Radon Testing & Mitigation in London, ON
London, Ontario, has seen growing awareness of residential radon risk. While southwestern Ontario's geology is less uranium-rich than the Shield, London's mix of older housing stock, newer energy-efficient builds, and a high proportion of finished basements contributes to measurable radon levels in a significant number of homes.
Why Radon Is a Concern in London
London sits on Devonian limestone and shale, with a glacial till overburden. These formations contain enough radium to produce radon, and London's heavy clay soils — while slow to allow radon movement — concentrate it once it reaches the soil-to-foundation interface. Homes in Byron, Old South, and North London have reported above-average levels.
Radon is a colourless, odourless radioactive gas produced by the natural decay of uranium in soil and rock. It enters homes through foundation cracks, pipe penetrations, sump pits, and floor drains. Once inside, it accumulates — especially in basements and lower-level living areas — and poses a serious long-term lung cancer risk. Radon is the second-leading cause of lung cancer in Canada, responsible for approximately 3,200 deaths each year.
Radon Levels in London
Average exposure: Moderate — above Toronto average, with localized elevations in older and newer subdivisions alike
Health Canada's national action level is 200 Bq/m³ (becquerels per cubic metre). Any home testing above this level should undergo radon mitigation. However, Health Canada also recommends taking action at levels above 100 Bq/m³ when mitigation is cost-effective — which it almost always is.
There is no known "safe" level of radon exposure. The lower your home's radon level, the lower your risk.
How to Test for Radon in London
The most accurate and cost-effective method for residential radon testing is a long-term alpha track test. These CPA-certified passive detectors are placed in the lowest occupied area of your home for a minimum of 90 days, capturing seasonal variation for a reliable annual average. Short-term tests (under 7 days) are acceptable for real estate transactions but should not substitute for a long-term test.
Testing is simple, DIY-friendly, and inexpensive. We recommend the Long Term Alpha Track Test Kit — certified by the Canadian Radon Proficiency Program (C-NRPP) and trusted by homeowners across Ontario.
How to test:
- Place the detector in the lowest livable area of your home (finished basement, bedroom, or office below grade)
- Leave it undisturbed for 90 days (minimum) to 12 months (ideal)
- Mail the detector to the certified lab
- Receive your results within 2–3 weeks with a full report
How to Mitigate Radon in London
If your test results exceed 200 Bq/m³ — or if you simply want to reduce exposure — sub-slab depressurization (SSD) is the gold-standard mitigation method. A certified mitigation contractor (or experienced DIYer) installs a PVC pipe through the basement floor into the soil below, connected to a continuously running radon fan. The fan creates negative pressure beneath the slab, drawing radon out before it can enter your home.
SSD systems typically reduce indoor radon by 80–99% and cost between $1,500–$3,000 installed. For DIY installations, the primary cost is the fan and fittings.
We recommend the RadonAway RP140 Energy Star — a professional-grade fan suited to London-area homes and Ontario's variable soil conditions. Browse our full radon mitigation fan selection or our complete installation parts collection.
Radon and Real Estate in London
Radon awareness is growing among London-area buyers and agents. As the Western University community — home to environmental health researchers — continues to highlight radon risk, testing is increasingly expected in local transactions.
Health Canada recommends testing any home you intend to purchase, regardless of age or construction type. Our radon and real estate guide explains when to test, how to interpret results, and how to negotiate remediation into a purchase agreement.
Frequently Asked Questions — Radon in London
- Do all homes in London have radon?
- All homes have some level of radon — the question is how much. Testing is the only way to know your home's actual level. Given London's elevated regional risk, testing is particularly important here.
- Does a newer home have less radon?
- Not necessarily. Modern energy-efficient homes are often more airtight, which can lead to higher radon accumulation. Some newer Ontario homes built since 2019 include rough-in radon systems under national building code requirements, but these must still be activated and tested.
- How long does radon mitigation take?
- A standard SSD installation takes a professional 2–4 hours. DIY installations typically take a day. The fan runs continuously at low power — most fans use 20–90 watts, less than a light bulb.
- Is radon mitigation covered by insurance or government programs?
- Radon mitigation is generally not covered by standard home insurance. No federal rebate program currently exists in Canada, though some provinces have offered periodic incentives. Check with your municipality or provincial health authority for any available local programs.
Get Started Today
Radon is the most significant environmental health risk inside your London home — and it's entirely preventable. Whether you're testing for the first time or ready to mitigate, Radon Depot has everything you need.
- Order a radon test kit — CPA-certified, lab-analyzed, Ontario-trusted
- Shop radon mitigation fans — professional-grade SSD systems
- Learn how radon mitigation works
- Read our full Radon FAQ
