135 homes across Ottawa were long-term tested for radon in the two federal surveys. Every one is a dot on this map, coloured by what it read, with the number of tested homes printed beside every district figure.
Every dot is one tested house. Zoom in for street names. Shaded districts had no home tested in either survey. This page covers postal districts K1, K2 and K4. The whole province is on the Ontario map.
under 100100 to 147148 to 199200 and aboveno homes tested
135 measurements shown. Dot positions inside a district are illustrative, not addresses. The survey records which district a home was in, never where it stood. Tap any dot for its reading, or any district for its count and median. Rural districts here cover thousands of square kilometres, so a dot in one says very little about any particular corner of it.
Ottawa sits 24th of the 33 places mapped with a hundred or more tested homes, at 8.1% at or above the action level, between Halifax at 35.2% and Toronto and the GTA at 2.2%. All on the same two surveys and the same method. The spread between places is real, and the spread between houses on one street is bigger still.
Canada acts at 200 Bq/m³. The United States EPA acts at about 148. The World Health Organization sets a reference level of 100. Applied to the same 135 homes:
Same houses, same measurements. Why the three numbers differ, and which one to use.
| District | Land km² | Homes tested | Median | Highest | At or over 200 |
|---|---|---|---|---|---|
| K2L | 6 | 3 | 188 | 285 | 1 |
| K1V | 35 | 7 | 133 | 342 | 2 |
| K2W | 65 | 2 | 124 | 165 | 0 |
| K1Z | 7 | 3 | 109 | 157 | 0 |
| K2E | 11 | 5 | 106 | 167 | 0 |
| K4K | 54 | 13 | 105 | 303 | 2 |
| K4A | 33 | 5 | 102 | 168 | 0 |
| K2K | 15 | 6 | 101 | 251 | 1 |
| K2A | 5 | 3 | 86 | 108 | 0 |
| K1B | 11 | 5 | 85 | 155 | 0 |
| K2T | 12 | 3 | 84 | 124 | 0 |
| K1Y | 6 | 3 | 83 | 199 | 0 |
| K1J | 13 | 4 | 78 | 460 | 1 |
| K1K | 13 | 3 | 78 | 143 | 0 |
| K2M | 9 | 7 | 77 | 224 | 1 |
| K2J | 32 | 8 | 75 | 188 | 0 |
| K1C | 18 | 1 | 69 | 69 | 0 |
| K2H | 17 | 3 | 67 | 170 | 0 |
| K2S | 132 | 6 | 66 | 138 | 0 |
| K2G | 28 | 10 | 62 | 477 | 3 |
| K2P | 1 | 2 | 62 | 87 | 0 |
| K2B | 8 | 5 | 60 | 103 | 0 |
| K1M | 3 | 2 | 57 | 73 | 0 |
| K1G | 36 | 7 | 51 | 105 | 0 |
| K1N | 4 | 5 | 47 | 91 | 0 |
| K4R | 88 | 4 | 46 | 145 | 0 |
| K1S | 6 | 4 | 44 | 81 | 0 |
| K1H | 7 | 3 | 41 | 153 | 0 |
| K1T | 46 | 2 | 41 | 45 | 0 |
| K1L | 3 | 1 | 33 | 33 | 0 |
2 districts have ten or more tested homes, which is where these figures start to mean something. The districts with no measurement at all are K1A, K1E, K1P, K1R, K1W, K1X, K2C, K2R, K2V, K4B, K4C, K4M, K4P.
Nothing on this page describes your house. Radon varies enormously between homes on the same street, because it depends on how each building sits on and draws air from the ground beneath it. The highest reading here is 477 Bq/m³ and it sits in a district whose median is far below it. A long-term test in your own home is the only measurement that tells you anything about your home.
Also: every C-NRPP certified radon company here, the other city and province maps, and what radon actually is.
Sources and method. Radon measurements: Health Canada, Radon and Thoron Data From Canadian Homes pooled with the Cross-Canada Survey of Radon Concentrations in Homes 2009-2011, both under the Open Government Licence – Canada. Boundaries: Statistics Canada 2021 cartographic forward sortation area file, same licence. Percentages are calculated from the individual measurements shown, not quoted from a summary. Land areas are from the Statistics Canada boundary file.