 | 98 | 137 |
| T3K | 3 | 97 | 132 |
| T3G | 5 | 95 | 393 |
| T3B | 2 | 91 | 101 |
| T2C | 3 | 87 | 119 |
| T3A | 6 | 82 | 122 |
| T3L | 3 | 78 | 150 |
| T2T | 3 | 61 | 78 |
Everything above is Health Canada's own measurements, and they were taken between 2009 and 2011. A newer and much larger survey has since been published, and it does not agree with them. It is worse.
A further 24.2% live between 100 and 199 Bq/m³. The 2024 Cross-Canada Survey of Radon, a collaboration between the Evict Radon National Study at the University of Calgary, the BC Centre for Disease Control and Health Canada, drawing on tests taken between 2009 and 2024.
For Calgary specifically that survey reports roughly a one in six chance of a home being at or above the guideline, with a weighted average between about 80 and 110 Bq/m³. That is close to what the older data on this page shows, so Calgary itself has held reasonably steady.
The towns around Calgary are a different story. The same survey names High River, Okotoks and Strathmore among Canadian municipalities where between a quarter and a half of homes contain radon at or above 200 Bq/m³, alongside Whitehorse, Kelowna, Prince George, Nelson, Vernon, Penticton, Trail, Regina, Brandon, Winnipeg, Thunder Bay, Kingston, Sherbrooke, Bathurst and Halifax. Many of those places average above 130 Bq/m³.
So if you are in the towns south and east of the city, the older map above almost certainly understates your risk. And the national trend is the thing to take seriously: the share of Canadian homes above the guideline has roughly tripled between the two surveys, which is consistent with newer housing being built tighter and better sealed.
Source: Cross-Canada Survey of Radon working group, a collaboration between the Evict Radon National Study, BC Centre for Disease Control and Health Canada. Cross-Canada Survey of Radon Exposure in the Residential Buildings of Urban and Rural Communities. 2024, Version 1. Available at crosscanadaradon.ca.
A long-term test, at least three months and ideally over the heating season, in the lowest lived-in level of the house. Short-term tests bounce around with weather, ventilation and how often the doors have been open, which is why every guideline above is written in terms of long-term averages.
If a reading comes back above the line, the fix is well understood. Sub-slab depressurization, a pipe and a fan that vents soil gas above the roofline before it enters the house, routinely cuts levels by most of the way and works in existing homes.
Radon turns up most often at the worst possible moment, partway through a transaction with a conditions date approaching. Two things are worth knowing. A long-term test takes longer than most condition periods allow, so what gets used in a live deal is usually a short-term test with its limitations understood. And mitigation is a days-long job, not a months-long one, which means a radon result does not have to end a deal.
Source and method. All measurements are from Radon and Thoron Data From Canadian Homes, published by Health Canada on the federal open data portal at open.canada.ca. The file contains 3,190 long-term measurements across 33 census metropolitan areas, recorded by forward sortation area. The Calgary figures above are the 99 measurements recorded against the Calgary census metropolitan area. Medians are used rather than means because a single very high reading distorts an average in a small sample. Metro areas with fewer than 60 tested homes are omitted from the national table.
Contains information licensed under the Open Government Licence - Canada.
Reference levels quoted: World Health Organization, Handbook on Indoor Radon: A Public Health Perspective (100 Bq/m³, not to exceed 300); United States Environmental Protection Agency action level of 4 pCi/L, converting at 1 pCi/L = 37 Bq/m³; Health Canada guideline of 200 Bq/m³.
This page reports published measurements. It is not a health assessment of any individual property, and no reading here describes any specific address.
People ask about Airdrie, Okotoks, Cochrane, Chestermere and Strathmore constantly, so here is the honest position on all of them.
Airdrie, Okotoks, Cochrane and Chestermere have no published radon measurements at all. Not a low reading, not a high one. Nobody in either federal survey tested a house there. Anyone who tells you those towns are safe, or that they are a hotspot, is telling you something the data does not contain.
Where measurements do exist around Calgary, 127 of them, they look like this:
| Area | Homes tested | Median | Highest | At or over 200 |
|---|---|---|---|---|
| Canmore | 6 | 130 | 257 | 2 |
| Didsbury, Olds and Carstairs | 18 | 124 | 570 | 5 |
| Strathmore | 6 | 94 | 175 | 0 |
| Southern Alberta, rural | 55 | 91 | 719 | 4 |
| High River area | 2 | 78 | 113 | 0 |
| Bragg Creek, Turner Valley and Kananaskis | 37 | 69 | 367 | 3 |
| Banff | 3 | 22 | 24 | 0 |
Two things stand out, and the second one is uncomfortable. Canmore and the Didsbury and Olds area read higher than Calgary itself. And the rural districts hold the extremes: the highest single readings in this whole dataset, 719 and 570 Bq/m³, are both outside the city.
The practical version for anyone buying or selling outside the city: the countryside is not safer than Calgary, it is less measured. Those are very different things.
Alberta has required a radon rough-in in new homes since 1 November 2015, which splits the housing stock in two: on a newer house mitigation is a connection, on an older one it is a full installation. Same reading, different job, and the build year is on the listing. What the November 2015 line means for a sale.
Also: every C-NRPP certified radon company in the Calgary area, sorted by what they actually do, and what counts as a safe radon level.