An indoor air quality test measures what your senses can’t detect: excessive humidity, mold spores, carbon monoxide, radon, and volatile organic compounds. It’s performed when symptoms persist, after water damage, or before buying a home.
Measurements are taken in rooms that are normally occupied, including the basement.
Most homes do not need an annual test. There are four situations that warrant one. First, symptoms that follow the home: congestion, coughing, eye irritation, or headaches that subside when the occupants are away for a few days. The Quebec government directly links these symptoms to prolonged exposure to mold in residential settings.
Next, water damage: seepage through the foundation, sewer backup, a hole in the roof, or a frozen pipe. Mold can colonize a damp drywall panel within 24 to 48 hours. Third scenario: a persistent earthy or musty odor with no visible signs of moisture, typically in a crawlspace, an attic, or behind wall paneling. Fourth scenario: a real estate transaction or rental dispute, where a dated laboratory report serves as evidence that a visual inspection alone cannot provide.
Conversely, if a 30-cm black stain is visible behind a washing machine, an analysis is often unnecessary: the source has been identified, so it’s time to move on to correcting the issue and treating the mold.
“Air analysis” encompasses several distinct measurements, each with different methods and durations. Confusing them is the leading cause of unusable results.
| Parameter | Method | Sampling duration | Reference point |
|---|---|---|---|
| Relative Humidity | Hygrometer / Logger | 7 to 14 days | 30 to 50% (INSPQ) |
| Carbon dioxide (CO₂) | Infrared sensor | 24 to 72 hours | 1,000 ppm over 24 hours (Health Canada) |
| Mold Spores | Volumetric sampling on cassette | 5 to 15 minutes per room | Comparison with outdoor levels |
| Aerobic bacteria | Agar plating, laboratory culture | Analysis takes 3 to 7 days | Comparison with external samples |
| Radon | Passive alpha detector | At least 3 months | 200 Bq/m³ (Health Canada) |
| Carbon monoxide (CO) | Electrochemical detector | Continuous measurement | Any sustained reading requires venting |
CO₂ deserves some clarification: it is not toxic at residential concentrations, but it is the best indirect indicator of air exchange rate. Health Canada explains this in its guidelines on residential indoor air quality. A closed bedroom where levels rise to 1,800 ppm at night does not indicate the presence of a toxin; it indicates that fresh air is not entering the room.
A typical inspection of a single-family home lasts between 90 minutes and 3 hours and always follows the same sequence. First, a visual and olfactory inspection is conducted, room by room, including the basement, crawl space, and attic. Next, we use a thermo-hygrometer and a moisture meter to test suspicious materials. Only then do we take air samples, because the results can only be interpreted in light of what we’ve observed.
Two rules determine the validity of a fungal sample. An outdoor reference sample must be collected on the same day, at the same time: without it, an indoor count is meaningless, since spores occur naturally everywhere. Additionally, doors and windows must remain closed for 12 to 24 hours prior to the visit, with mechanical ventilation operating normally.
When the suspected source is located within the distribution system, air sampling is accompanied by a robotic inspection of the ducts: the camera reveals buildup, construction debris, or traces of water, which the laboratory will simply confirm.
Volumetric sampling requires a known flow rate and an external reference sample.
A bacteriological and fungal analysis report does not provide a score out of 100. It provides concentrations in CFU/m³ or spores/m³, a breakdown by genus, and the same count for outdoor samples. Interpretation is based on three questions.
| What the report shows | Common interpretation | Action |
|---|---|---|
| Interior is inferior to or comparable to the exterior; same types | Normal condition | Monitor humidity; no work required |
| Upper Interior, same dominant genres | Accumulation, often linked to insufficient ventilation | Improve air circulation, clean |
| Genus associated with persistent moisture (Stachybotrys, Chaetomium, hydrophilic Aspergillus ) | Active growth within the building | Locate and cut off the water source; decontaminate |
| Low counts but a distinct odor | Colony hidden behind a material | Targeted investigation, surface or material sampling |
The INSPQ emphasizes this point in its framework for addressing air quality and housing health: there is no universal threshold value for mold in residential settings. The assessment is based on the difference between indoor and outdoor levels, the types of mold identified, and the actual condition of the building.
Radon is a naturally occurring radioactive gas produced by the decay of uranium in the soil. It enters homes through cracks in the foundation slab, drains, and sump pits. It is odorless and colorless, and is the second leading cause of lung cancer in Canada. The federal guideline is 200 Bq/m³ for the average annual exposure in rooms that are normally occupied.
Two practical implications. A 48-hour test is not sufficient: concentrations vary by a factor of 2 to 5 depending on the season, atmospheric pressure, and ventilation operation, hence the requirement for a passive detector to be left in place for at least 3 months, ideally between November and April. And if the result exceeds 200 Bq/m³, the solution involves actively depressurizing the floor, not simply adjusting the fan.
New homes in Quebec are airtight by design, which is great for heating bills but problematic for indoor air quality. Without mechanical ventilation, moisture produced by cooking, showering, and breathing remains inside. That’s why analysis reports so often conclude with the same recommendation: run the heat-recovery ventilator continuously at a low setting and clean its filters.
The EPA prioritizes ventilation and source control over any purification system: dilute and exhaust before filtering. Specifically, in a home where testing reveals a humidity level of 62% in January, the recommended sequence is as follows.
Key figures for homes in Quebec.
Retail test kits often rely on a Petri dish left open on a counter. The result is guaranteed to be positive: spores are present in any healthy home. Without a calibrated volumetric sample or an external reference, the data cannot be interpreted, and, more importantly, it provides no information about the location of the source.
A professional service provides three things: a known sampling rate, an independent accredited laboratory, and a building inspection that links the measurement to a physical cause. For homes in the Granby and Haute-Yamaska areas,the Ventilo Exp’Air team combines analysis, duct inspection, and ventilation repairs into a single service call.
Instrument measurements (humidity, CO₂, CO) are taken on-site. Fungal and bacterial samples require laboratory culturing or microscopic counting, which generally takes 3 to 7 business days. Radon is the exception, requiring a 3-month sampling period.
No. In fact, the house should remain in its normal living condition. We simply ask that you keep the windows closed for 12 to 24 hours beforehand, avoid vacuuming right before the visit, and refrain from using scented products on the day of the test.
Indirectly. A high indoor count of hydrophilic mold species indicates active growth somewhere, but locating the source requires an inspection using a moisture meter, a thermal imaging camera, or the targeted removal of building materials. This is why an air quality analysis is never offered on its own.
There is no recommended testing frequency for a home where no symptoms are present. The analysis is typically repeated to verify that remediation work has been effective, after a new water damage incident, or when new occupants experience recurring symptoms.
Yes, when the duct system is genuinely contaminated—such as after construction work, a fire, water damage, or in an older home that has never been maintained. However, it does not solve moisture problems or inadequate ventilation. Air duct cleaning is one part of the solution, not the entire solution.
