Montreal Radon Map: Every Home Health Canada Tested, and What It Read

115 homes across Montreal 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.

The Map

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 H. The whole province is on the Quebec map.

under 100100 to 147148 to 199200 and aboveno homes tested

115 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.

Built from Health Canada's published measurements under the Open Government Licence. We do not sell radon testing or mitigation.

What the Numbers Say

16%

of tested Montreal homes at or above Canada's 200 Bq/m³ action level

median reading, Bq/m³

1,607

highest single reading, in H7M

Montreal sits 14th of the 33 places mapped with a hundred or more tested homes, at 15.7% 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.

The Number Changes Depending on Whose Limit You Use

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 115 homes:

16%

at or above Canada's 200

21%

at or above the US EPA's 148

36%

at or above the WHO's 100

Same houses, same measurements. Why the three numbers differ, and which one to use.

By Postal District, with the Sample Sizes Shown

Read the count column before the median column. A district resting on four houses is a hint, not a verdict, and those rows are greyed. The land area column matters too: a district covering ten thousand square kilometres is an average across a region, not a neighbourhood.

District	Land km²	Homes tested	Median	Highest	At or over 200
H1E	11	2	421	715	1
H1G	8	1	352	352	1
H7A	18	6	214	281	4
H1C	11	4	163	204	1
H9W	11	2	154	219	1
H1W	3	1	139	139	0
H7M	11	4	135	1607	2
H7P	16	8	130	297	1
H9C	9	2	127	238	1
H8Z	4	3	120	278	1
H7L	16	10	109	194	0
H9J	11	2	98	130	0
H9A	5	2	94	152	0
H1S	5	1	76	76	0
H7T	12	4	76	241	1
H1T	4	1	64	64	0
H7E	18	6	62	202	1
H1L	8	3	61	73	0
H9S	9	2	60	89	0
H7H	6	9	58	131	0
H7R	18	6	55	217	1
H7K	12	8	54	90	0
H1V	5	2	50	74	0
H7G	6	7	40	72	0
H7N	8	5	33	93	0
H3E	4	1	30	30	0
H7W	10	3	29	558	1
H7X	13	4	27	301	1
H8P	4	3	24	36	0
H1M	5	2	22	30	0
H4L	6	1	22	22	0

1 districts have ten or more tested homes, which is where these figures start to mean something. 86 districts have no measurement at all and are shaded on the map.

What Actually Settles It

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 1,607 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.