What Do Health Canada’s Radon Guidelines Actually Mean?

If you’ve had your home tested for radon, seen it mentioned in a real estate listing, or come across it while researching indoor air quality, you’ve probably seen the number 200 Bq/m³ somewhere. It’s referenced constantly, but rarely explained. Where does it come from? Who decided on it? And what does it actually mean for your home? Here’s a clear, factual breakdown so you can interpret your own results with confidence.

What Is Radon Measured In?

Radon concentration is measured in becquerels per cubic metre (Bq/m³). A becquerel represents one radioactive decay event per second, so this unit reflects how much radioactive activity — and therefore how much radon gas — is present in a given volume of air. It’s the standard measurement used across Canada for indoor radon testing, so it’s the number you’ll see on any Canadian test report.

What Is Health Canada’s Radon Guideline?

Health Canada recommends taking corrective action when the long-term average radon concentration in the normal living area of a home exceeds 200 Bq/m³. This isn’t based on a single reading — it refers to the average level measured over an extended period, ideally at least three months.

The guideline was developed by Health Canada in collaboration with the Federal Provincial Territorial Radiation Protection Committee, based on a scientific risk assessment combined with broad public consultation. It’s periodically reviewed as new research becomes available. You can read Health Canada’s full guideline directly on the Government of Canada’s radon guideline page.

Is the Guideline a “Safe” Cutoff?

It’s natural to read 200 Bq/m³ as a line between “safe” and “dangerous,” but that’s not quite how it works. Health Canada is clear that while health risk below the guideline is small, there is no radon level that is considered completely risk-free.

In practical terms, this means:

• A result below 200 Bq/m³ doesn’t require action, but it doesn’t guarantee zero risk either
• A result just above the guideline isn’t cause for alarm — it simply indicates that corrective action is recommended
• Homeowners who want to reduce risk further can choose to do so even below the guideline

The guideline exists to give homeowners a practical, evidence-based benchmark for decision-making — not a strict pass-or-fail line.

How Does Canada’s Guideline Compare to Other Countries?

Radon guidelines differ slightly around the world, which can be confusing when comparing sources.

• The World Health Organization (WHO) recommends a reference level of 100 Bq/m³, with a maximum of 300 Bq/m³ in cases where 100 isn’t achievable due to local conditions.
• The U.S. EPA uses an action level of 4 picocuries per litre (pCi/L), which converts to approximately 148 Bq/m³.
• Canada’s guideline of 200 Bq/m³ falls within the WHO’s recommended range.

Health Canada has reviewed the WHO’s recommendation and opted to keep the Canadian guideline at 200 Bq/m³, noting it falls within the WHO’s acceptable range of 100–300 Bq/m³. A different number doesn’t mean a different scientific conclusion — it reflects each jurisdiction weighing feasibility, housing stock, and public health resources differently. Across all three guidelines, the underlying message is the same: the lower the radon level, the lower the risk.

Why Long-Term Testing Matters for Interpreting Results

Radon levels shift daily and seasonally, influenced by weather, ventilation, and even wind pressure. A short-term test — run over a few days — can easily overstate or understate a home’s true annual average.

That’s why Health Canada recommends testing for at least three months, ideally during the fall and winter heating season, when homes are sealed up and radon levels tend to be more consistent. A long-term result is what should actually be compared against the 200 Bq/m³ guideline — a single high or low short-term reading isn’t a reliable basis for decision-making either way.

What Should You Do If Your Result Meets or Exceeds the Guideline?

If a long-term test comes back at or above 200 Bq/m³, the recommended next step is corrective action — and generally, the higher the level, the sooner action should be taken. The most common and effective solution is active soil depressurization (ASD), a mitigation system that draws radon gas from beneath the foundation and vents it safely outside before it can enter the home.

A C-NRPP certified professional can assess your home’s foundation and recommend the right approach. After installation, a follow-up test confirms the system is working and that radon levels have dropped as expected.

Frequently Asked Questions

What does 200 Bq/m³ actually mean? It’s the long-term average radon concentration at which Health Canada recommends taking corrective action in a home’s living areas.

Is a radon level under 200 Bq/m³ completely safe? Not entirely — risk decreases as radon levels decrease, but no level is considered completely risk-free. Being under the guideline simply means action isn’t required.

Why is Canada’s guideline different from the U.S. guideline? Canada’s 200 Bq/m³ and the U.S. EPA’s ~148 Bq/m³ both fall within the WHO’s recommended range; the difference reflects how each country balances feasibility and public health resources, not a disagreement on the underlying science.

Does a short-term test tell me if I’m above or below the guideline? Not reliably. Because radon levels fluctuate, a long-term test of at least three months gives the most accurate comparison to the guideline.

What happens if my home tests above the guideline? Health Canada recommends corrective action, most commonly a mitigation system such as active soil depressurization, followed by retesting to confirm the reduction.

The Bottom Line

Health Canada’s 200 Bq/m³ guideline is a science-based benchmark for reducing risk — not a strict line between safe and dangerous. Because risk decreases as radon levels decrease, lower is generally better regardless of where a home falls relative to the guideline. The only way to know where your home actually stands is with a proper long-term test, and if your result meets or exceeds the guideline, effective mitigation is available.

Not sure how to interpret a result you already have, or haven’t tested yet? Book a professional long-term radon test with RadonPatrol and get a clear, accurate picture of your home’s radon levels.