How to Test Your Home’s Air Quality (and When You Actually Need To)

Testing your air quality” isn’t one test — it’s several, for different things, at wildly different costs. For most Ontario homes the honest answer is that you need two: a carbon monoxide alarm, which the law already requires, and a long-term radon test. Everything else is worth doing only when you have a specific reason.

Where we stand: Dynamic Heating and Cooling is a TSSA and ESA licensed HVAC contractor. We’re not a radon measurement company and we’re not a mold lab — those are separate certifications, and we’ll tell you below who actually holds them. What we do know is combustion safety, ventilation and humidity, because that’s the equipment we service. This guide is written from that side of the line.

What Does “Air Quality Testing” Actually Mean?

There’s no single test for “air quality.” The phrase covers at least five different things, each with its own method, cost, and level of urgency:

• Carbon monoxide — an alarm, required by Ontario law, about $40
• Radon — a long-term test kit, roughly $40–$60, and it takes three months
• Mold — comparative air sampling by a consultant, hundreds of dollars, and usually unnecessary
• VOCs and particulates — consumer monitors that show trends, not diagnoses
• Humidity — a $15 hygrometer

When a company offers you “indoor air quality testing,” ask which of these they’re actually measuring. The word covers a $40 alarm and a $600 consultant’s report equally well, and the gap between them is where people get sold things they don’t need.

Carbon Monoxide: The One Ontario Already Requires

If your home has a fuel-burning appliance, a fireplace, or an attached garage, working CO alarms are not optional — they’re the law.

Ontario’s Hawkins-Gignac Act took effect on October 15, 2014, requiring working carbon monoxide alarms adjacent to all sleeping areas in any home with a source of CO. It applies regardless of your home’s age and supersedes municipal bylaws. That covers gas, oil and propane furnaces, water heaters, gas stoves, wood and gas fireplaces, and attached garages or carports.

The rules got stricter on January 1, 2026. Changes to the Ontario Fire Code now require an alarm next to every sleeping area, plus one on every storey that doesn’t have a bedroom — not just the floors with people sleeping on them. If your alarms were installed to the old standard, you’re likely short at least one.

Non-compliance carries fines of up to $50,000 for an individual and $100,000 for a corporation.

What to know:

• CO alarms expire. Most need replacing every 7–10 years — check the label and the manufacturer’s instructions. An expired alarm is not a working alarm.
• Symptoms mimic the flu: headache, nausea, dizziness, confusion. That resemblance is exactly what makes CO dangerous.
• If your alarm sounds, leave the house and call 911. Don’t investigate. CO impairs your judgment before you notice anything is wrong.
• Hamilton Fire has noted that more than 80% of Ontario’s CO injuries and deaths happen in the home.

And the part that matters most: an alarm is your second line of defence, not your first. It tells you there’s already carbon monoxide in your house. The first line is a licensed technician inspecting your fuel-burning appliances annually to confirm they’re combusting cleanly and venting properly. The alarm catches the failure. Maintenance prevents it.

Radon: Test For It — But Not With Us

Radon is a naturally occurring radioactive gas that seeps out of the ground into buildings. It’s colourless, odourless, and the second leading cause of lung cancer in Canada after smoking, responsible for roughly 850 lung cancer deaths in Ontario every year. Roughly 4.6% of Ontarians live in homes above the guideline.

Health Canada’s guideline is 200 Becquerels per cubic metre (Bq/m³). Above that, Health Canada recommends taking action within a year — sooner the higher the reading.

How to test it properly:

• Long-term only. Minimum 91 days. Radon levels swing hour to hour and season to season, so a short test tells you almost nothing. Health Canada explicitly does not recommend testing for less than 91 days — which means those weekend “instant radon results” offers are measuring noise.
• Test during the fall or winter heating season, when your house is closed up and levels are highest.
• Put the detector on the lowest level you actually live on — where you spend at least four hours a day. A crawlspace nobody enters isn’t the answer.
• Use a device certified through the Canadian National Radon Proficiency Program (C-NRPP).

We don’t do this, and neither should most HVAC contractors. Radon measurement and mitigation are separate certifications under the C-NRPP — you can reach them at 1-855-722-6777 for a certified professional in your area. If your test comes back above 200 Bq/m³, you want a C-NRPP mitigation specialist, not us. The standard fix is sub-slab depressurization, which vents soil gas from beneath your foundation before it gets in.

Here’s the part almost nobody tells you, and it’s the reason this section exists:

Health Canada recommends re-testing your home after any renovation that changes its structure or ventilation — and it lists “installing a new furnace” by name. The same goes for energy retrofits: new windows, added insulation, air sealing.

Which means: if we just installed your furnace, or you’ve tightened up your house, your old radon number may no longer be valid. Go test it again next heating season. That’s a genuinely useful thing to know and it earns us nothing — but a home that’s more airtight is a home where soil gas has fewer places to go.

Mold: When a Test Actually Tells You Something

If you can see mold or smell it, you don’t need a test. You need to fix the water.

This is the single most common way people waste money on air quality testing. A test confirms what your eyes already told you and costs several hundred dollars to do it. Mold is not a mystery to be diagnosed — it’s a symptom of a moisture problem, and the moisture problem is what has to go. Remove the mold, find the water source, stop it. No lab required.

Testing earns its keep in narrower cases:

• You can smell something musty but can’t find it — hidden growth behind drywall or under flooring
• Someone in the house has persistent unexplained symptoms and you’ve ruled out the obvious
• You’re in a real estate transaction and need documentation
• There’s been water damage and you need to confirm a remediation actually worked

How real testing works: a professional takes air samples indoors and outdoors and compares spore counts. Outdoor air always contains mold spores — that’s normal. What matters is whether indoor levels and species are meaningfully different from the baseline outside your door. A DIY petri dish that “grows mold” proves nothing, because a petri dish left anywhere on earth grows mold.

This is an environmental consultant’s job, not an HVAC contractor’s. What we can do is address the conditions mold needs: humidity control, ventilation, and duct contamination. What we can’t do is tell you what species is in your wall.

What You Can Test Yourself

For most Ontario homes, this list is the whole job:

• CO alarms — roughly $40 each, and legally required. Every sleeping area, plus every storey without a bedroom, as of January 2026. Check the expiry date on the ones you already have.
• A long-term radon kit — roughly $40–$60. C-NRPP-certified device, 91 days minimum, fall or winter, lowest lived-in floor. Once per home, then again after major renovations or a furnace replacement.
• A hygrometer — roughly $15. Aim for somewhere around 30–50% relative humidity. Consistently above that and you’re growing mold; consistently below and you get dry sinuses, static, and cracking trim. This is the cheapest meaningful air quality instrument you can buy.

On consumer air quality monitors: the PM2.5 and VOC monitors sold as home air quality devices are useful for one thing — showing you trends. Watching the particulate count spike when you sear a steak and fall an hour later tells you your kitchen ventilation is inadequate. That’s genuinely worth knowing. What they can’t do is identify a specific contaminant or give you a number anyone would act on clinically. Treat them as a smoke signal, not a diagnosis.

When Professional Testing Is Worth Paying For

• Persistent symptoms with no visible cause — and everyone feels better when they leave the house for a few days
• A radon result above 200 Bq/m³ — that’s a C-NRPP mitigation call, not a testing call
• After significant water damage, to confirm remediation worked
• A real estate transaction where you need documentation rather than reassurance
• A commercial space with occupant complaints and a legal duty of care

Notice what isn’t on that list: general anxiety about air quality. If you have no symptoms, no visible mold, working CO alarms and a radon result under the guideline, a paid air quality assessment will almost certainly tell you your air is fine — for a few hundred dollars.

What HVAC Can and Can’t Fix

Testing tells you what’s wrong. Fixing it is a different question, and it’s worth knowing which problems are actually ours.

Things HVAC addresses:

• Ventilation — stale air, trapped moisture, and CO2 buildup in tight homes. A balanced ventilation system is the real fix here; see our guide to HRV and ERV systems.
• Filtration — dust, pollen and dander, via appropriate filter media
• Humidity — humidification in winter, dehumidification in summer
• Combustion safety — annual inspection of fuel-burning appliances, which is the actual prevention for CO
• Duct contamination — duct cleaning where there’s a genuine reason for it

Things HVAC does not fix:

• Radon — that’s sub-slab depressurization, a C-NRPP specialty
• Mold remediation — that’s a remediation contractor, plus fixing whatever let water in
• VOC sources — no filter beats not bringing the product into the house
• Structural moisture — a leaking foundation is not a ventilation problem

If you’ve tested, found something, and it lands on the first list, that’s what our indoor air quality services are for. If it lands on the second, we’ll tell you that too.

The Short Version: What Most Ontario Homes Actually Need

If you skipped to the end, here it is.

Do these two things:

• Working CO alarms. Next to every sleeping area, plus every storey without a bedroom. Not optional — Ontario law, and the requirement expanded in January 2026. Check the expiry date on the ones you have.
• One long-term radon test. C-NRPP-certified kit, 91 days minimum, fall or winter, lowest floor you actually live on. Roughly $50, once per home.

Add a $15 hygrometer if you want a third thing. Around 30–50% relative humidity. It’s the cheapest useful instrument in this whole guide.

Then stop — unless one of these is true:

• Your CO alarm sounds → leave the house, call 911
• Your radon result is above 200 Bq/m³ → call a C-NRPP mitigation specialist
• You can see or smell mold → don’t test it, find the water and fix it
• Someone’s persistently unwell and you’ve ruled out everything obvious → that’s when a professional assessment earns its cost
• You’ve replaced your furnace or tightened up your house → re-test radon next heating season

That’s the whole decision. If none of those apply, your air is almost certainly fine, and a paid assessment will spend a few hundred dollars telling you so.

And if something did turn up? That’s when to call someone. If it’s ventilation, humidity, filtration, duct contamination or combustion safety, that’s our work — see our indoor air quality services in Hamilton, or get in touch and we’ll take a look. If it’s radon or mold, we’ll tell you that and point you to the people who handle it.