Radon and older adults: what to check at home, with a checklist

Why radon matters in later life

Radon harm comes from the total amount breathed over years, and it can’t be reversed. How radon damage works. For someone who has lived in the same house for decades, that total may already be large. It doesn’t make testing pointless. The risk still depends on how much more is breathed, so stopping new exposure helps, and it helps most for smokers and former smokers, whose risk is already many times higher.

The benefit is also a matter of time: cancer takes years to develop, so lowering radon generally helps a 40-year-old more, in absolute terms, than an 85-year-old. If someone expects many more years in the home, or lives with a smoker, it’s still worth doing.

Situations that change the picture

• Moving the bedroom downstairs. A basement or ground-floor bedroom added to avoid stairs puts someone in the lowest, highest-radon level for around eight hours a night.
• A basement suite for a parent. Secondary units are often the lowest part of the house, and may be someone’s whole home. Which rooms matter most.
• Downsizing to a bungalow or townhouse. Slab-on-grade homes have living space directly on the ground. Neighbours’ results, and the age of the home, don’t predict yours.
• Staying home most of the day. Retirees, caregivers and anyone who’s housebound accumulate the most hours in the home.
• A history of smoking. Radon and smoking multiply each other’s effects. Former smokers remain at higher risk and benefit from lowering radon.
• Renting. The landlord arranges testing and mitigation as a building improvement. Ask for existing results in writing.

Radon checklist

• List the rooms where you spend the most hoursIncluding where you sleep. If one is on the lowest level, that’s where the detector goes.
• Run a long-term test of at least 91 days, ideally between October and AprilIf the house was tested before 2007, or only with a short test when it was bought, test again. Why.
• If it’s over 200 Bq/m³, plan mitigationWithin two years for 200–600 Bq/m³, within one year above 600. Most installs are one day, and typical costs are on the cost guide.
• Test a basement suite or in-law unit separatelyTest the unit itself, not only the house.
• Retest after renovations and equipment changesFinishing a basement, new windows, a new furnace or changes to ventilation can all change radon levels.
• If there’s a radon system, check the manometer, and retest every few yearsLevel fluid in the U-tube means the fan may have stopped. Ask a family member to check it too.
• If you smoke or used to, talk to your doctor about lung health and screeningThere’s no medical test for radon exposure. Screening eligibility depends on age and smoking history.
• Keep a copy of results and mitigation recordsUseful for the next owner, a landlord or a care provider.

The rest of the home

• Carbon monoxide alarms on every storey and near sleeping areasSince January 1, 2026, Ontario homes with a fuel-burning appliance, fireplace or attached garage need one on every storey, as well as next to sleeping areas. Replace expired units.
• Working smoke alarms on every level and outside sleeping areasTest them, and make sure the sound reaches the bedroom with the door closed.
• Tap water at 49 °C or lowerHealth Canada’s guidance is an anti-scald valve at 49 °C, with the water heater kept at 60 °C to control Legionella bacteria.

This is a home safety checklist, not medical advice. For questions about lung health, ask your doctor.

Common questions