Most Ontario homeowners spend roughly 90% of their time indoors, yet fewer than half have taken any steps to assess or improve their indoor air quality. A comprehensive 2026 report compiled by Platinum Air Care, a family-owned company serving over 30,000 homeowners across Southwestern Ontario since 1999, reveals a troubling gap between the time Canadians spend breathing indoor air and their awareness of what they're actually breathing .

What's Really Happening Inside Ontario Homes?

The report, which draws on data from Health Canada, Environment and Climate Change Canada, Statistics Canada, and peer-reviewed research, paints a concerning picture of indoor air quality across the province. Ontario's housing stock is uniquely vulnerable to indoor pollution because of how homes are designed and heated. Approximately 67% of Ontario households heat with natural gas, and 75% use forced-air furnace systems . These combustion-based systems can introduce nitrogen dioxide and other byproducts into the home when improperly maintained or inadequately vented.

The problem is compounded by Ontario's climate and building design. Cold winters drive the construction of tightly sealed building envelopes meant to retain heat, and the province's prevalence of full basements creates ground-contact living spaces where soil gases, including radon, can accumulate. Health Canada and the U.S. Environmental Protection Agency (EPA) have both noted that indoor air can be two to five times more polluted than outdoor air, even in industrialized urban areas .

Put these factors together, and indoor pollutant concentrations in Ontario homes can substantially exceed outdoor levels. Approximately 3.8 million Ontario residential natural gas customers have an added concern: any gas-fired furnace, water heater, stove, or fireplace is a potential source of combustion byproducts, including carbon monoxide, nitrogen dioxide, and fine particulate matter .

How Are Wildfires Changing Indoor Air Quality?

Canada's 2023 wildfire season was unprecedented and had continental impacts on indoor air quality. Approximately 15 million hectares burned nationally, more than seven times the historical annual average of roughly 2.5 million hectares and more than double the previous record of 6.7 million hectares set in 1989 . The smoke impacts were staggering: Environment and Climate Change Canada issued approximately 5,000 air quality alerts during 2023, compared to a national annual average of roughly 1,300 between 2017 and 2022 .

Southern Ontario experienced two major smoke episodes in June 2023 that had measurable health consequences. A peer-reviewed study published in the Canadian Medical Association Journal found that population-weighted daily mean PM2.5 (fine particulate matter) concentrations across Ontario surged from a pre-smoke baseline of 7.4 micrograms per cubic meter to 53.2 micrograms per cubic meter during the first episode and 65.3 micrograms per cubic meter during the second . For context, the World Health Organization's 24-hour PM2.5 guideline is 15 micrograms per cubic meter, meaning Ontario's air during these episodes was more than four times the recommended safe level.

The health impacts were immediate and measurable. During the June 2023 wildfire smoke episodes, asthma-related emergency department visits rose measurably across Ontario . An estimated 354 million people in North America and Europe experienced at least one day where PM2.5 concentrations exceeded healthy levels, with Canadians experiencing an average of 27 such days .

The Radon Problem Ontario Homeowners Are Ignoring

While wildfire smoke captures headlines, a silent threat lurks in Ontario basements: radon. Approximately 1 in 5 Canadian homes (17.8%) have radon levels at or above Health Canada's guideline of 200 becquerels per cubic meter, a measure of radioactive decay . In Ontario specifically, 13 of 36 health regions had more than 10% of homes exceeding the guideline .

The stakes are significant. Radon accounts for an estimated 850 lung cancer deaths in Ontario each year, and approximately 3,200 radon-attributable lung cancer deaths annually across Canada, representing 16% of all lung cancer deaths . Despite this, most Ontario homeowners have never tested for radon. The problem is compounded by the fact that radon is invisible, odorless, and tasteless, making it impossible to detect without specialized testing.

Steps to Reduce Your Indoor Air Quality Risks

• Test for radon: Contact a certified radon testing professional to measure radon levels in your home, particularly in basements and below-grade living spaces. Testing is the only way to know if your home exceeds Health Canada's guideline of 200 becquerels per cubic meter.
• Maintain gas appliances: Have your furnace, water heater, stove, and fireplace inspected annually by a qualified technician to ensure proper venting and combustion air supply, which prevents the buildup of nitrogen dioxide and carbon monoxide.
• Ensure adequate ventilation: As of January 1, 2025, Ontario's updated Building Code mandates heat recovery ventilation (HRV) or energy recovery ventilation (ERV) mechanical ventilation systems in every new home. If you have an older home, consult with an HVAC professional about whether your home has adequate mechanical ventilation or if upgrades are needed.
• Monitor outdoor air quality alerts: During wildfire season, check Environment and Climate Change Canada's air quality alerts and consider keeping windows closed on days when PM2.5 concentrations are elevated.
• Assess your home's airtightness: Modern, energy-efficient construction creates airtight envelopes that cannot ventilate themselves naturally. If your home is tightly sealed, mechanical fresh-air systems are essential to prevent indoor pollutant accumulation.

The 2026 Ontario Indoor Air Quality Report highlights a critical gap in homeowner awareness. Fewer than half of Ontario homeowners have taken any steps to assess or improve their indoor air quality, despite spending the vast majority of their time indoors . The report's findings suggest that both individual action and policy changes are necessary to address indoor air quality risks across the province.

Ontario's updated Building Code requirement for mechanical ventilation in new homes represents a significant policy shift, acknowledging that modern construction practices require active air management. However, the existing housing stock, which makes up the vast majority of Ontario homes, remains largely unaddressed. Homeowners in older homes should prioritize radon testing and furnace maintenance as immediate steps to reduce their exposure to indoor air pollutants.