A Simple Garage, an Invisible Threat: The Story of a Critical HVAC Intervention in the Heart of Montréal
During a service call in the middle of February in Outremont, a densely populated residential neighbourhood in Montréal, our team at AirGreen encountered a particularly dangerous situation: a carbon monoxide (CO) leak coming from a poorly ventilated residential garage. This colourless, odourless, and potentially deadly gas had silently accumulated inside, threatening the health of the home’s occupants.
This event serves as a stark reminder that proper mechanical garage ventilation is not just a convenience—it's a vital necessity, especially in urban environments where garages are often attached to residential buildings.
The Context: A Modern Home with Overlooked Ventilation
The homeowners, a couple with two young children, had recently renovated their house, adding an attached garage for convenience. When they began experiencing persistent headaches and chronic fatigue, they consulted a doctor. Suspecting CO poisoning, the doctor advised them to have their home professionally inspected.
That’s when we were called in for a full HVAC inspection, with special focus on the garage ventilation system.
Detecting the Leak: Methodology and Swift Action
Upon arrival, we used an electronic carbon monoxide detector in various rooms throughout the home, including the garage. The results were alarming: CO levels in the garage exceeded 80 ppm (parts per million)—well beyond the recommended safety limits.
After further inspection, we identified several sources of the leak:
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A car engine left running inside the closed garage.
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No dedicated air extraction system in place.
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Poor separation between the garage and the living spaces.
The home had no mechanical exhaust fan to ensure air renewal in the garage. Even worse, the central ventilation ducts didn’t extend to this area, making it completely sealed off.
The Solution: Installing a Controlled Mechanical Ventilation System (CMV)
At AirGreen, we decided to install a dedicated ventilation system for the garage, fully compliant with Quebec Building Code standards. Here are the measures we implemented:
1. Installation of a Controlled-Flow Exhaust Fan
We selected a Vortex VTX400 model, a high-capacity exhaust fan designed specifically for residential garages. It offers an airflow rate of 395 CFM, ideal for spaces between 20 and 30 m². This fan is automatically triggered by a built-in CO detector.
2. Addition of a Connected CO Detector
To further enhance safety, we installed a connected carbon monoxide detector linked to the ventilation system. As soon as CO levels hit 25 ppm, the ventilation kicks in automatically. The system is also connected to a mobile app, allowing homeowners to monitor air quality in real time.
3. Sealing and Separation
We reinforced the separation between the garage and the living areas by adding fire-rated doors with weather stripping and fully sealing any cracks in the walls and ceilings.
Results After the Intervention: Safety Restored, Comfort Improved
A few days after the installation, a new air quality check showed CO levels had dropped to below 5 ppm—a return to safe levels. The occupants’ symptoms disappeared, and the garage can now be used safely, even in winter.
What This Story Teaches Us About the Importance of Garage Ventilation
Many homeowners in Montréal, Laval, Longueuil, and areas of the North Shore and South Shore underestimate the dangers of poor garage ventilation, especially when the garage is attached to the home. Carbon monoxide can quickly seep into living areas, causing severe symptoms and even death in extreme cases.
At AirGreen, we constantly stress that every garage should have an independent mechanical ventilation system, especially if it’s heated or regularly used as a workspace or winter parking.
Regulatory Standards in Quebec
According to the RBQ (Régie du bâtiment du Québec), any attached garage must:
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Be ventilated at a minimum rate of 0.5 air changes per hour.
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Have an independent mechanical ventilation system.
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Be isolated from living spaces with fire-resistant materials.
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Be equipped with CO and smoke detectors nearby.
Practical Tips to Avoid Risk
Here are some recommendations we often share with our clients:
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Never run a car engine inside a closed garage.
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Install CO detectors both inside and outside the garage.
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Maintain ventilation systems regularly.
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Check ventilation ducts and seals at least once a year.
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Always work with certified HVAC professionals for renovation or installation projects.
AirGreen: Your Trusted Safety Partner for Residential HVAC Projects
At AirGreen, we’ve completed dozens of similar interventions in single-family homes, plexes, and condos throughout Montréal, Laval, Longueuil, the North Shore, and the South Shore. Every intervention is an opportunity to protect families and provide a healthy, comfortable environment.
Thanks to our tailored approach, our technical expertise in mechanical ventilation systems, and our deep knowledge of Quebec’s safety regulations, we offer our clients long-lasting peace of mind.
Conclusion: Never Underestimate the Dangers You Can’t See
This story about a carbon monoxide leak highlights an important truth: the most serious threats are often invisible and silent. Proper garage ventilation, far from being just a comfort feature, is a true safety barrier. We encourage all homeowners to have their installations inspected, ask the right questions, and work with qualified professionals like AirGreen.