In Canada, the new federal workplace radon limit of 200 Bq/m³ comes into force on January 30, 2027. That is the legal date. But the regulation contains no test-by date — and that absence confuses employers into thinking timing is flexible. It isn't. The limit is an annual average, the recognized way to establish an annual average is a long-term test of at least 91 days, and 91 days counted back from January 30, 2027 lands in early November 2026. The measurement calendar is set by arithmetic, not by the regulator.
TL;DR: January 30, 2027 is the legal date; fall 2026 is the measurement date. An employer who places long-term detectors by early November 2026 has a defensible annual-average measurement in hand the day the duty takes effect. An employer who waits until January 2027 cannot demonstrate their position until late spring — months into the compliance period. The regulation never says "test by November"; the math does.
What the duty actually requires
As amended by SOR/2026-10, the Canada Occupational Health and Safety Regulations state that "the employer must ensure" no employee (other than nuclear energy workers) "is exposed in any year to a concentration of radon that on average, over the year, is higher than 200 Bq/m³." Read the two operative parts together: the employer must ensure, and the measure is an annual average. You cannot ensure what you have not measured, and you cannot measure an annual average with an afternoon's spot reading. Radon levels swing by hour, day and season — highest in the heating months when buildings are sealed — which is exactly why Health Canada's measurement guidance for public buildings specifies long-term testing: a minimum of three months, during the heating season, in occupied rooms in contact with the ground. (Three months is commonly operationalized as 91 days; Health Canada's public-buildings guide states the requirement in months, its residential guide in days.)
The arithmetic
| Detectors placed | 91-day test completes | Position on January 30, 2027 |
|---|---|---|
| Early November 2026 | Late January – February 2027 | Measurement evidence in hand as the duty begins — and captured during the heating season, when levels are most representative of worst-case exposure |
| December 2026 | March 2027 | Testing demonstrably under way at in-force date; results follow within weeks |
| January 2027 | April – May 2027 | Three to four months into the duty period with no measurement evidence |
| Spring 2027 | Off-season | Outside the heating-season window Health Canada guidance prefers; another year's cycle in play |
One more reason the fall window matters: heating season is when radon concentrations are typically highest, so a heating-season measurement is the conservative, defensible basis for an annual-average position. A summer test that comes back low answers less than it appears to.
If your portfolio is too large to test in one season
The arithmetic above assumes one building, or a handful. Employers holding dozens or hundreds of untested buildings face a different problem: there is one heating season left, and long-term testing cannot be compressed.
Two points matter here. First, the deployment window is bounded at both ends. Detectors placed after the end of January push the 91-day period out of the heating season entirely, which undermines the representativeness of the result — so the practical deployment window runs from October 1 to the end of January, with early November the latest placement that still produces a result by the duty date.
Second, and less well known: there is no published extension scheme, but Part II of the Code is enforced along an escalating continuum in which, in the Labour Program's own words, escalation depends on "the seriousness of the violation and the co-operation of the workplace." Industry reporting indicates the Labour Program has acknowledged that testing a large untested portfolio by the in-force date may not be realistic, and that a documented phased approach can be a recognised path forward — available, not automatic. Three conditions are consistently described:
- It must be raised with and agreed by the Labour Program proactively, not asserted after the fact.
- It requires a documented plan, not an explanation.
- Employers who engage early are treated differently from employers who do nothing.
What a defensible phased programme contains:
- A risk-ranked building inventory — which buildings are tested first, and why. A defensible ranking weighs regional radon potential, occupancy pattern, building age and construction, and which floors occupants actually work on. How to build the ranking.
- A documented testing schedule with clear phase sequencing
- A framework showing how compliance will be reached
- Evidence of ongoing action and progress, not a plan on a shelf
- Formal engagement with the Labour Program on record
The distinguishing factor between an employer working toward compliance and one that is simply non-compliant is documented intent. Note also that the changes have been public since the Gazette I proposal in October 2023, so "we did not know" is not available as an explanation. Full detail, including where Assurances of Voluntary Compliance fit: phased radon compliance for large portfolios.
If that describes your situation, the action this fall is twofold — start testing your highest-risk buildings, and open the conversation with the Labour Program rather than waiting to be found.
The milestones between now and February 2027
| When | What |
|---|---|
| Now – September 2026 | Inventory your buildings and count the detectors each one needs. Workplace testing follows Health Canada's Guide for Radon Measurements in Public Buildings, not the residential protocol: every occupied room in ground contact gets a detector (an occupied room is one where someone spends 4+ hours a day), large rooms get one detector per 200 m², and quality control adds ~10% duplicates plus blanks. A house needs one detector; a workplace needs as many as its floor plan dictates — which is why the count is done now, not in November. |
| September – October 2026 | Plan detector placements and bring the plan to your policy or workplace health and safety committee. The same regulatory package that lowered the radon limit runs hazard procedures through these committees — involving them early is both the pattern the regulations expect and the fastest route to workforce buy-in. |
| Early November 2026 | Deploy long-term detectors. From placement onward the work is passive — the detectors simply sit for 91+ days. |
| February 2027 | Retrieve detectors, send for laboratory analysis, and build the record. The regulations specify what a test record must contain: the date, time and location of the test; the substance tested for; the sampling and testing method; the result; and the name and occupation of the person who made the test. The lab supplies only the result — the rest is field information you must capture at placement and retrieval. Retention is 30 years for hazard investigation and air sampling records. |
| If a result exceeds 200 Bq/m³ | Health Canada recommends remedial action, sooner the higher the level, carried out by certified mitigation professionals (C-NRPP), followed by retesting to confirm the fix. All health guidance on radon belongs to Health Canada — canada.ca/radon is the authoritative source. (We test and report; we don't perform mitigation.) |
| Ongoing | The duty is annual and continuous, not one-and-done: results feed your hazard records, mitigated sites get verified, and Health Canada guidance recommends periodic retesting. |
What this is not
To be precise, because precision matters here: there is no statutory requirement to test by November 2026, and no penalty attaches to the act of not-yet-testing this fall. What exists is an employer duty in force January 30, 2027, an annual-average metric, and a 91-day recognized measurement method. Fall 2026 is simply the last window in which those three facts can be reconciled before the duty begins. Employers who understand the arithmetic early get an unhurried, committee-endorsed, heating-season measurement; employers who discover the rule in January get the same obligation with none of the runway.
For workers and health and safety committees: radon at work — a guide for workers and committees.
Common questions
Is there a legal deadline to test for radon?
No. The regulation contains no test-by date. It contains an employer duty in force 30 January 2027, defined as an annual average — and the recognised measurement takes at least three months of heating season.
When should detectors be placed?
The usable deployment window runs roughly 1 October to the end of January. Early November 2026 is the latest placement that produces a result by the in-force date.
What if we cannot test every building this season?
A documented phased approach, raised with and agreed by the Labour Program, can be a recognised path forward. It is not automatic. See phased compliance for large portfolios.
Why does the heating season matter?
Stack effect is strongest when a building is heated and closed, so heating-season measurement is the conservative and representative basis for an annual average.
Read next
Commercial radon testing in Canada — detector counts, delivery models and cost ranges. SOR/2026-10 explained — the full rule in plain language. Is my workplace federally regulated? — the coverage question, including the confusing cases. The workplace radon FAQ — 22 questions employers and committees ask.
RadonTest.ca provides testing logistics and laboratory submission. We do not perform radon mitigation and we do not interpret health risk — Health Canada is the health authority on radon in Canada. This page describes publicly available regulatory information and is not legal advice.
Sources
Canada Gazette, Part II, Vol. 160, No. 3 (SOR/2026-10), including s. 77(1) coming-into-force provision and the Regulatory Impact Analysis Statement; Employment and Social Development Canada, Introducing amendments to regulations under Part II of the Canada Labour Code; Canada Occupational Health and Safety Regulations, ss. 10.3 and 10.26(4) as amended; Health Canada, Guide for Radon Measurements in Public Buildings (Workplaces, Schools, Day Cares, Hospitals, Care Facilities, Correctional Centres), H129-120/2022E; Health Canada, Canadian radon guideline.