The things people actually ask, answered plainly, with no attempt to frighten anyone into buying something.
Radon is a radioactive gas produced by uranium breaking down in soil and rock. It is invisible, odourless and tasteless. Outdoors it disperses harmlessly. Indoors it can accumulate, because a heated building draws air upward and pulls soil gas in through the foundation with it.
It is the second leading cause of lung cancer after smoking, and the leading cause among people who have never smoked. The risk comes from long exposure rather than any single day, which is why the guidelines are written as annual averages and why nobody needs to panic about a reading, only to act on it.
Through the ground floor. Cracks in a slab, gaps around service pipes, sump pits, crawlspaces, unfinished floors. Warm air rising inside creates a slight negative pressure at the bottom of the house, and that pulls soil gas in. This is also why radon is generally higher in winter, and higher in newer, tighter houses that leak less.
No. It is a sign of what is in the ground under it. Two identical houses on the same street can read very differently, and a new well-built house can read higher than an old draughty one precisely because it is better sealed. It is not a defect and it is not anyone's fault.
With a long-term test, at least three months and ideally over the heating season, in the lowest level of the house you actually spend time in. You can buy a kit and do it yourself, or have a C-NRPP certified measurement professional do it. Both are valid; the certified route matters more when the result has to satisfy somebody else, such as a buyer.
Because radon swings enormously day to day with weather, wind, and how often the doors have been open. A short test tells you about a few days, not about the house. Every guideline in the world is written in terms of long-term averages for that reason. Short tests have their place in a property transaction where there is no time for anything else, but the number they produce should be treated as a prompt to test properly, not as the answer.
A long-term do-it-yourself kit is usually somewhere around fifty dollars including the lab analysis. A certified professional placing and interpreting the test costs more, and how much varies by company and by what else is involved. Ask two or three; it is a small enough job that quotes differ more than you would expect.
First, do not panic. Radon risk is cumulative over years, so a reading of 400 does not mean anything is happening to you this week. Second, get it fixed. Health Canada suggests acting within two years for readings between 200 and 600, and within a year above 600. Lower is better at any level, and the fix works.
In most houses, sub-slab depressurization. A pipe is run from under the floor slab to above the roofline, with a fan on it that runs continuously and vents soil gas outside before it can enter. It is a day's work in a typical home, it is not structural, and it routinely cuts levels by most of the way. Ask for a re-test afterwards to confirm what it achieved.
It varies with the house, particularly the foundation type and where the pipe can run. Get more than one quote from C-NRPP certified companies, and ask whether the price includes a confirmation test. A quote that includes proof the system worked is worth more than one that does not.
That it is fixable, quickly, and that it does not have to end the deal. The practical problem is the clock, because a proper test takes months and a possession date does not wait. In practice a short-term test is what gets used, with its limitations understood on both sides, and mitigation is a days-long job rather than a months-long one. Ask any company you approach whether they can work to your closing date; some can and some cannot, and it is worth asking first.
There is no rule. It is negotiated, like any other condition, and it goes all three ways depending on the market and how the inspection was worded. What helps is knowing the actual cost early, because a number turns an open-ended worry into an ordinary line item.
No, and this is the single most misunderstood thing about radon. Neighbouring houses regularly differ by a factor of five or more. Area data tells you how likely a problem is, never whether you have one. It is why we show sample sizes on every figure on this site and why no map, including ours, is a substitute for testing your own house.
No measured threshold exists below which the risk is zero. Canada acts at 200 Bq/m3, the US EPA at about 148, and the World Health Organization sets a reference level of 100. Those are action levels, meaning the point at which fixing it is clearly worthwhile, not a boundary between safe and unsafe. Our full comparison is here: /what-is-a-safe-radon-level/
No. Radon is a gas that comes in continuously from the ground, so filtering the air in the room does not address the source. Neither do houseplants. The two things that work are reducing what comes in and venting it before it gets in, which is what a mitigation system does.
It lowers readings while they are open, and the effect ends when you close them. In a Canadian winter that is not a plan. It is also why a test taken during a week of open windows understates the house.
Canada and most of the world use becquerels per cubic metre, written Bq/m3. The United States uses picocuries per litre, pCi/L. One pCi/L is about 37 Bq/m3, so the US action level of 4 pCi/L is about 148 Bq/m3, and Canada's 200 Bq/m3 is about 5.4 pCi/L.
The Canadian National Radon Proficiency Program, C-NRPP, is the only radon certification recognised in Canada. It certifies separately for measurement and for mitigation, which is worth knowing, because a company certified to test is not necessarily certified to fix. Our Calgary list is split on exactly that line: /calgary/certified-companies/
Five of these questions have enough to say that they have their own page:
Ask us and we will add it. Contact page is here. If it is a question about your own house rather than about radon in general, the honest answer will almost always be to test the house, because no general information can describe a specific building.
Sources. Health Canada radon guidance and published measurement data; the 2024 Cross-Canada Survey of Radon; World Health Organization Handbook on Indoor Radon; United States Environmental Protection Agency; Canadian National Radon Proficiency Program. Costs described here are general ranges, not quotes, and vary by house and company.