Radon Levels Chart: What Bq/m³ Readings Mean in Canada

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A note before you read. This article is general information for Canadian homeowners — not medical, legal, financial, or warranty advice. Radon results are reported against Health Canada's guideline of 200 Bq/m³. RadonTest.ca coordinates kit logistics and sample submission only; we do not interpret your results or assess your health. All analysis is performed independently by a C-NRPP-certified laboratory.

Quick answer

A radon levels chart sorts a long-term result into bands of becquerels per cubic metre (Bq/m³) and shows what Health Canada guidance suggests for each band. The number that matters in Canada is the 200 Bq/m³ guideline. Below it, no action is recommended — but no level is risk-free, so lower is always better. Between 200 and 600 Bq/m³, Health Canada suggests reducing the level within one year; above 600 Bq/m³, the higher the level, the sooner you should act — as soon as possible. The catch worth remembering: a chart only means something if the number you place on it comes from a long-term test of at least 91 days. A short "snapshot" reading can drop you into the wrong band entirely.

The radon levels chart (Bq/m³ with pCi/L conversion)

Radon is measured in becquerels per cubic metre of air (Bq/m³). You may also see American readings in picocuries per litre (pCi/L); the two convert cleanly, because 1 pCi/L = 37 Bq/m³. The chart below places the common ranges side by side with their approximate pCi/L equivalents and, most importantly, with what each range means and what Health Canada guidance recommends you do about it.

Long-term reading Approx. pCi/L What the number means What Health Canada guidance suggests
Below 100 Bq/m³ Below ~2.7 Below the World Health Organization's 100 Bq/m³ reference level — among the lower readings Canadian homes report No action recommended. Lower is always better, and no level is risk-free; retest after major renovations.
100–200 Bq/m³ ~2.7–5.4 Below Canada's 200 Bq/m³ guideline, but not zero No action required. Some homeowners still choose to reduce further.
200–600 Bq/m³ ~5.4–16.2 At or above the Canadian guideline Reduce the level — Health Canada suggests acting within 1 year.
Above 600 Bq/m³ Above ~16.2 Well above the guideline Reduce the level — still within 1 year, but the higher the level, the sooner you should act (as soon as possible).

A few things stand out the moment you read the chart this way. There is no row labelled "risk-free," and there is no row labelled "dangerous." Instead, the bands describe how soon action is recommended, because radon risk builds up gradually with exposure over years rather than switching on at a single line. For a fuller walk-through of a result once it lands in one of these bands, see our guide to reading your radon test results.

Why there is no "risk-free" line on the chart

It is tempting to want a single number below which a home is "in the clear." Radon does not work that way. It is a naturally occurring radioactive gas, present in trace amounts in outdoor air everywhere, and the health risk it carries rises with the concentration you breathe and the length of time you breathe it. That means a reading of 90 Bq/m³ carries somewhat less risk than 190 Bq/m³, which carries less than 400 Bq/m³ — a slope, not a cliff.

This is why we never describe a result below 200 Bq/m³ as "risk-free." The accurate phrase is "no action recommended": Health Canada's 200 Bq/m³ guideline is the point at which the agency recommends you take steps to reduce the level, not a wall separating harmless air from harmful air. A home at 150 Bq/m³ is below the guideline and needs no remediation, yet its air is not radon-free, and lowering it further is still a reasonable goal if it can be done easily. If you have ever wondered what is a dangerous radon level, the honest answer is that Canada does not use that word — it uses an action guideline, and the higher above it you sit, the sooner action is advised. Our comparison of Health Canada, WHO and U.S. guideline levels unpacks why different bodies draw the line in different places.

Bq/m³ versus pCi/L — reading American charts

Because so much radon information online is American, homeowners often stumble onto charts built around pCi/L and the U.S. action level of 4 pCi/L. Converting keeps you out of trouble: at 37 Bq/m³ per pCi/L, the U.S. 4 pCi/L action level works out to roughly 148 Bq/m³, which is below Canada's 200 Bq/m³ guideline. In other words, the two countries set their action points at different concentrations, so you cannot read one country's "act now" colour on the other country's number. When you receive a Canadian Certificate of Analysis, it is reported in Bq/m³ against the 200 Bq/m³ guideline — that is the chart to use. Keep the conversion handy only for translating American figures you come across, and see acceptable radon levels in Canada for how the Canadian guideline is meant to be applied.

A basement radon level chart uses the same bands — with one caveat

People searching for a basement radon level chart are usually asking a fair question: basements almost always read higher than upstairs, because they sit closest to the soil where radon originates and often have the cracks, sumps and floor-wall joints that let soil gas in. So should you judge a basement by a different, more forgiving chart?

No. The bands above apply to whatever reading you take — a basement result of 250 Bq/m³ is at or above the guideline exactly the way a main-floor result of 250 Bq/m³ would be. What changes is where you should measure. Health Canada's method is to test the lowest level you occupy for more than about four hours a day. If your basement is a finished family room, office or bedroom, that is the level to test and to place on the chart. If nobody spends meaningful time down there, you would test the lowest lived-in level above it instead. The chart does not soften for basements; it simply expects the detector to sit where life actually happens.

The chart is only as good as the test behind it

Here is the part that quietly decides everything: the band you land in depends entirely on the quality of the measurement. Radon concentrations swing hour to hour and day to day with weather, wind, and whether the furnace is running. A short test caught during a calm, mild stretch can read far lower than the home's true average — and a short test during a cold snap can spike the other way. Either way, you risk placing a misleading number on the chart and making the wrong call.

That is why Health Canada recommends a long-term test using an alpha-track detector left in place for at least 91 days. Ninety-one-plus days of continuous measurement averages out the short-term noise and produces a number that genuinely represents your home — the only kind of number worth charting. The heating season (roughly late fall through winter) is the ideal window, because homes are closed up and levels tend to run highest, but updated Health Canada guidance now allows testing at any time of year, so the best time to start is simply whenever you are ready. For the full method and placement rules, see our summary of Health Canada's testing guidance.

What to do once you know your band

If your long-term result lands below 200 Bq/m³, no action is recommended today; keep the result on file and retest after any major renovation, foundation work, or change to how you heat and ventilate the home. If it lands at or above 200 Bq/m³, the fix is well understood and, in most homes, quick: a certified professional installs a mitigation system that in most cases lowers the level by more than 80%. Our overview of how radon mitigation works explains the standard approach, and what to do if your radon level is above 200 walks through the next steps and the one-year timeline from the chart.

FAQ

What is a dangerous radon level? Canada does not label any single number "dangerous" or "risk-free." Radon risk rises gradually with concentration and years of exposure. Health Canada uses a 200 Bq/m³ action guideline: at or above it, reducing the level is recommended, and the higher above it you sit, the sooner action is advised.

Is a reading below 200 Bq/m³ risk-free? We do not call it risk-free. A result below the guideline means no action is recommended at this time — not that the air is radon-free. Lower is always better, and there is no risk-free level.

How do I convert my radon reading between Bq/m³ and pCi/L? Use 1 pCi/L = 37 Bq/m³. So 100 Bq/m³ is about 2.7 pCi/L, 200 Bq/m³ is about 5.4 pCi/L, and 600 Bq/m³ is about 16.2 pCi/L. Canadian results are reported in Bq/m³ against the 200 Bq/m³ guideline. Prefer a tool? The Bq/m³ ↔ pCi/L converter on our radon map converts any reading instantly.

Should I use a different chart for a basement reading? No. The same bands apply to any reading. Test the lowest level you occupy more than about four hours a day; if that is a finished basement, use its reading. Basements often read higher, but the guideline does not change for them.

My result is between 200 and 600 Bq/m³ — how urgent is it? Health Canada suggests reducing the level within one year. Above 600 Bq/m³, the higher the level, the sooner you should act — as soon as possible. Neither is an emergency, but both call for a plan and a certified mitigation professional.

Why does my reading change every time I look at a monitor? Radon fluctuates constantly with weather and how the home is running. That is exactly why a long-term test of at least 91 days is used to place a reliable number on the chart, rather than a short snapshot.

Does a low number mean I never have to test again? No. Renovations, foundation changes, new ventilation, and years of settling can all move your level. Retest after major changes, and periodically even without them.

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Put a real number on the chart

A chart is only useful once you have a valid reading to place on it — and the only way to get one is a long-term test of your own home. Order the RadonTest.ca radon test kit. It is all-inclusive: a C-NRPP-listed long-term (alpha-track) detector, tracked shipping both ways, analysis by a Canadian C-NRPP-certified laboratory, and your official Certificate of Analysis reported in Bq/m³ against Health Canada's 200 Bq/m³ guideline. Test your home, find your band, and get your kit today.

RadonTest.ca does not diagnose, treat, or prevent disease, and is not affiliated with Health Canada or C-NRPP.

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