Radon in the Workplace in Quebec: The Employer's Obligations (CNESST)

Quick answer: Yes — but the details matter. In Quebec, the provincial occupational health and safety regime — the Act respecting occupational health and safety (LSST), enforced by the CNESST — sets no numerical radon limit at all. Instead, the employer is bound by a general duty: to take the measures necessary to protect the health of its workers, using Health Canada's 200 Bq/m³ guideline as the reference point. Running in parallel, a second regime applies to a minority of Quebec employers: businesses under federal jurisdiction (banks, telecommunications, interprovincial transport, and so on), which are now subject to a binding 200 Bq/m³ limit introduced by regulation SOR/2026-10, coming into force on 30 January 2027.

This article untangles the two regimes, with official sources, and explains in concrete terms how a Quebec employer should approach radon: where to test, who is certified to do it, and what to do above 200 Bq/m³. It is not a substitute for legal advice — for your specific situation, confirm with the CNESST or a qualified professional.

Does the CNESST set a radon limit in the workplace?

No — there is no specific number. This is the point most people get wrong, so let's say it plainly: neither the LSST nor the Regulation respecting occupational health and safety (RSST, CQLR c. S-2.1, r. 13) sets a maximum radon concentration in Bq/m³ for provincial workplaces. There is no provision in Quebec's regulations that says "radon must not exceed X Bq/m³ at work."

That does not mean the employer is off the hook — quite the opposite. In Quebec, radon is governed through the employer's general duty (see the next section), and the reference threshold used in practice is the federal Health Canada guideline: 200 becquerels per cubic metre (200 Bq/m³), in effect since 2007. According to Health Canada, that guideline applies explicitly to homes and to public buildings and workplaces occupied more than 4 hours per day — schools, hospitals, seniors' residences, and "other indoor workplaces."

Two important clarifications to keep things straight:

• 200 Bq/m³ is not a "risk-free threshold." According to Health Canada, there is no radon level free of risk; 200 Bq/m³ is the level at which action is recommended. The higher the concentration, the sooner you should act.
• In Quebec, 200 Bq/m³ is a reference, not a provincial legal limit. The distinction is real: at the federal level, as we'll see, 200 Bq/m³ becomes a genuine binding limit; at the provincial level, it is the recognized benchmark for judging whether the employer has met its general duty.

Bottom line: You can search the RSST in vain for a "radon number" — there isn't one. But the absence of a regulatory figure does not exempt the employer from acting — it forces the employer to fall back on the general duty to protect health, with 200 Bq/m³ as the benchmark.

The employer's general duty: what the LSST says

In Quebec, the cornerstone is section 51 of the LSST. Its opening paragraph sets out a broad and demanding obligation:

"The employer must take the necessary measures to protect the health and ensure the safety and physical and mental well-being of the worker."

This is an outcome-oriented duty aimed at prevention: the employer must act as a reasonable and prudent person would to protect its workers, even in the absence of a regulation putting a number on a given hazard. Since the modernization of the LSST that came into force on 6 October 2021, section 51 lists 16 specific obligations that flesh out this general duty. Several apply directly to radon:

• Paragraph 4° — "control the keeping of the workplaces, provide sanitary facilities, drinking water, adequate lighting, ventilation and heating." Radon is a problem of indoor air and of ventilation in low-lying, poorly aired spaces; air quality therefore falls squarely under this obligation.
• Paragraph 5° — "use methods and techniques intended to identify, control and eliminate risks to the health and safety of the worker." Identifying a risk means, among other things, measuring it when it is invisible — which is precisely the case with radon.
• Paragraph 8° — "ensure that the emission of a contaminant or the use of a hazardous material does not impair the health or jeopardize the safety of any person at a workplace." Radon is a radioactive gas, classified a Group 1 human carcinogen by the International Agency for Research on Cancer.

In other words, even without a named radon threshold in Quebec's regulations, an employer who knows — or should reasonably know — that its building sits in a high radon potential region and does nothing could be in breach of its general duty. Section 51 is, in fact, the provision most frequently cited by CNESST inspectors during their interventions.

On top of this comes the prevention "taking-charge" framework introduced by the 2021 reform: every establishment must now put prevention mechanisms in place (a program or an action plan depending on size and risk level), designate people responsible for health and safety, and identify the risks specific to its premises. For a building located in a radon-risk zone, a rigorous identification exercise logically leads to measuring radon.

Bottom line: Quebec has no specific "radon rule" for the workplace, but it has something more demanding in some respects: a general duty to protect health that covers radon by default. The question is not "does the law require me to measure a number?" but "have I taken reasonable measures to protect my workers from a known carcinogen?"

Federal vs. provincial workplaces: why the distinction is crucial

Not every employer in Quebec is governed by the same occupational health and safety regime. This is arguably the most important — and most misunderstood — point in the whole file.

The vast majority of Quebec employers fall under the provincial regime (LSST / RSST, enforced by the CNESST). This is the case for almost all stores, factories, offices, daycares, restaurants, professional offices, municipalities, and so on.

A minority of employers fall instead under federal jurisdiction, and are governed by Part II of the Canada Labour Code and its regulations — not by the LSST. According to the Government of Canada, federally regulated sectors include, among others:

• banks;
• telecommunications and broadcasting (telephone, internet, cable distribution, radio, television);
• interprovincial and international transportation: air (including airports), rail, road (interprovincial trucking), and marine;
• port services and shipping;
• interprovincial pipelines and grain handling (grain elevators);
• atomic energy and uranium;
• most federal Crown corporations.

For these federal employers, it is regulation SOR/2026-10 (see below) that applies — with a genuine numerical limit. For everyone else, it is the LSST general duty.

Comparison table: provincial vs. federal regime

The federal regime: SOR/2026-10 and the 200 Bq/m³ limit

On 30 January 2026, the Government of Canada registered regulation SOR/2026-10 (Regulations Amending Certain Regulations Made Under the Canada Labour Code), published in Part II of the Canada Gazette on 11 February 2026. This regulation updates the requirements for hazardous substances in federally regulated workplaces, including radon.

The key change: the former limit of 800 Bq/m³ is replaced by a limit of 200 Bq/m³. The text of the new subsection 10.26(4) of the COHSR is unambiguous:

"The employer must ensure that no employee — other than a nuclear energy worker, as defined in section 2 of the Nuclear Safety and Control Act — is exposed, on average over the course of a year, to a concentration of radon exceeding 200 Bq/m³."

According to the regulation's Regulatory Impact Analysis Statement, the former 800 Bq/m³ limit was no longer consistent with the Health Canada guideline (lowered from 800 to 200 Bq/m³ back in 2007), and the new radon testing and mitigation requirements will affect all workplaces covered by the Code where radon is present. The regulation comes into force on the first anniversary of its registration, that is, on 30 January 2027.

So if you are a federal employer, you go from an informal benchmark to a regulatory obligation: there is good reason to measure now, ahead of the deadline.

Bottom line: A Quebec employer's first question is not "how many Bq/m³?" but "do I fall under provincial or federal jurisdiction?" Provincial: general duty + 200 as a reference. Federal: 200 Bq/m³ as a binding limit starting in 2027. In both cases, the same concrete action follows — test.

How should an employer test for radon in the workplace?

Measuring radon in an occupied building is not quite the same as in a home. Health Canada publishes a dedicated guide — the Guide for Radon Measurements in Public Buildings (schools, hospitals, care facilities, workplaces) — that sets out the protocol to follow. The main principles:

1. Run a long-term test. Radon varies enormously from day to day and from season to season. Health Canada recommends a measurement of at least 3 months (91 days or more), ideally during the heating season (fall–winter), when windows stay closed. Short-term tests are not enough to decide whether to act.
2. Measure in normally occupied areas, on the lowest occupied level. Place detectors where people spend more than 4 hours per day: basement or ground-floor offices, workshops, classrooms, permanent workstations. Avoid rarely occupied rooms (storage, boiler room, crawl space), and account for the size of the building — a large building requires several detectors distributed according to the protocol.
3. Use proper detectors and a certified laboratory. The recognized standard in Canada is the long-term alpha track detector, analyzed by a laboratory certified under the Canadian National Radon Proficiency Program (C-NRPP).
4. Document everything. Locations, deployment and retrieval dates, duration, results in Bq/m³. This documentation is valuable for demonstrating the employer's due diligence — and essential for a federal employer subject to record-keeping requirements.

Who can take the measurement? An employer can call on a C-NRPP-certified measurement professional (recommended for large buildings or complex situations), or deploy long-term alpha track detectors itself by following the protocol rigorously, then have them analyzed by a certified laboratory. To find a certified professional, consult the C-NRPP directory.

Helpful link: Want to know whether your building sits in a high radon potential zone? See our radon map of Quebec and the at-risk regions. A location in a risk zone substantially strengthens the relevance — and the duty of diligence — to measure.

What to do if the result exceeds 200 Bq/m³

Exceeding the guideline is neither an immediate emergency nor a hopeless situation: radon acts over the long term, and reduction techniques are proven and effective. The steps depend on your regime, but the underlying logic is the same.

• Act according to the measured level. The higher the concentration, the sooner you should act. For an exceedance, Health Canada recommends bringing the level down as low as reasonably achievable, generally within one year (and faster still for very high concentrations).
• For a federal employer (SOR/2026-10): compliance with the 200 Bq/m³ limit becomes an obligation. An exceedance calls for corrective measures, and the situation must be managed in accordance with the COHSR (mitigation, records, air sampling).
• For a provincial employer (LSST): exceeding the 200 Bq/m³ reference is a clear signal that you must act under the general duty. Doing nothing in the face of a high result exposes you to a breach of section 51.

The most common technical solution is active soil depressurization: a system that captures radon beneath the slab and vents it outside the building, installed by a C-NRPP-certified mitigation professional. Other approaches (improving ventilation, sealing entry routes) can complement it or, in some cases, suffice. After the work, you measure again to confirm the fix was effective.

For detailed next steps, see our guide What to do if your radon level is above 200 Bq/m³, and for budget orders of magnitude, our article on the cost of radon mitigation in Canada.

Radon in schools, daycares, and public buildings

Schools, childcare services, and other public buildings deserve a special mention, because they are both workplaces (for staff) and places where sensitive populations spend time (children, the sick, the elderly).

Quebec has, in fact, already acted on the schools front: starting in 2011, the Ministère de l'Éducation carried out a large-scale radon testing operation covering all primary and secondary schools in the province, with corrective work wherever the 200 Bq/m³ guideline was exceeded. The CPE (early childhood centres) and daycare network, by contrast, has only been the subject of pilot projects — the picture there is far less uniform. We cover this subject in detail in our sibling article, Radon in Quebec schools and daycares (CPEs).

For these buildings, the measurement protocol is the one in Health Canada's Guide for Radon Measurements in Public Buildings — the same long-term, alpha track, C-NRPP-certified approach described above. And the same rule applies on the responsibility side: whether you fall under the CNESST (virtually all schools and childcare facilities in Quebec) or not, the duty to protect the health of occupants calls for measuring rather than guessing.

Testing your workplace for radon: where to start

Whether you fall under the provincial or federal regime, the first step is the same and affordable: measure. The recognized method is a long-term alpha track test, analyzed by a C-NRPP-certified laboratory — exactly what RadonTest.ca offers.

The RadonTest.ca radon test kit is built on a 91-day-or-longer alpha track detector, analyzed by a C-NRPP-certified laboratory, with prepaid return shipping included and an analyzed-in-Canada option. It's the same measurement technology used in Quebec's schools and public buildings — applied to your workplace. For multiple workstations or a large building, deploy as many detectors as the protocol requires, or call on a C-NRPP-certified measurement professional.

Order a radon test kit → — all-in, analyzed in Canada, prepaid return shipping.

For the big-picture view of radon in the province — risks, regions, regulations — see our pillar guide Radon in Quebec.

Frequently Asked Questions

Does the CNESST impose a radon limit in Quebec workplaces? No. Neither the Act respecting occupational health and safety (LSST) nor the Regulation respecting occupational health and safety (RSST) sets a maximum radon concentration in Bq/m³. Radon is governed by the employer's general duty (section 51 of the LSST) to protect the health of its workers, with Health Canada's 200 Bq/m³ guideline as the reference value.

Is a Quebec employer required to test for radon? At the provincial level, there is no explicit, numerical obligation to measure radon. But section 51 of the LSST requires employers to identify, control, and eliminate risks to workers' health. For an invisible carcinogen like radon, especially in a building located in a high-potential zone, measuring is the reasonable way to meet that obligation. Federally regulated employers, for their part, are subject to a binding 200 Bq/m³ limit starting in 2027 (SOR/2026-10).

What is the difference between a provincially and a federally regulated employer for radon? The majority of Quebec employers fall under the provincial regime (LSST/RSST, CNESST): general duty, 200 Bq/m³ as a reference. A minority — banks, telecommunications, broadcasting, interprovincial transport, ports, pipelines, grain, uranium, most Crown corporations — fall under the Canada Labour Code, where SOR/2026-10 sets a binding limit of 200 Bq/m³ as an annual average, in force on 30 January 2027.

What does regulation SOR/2026-10 change for radon? For federally regulated workplaces, it lowers the radon exposure limit from 800 Bq/m³ to 200 Bq/m³ as an annual average, aligning it with the Health Canada guideline, and adds testing and mitigation requirements. Published in Part II of the Canada Gazette on 11 February 2026, it comes into force on the first anniversary of its registration, that is, 30 January 2027.

Is the 200 Bq/m³ threshold an acceptable level? No. According to Health Canada, there is no radon level free of risk. 200 Bq/m³ is the level at which action is recommended — and the higher the concentration, the sooner you should act. Provincially, it is a reference; federally (SOR/2026-10), it is a binding limit.

How do you test for radon in a workplace? With a long-term test (91 days or more, ideally during the heating season), using alpha track detectors placed in areas occupied more than 4 hours per day, on the lowest occupied level, and analyzed by a C-NRPP-certified laboratory. Health Canada publishes a specific guide for measurements in public buildings and workplaces. You document the locations, dates, and results.

Who can measure radon in a commercial building in Quebec? A professional certified in measurement by the Canadian National Radon Proficiency Program (C-NRPP), recommended for large buildings. An employer can also deploy long-term alpha track detectors itself by following Health Canada's protocol, then have them analyzed by a C-NRPP-certified laboratory.

What should I do if radon exceeds 200 Bq/m³ at work? Take corrective measures, prioritizing according to the level (the higher it is, the more urgent), generally within one year. The most common technique is active soil depressurization, installed by a C-NRPP-certified professional, followed by a new measurement to confirm it worked. For a federal employer, complying with the 200 Bq/m³ limit is a regulatory obligation.

Sources

• Act respecting occupational health and safety (CQLR c. S-2.1), section 51 — LégisQuébec — The employer's general duty to protect the health and safety of the worker and the list of 16 specific obligations (text in force since 6 October 2021).
• Regulation respecting occupational health and safety (CQLR c. S-2.1, r. 13) — LégisQuébec — Application regulation under the LSST; sets no specific radon exposure limit.
• Federally regulated business — CNESST — Distinction between provincially and federally regulated employers in Quebec.
• Federally regulated industries and workplaces — Government of Canada — Official list of federally regulated sectors (banks, telecommunications, interprovincial transport, etc.).
• SOR/2026-10 — Regulations Amending Certain Regulations Made Under the Canada Labour Code, Canada Gazette, Part II (11 February 2026) — New radon exposure limit of 200 Bq/m³ (subsection 10.26(4) of the COHSR), replacing the former 800 Bq/m³ threshold; in force on the first anniversary of registration.
• Canada Occupational Health and Safety Regulations (SOR/86-304) — Justice Laws — Federal regulations applying Part II of the Canada Labour Code.
• Guidelines for Canadian Radon — Health Canada — The 200 Bq/m³ guideline applicable to homes, public buildings, and workplaces occupied more than 4 hours per day; no risk-free level; remediation recommended within one year.
• Guide for Radon Measurements in Public Buildings — Health Canada — Protocol for measuring radon in schools, hospitals, care facilities, and workplaces.
• Radon in Buildings — Canadian Centre for Occupational Health and Safety (CCOHS) — OHS reference sheet: carcinogen classification, units of measurement, at-risk sectors, the 200 Bq/m³ guideline, and CNSC dose limits.
• Radon: What You Need to Know — Health Canada — Long-term test (91 days or more) certified by the C-NRPP; radon as the leading cause of lung cancer among non-smokers.
• Canadian National Radon Proficiency Program (C-NRPP) — Directory of professionals certified in radon measurement and mitigation.

This article is provided for informational purposes and does not constitute legal advice. To determine your specific radon obligations, confirm with the CNESST, the Labour Program (for federal employers), or a qualified professional.