You cannot see, smell or taste radon. If you are buying a home in Greater Sudbury, a neighbour's result or a quick look around the basement will not tell you that home's level. A properly placed, long-term test will.
Radon is a radioactive gas that can move from the ground into a building. Long-term exposure raises lung-cancer risk. I would treat it as a home-specific measurement and planning question, not as a reason to guess that an entire neighbourhood is safe or unsafe. Health Canada's radon overview explains the risk and why testing matters.
Give the test enough time
Health Canada's measurement guide recommends a test lasting three to 12 months to estimate the annual average. A long-term measurement must run for at least 91 days, with at least 91 days in the heating season recommended. If a shorter heating-season portion produces a result below the Canadian guideline, the guide says to retest in the next heating season. A short reading can be useful context, but it is not the recommended long-term result.
Put the detector in a normally occupied room on the lowest lived-in level: a place someone spends, or is expected to spend, more than four hours a day. Follow the device instructions on distance from windows, doors, vents, exterior walls, heat, humidity and other interference. Do not move the device around during the measurement. Health Canada's 2026 device guide can help you choose and place a suitable detector.
If you are buying, ask for the actual record
If the seller has tested, request the complete report, including dates, duration, room, device or laboratory, result and any mitigation or follow-up records. Check whether the room is still used the same way. A test from an unfinished basement may not answer a question about a finished bedroom today. Building or ventilation changes after the test may call for retesting.
A normal offer-condition period is often shorter than a proper long-term radon test. I would make that timing gap explicit with your real estate representative and lawyer before a condition deadline. Depending on the property and agreement, you might seek existing records, specialist advice, negotiated testing access or a post-possession test plan. A quick number should not be presented as a definitive annual average, and contract language should come from your lawyer.
Know what the result means
The Canadian guideline is 200 Bq/m³, based on the average annual level in a normally occupied area. Above that level, Health Canada recommends corrective action within one year, sooner when the level is higher. Below 200 is not a guarantee of zero risk; reducing radon as much as practicable is still sensible.
If the long-term result is above the guideline, ask a C-NRPP-certified radon mitigation professional to assess this building and recommend a solution. Sub-slab depressurization is a common method, but the design must fit the home. Keep the installation and follow-up test records, and retest after mitigation or major changes that could affect the building.
Put radon in the larger home review
- Ask for the full existing test and mitigation records, not only a number.
- Check the test duration, season and room against Health Canada's current guidance.
- Discuss the timing gap before a purchase condition expires.
- Use a qualified radon professional for measurement or mitigation questions and a lawyer for contract terms.
Radon testing is not a substitute for a home inspection in Sudbury. If renovations may change the lower level, the questions in my fixer-upper guide also belong in your planning. I can help keep those people and deadlines connected; the testing, health and contract advice should come from the appropriate professionals. This is general consumer information as of October 2026, not medical, environmental or legal advice.