An extreme case that highlights the importance of HVAC maintenance and vigilance in residential buildings across Greater Montréal
At AirGreen, we’re used to handling complex technical situations. But some service calls go well beyond the norm. In this article, we share a real-life case that happened in Laval, exposing the risks of a neglected wall-mounted air conditioner that had been running unnoticed for years. This story demonstrates the vital importance of regular HVAC maintenance, both for the health and safety of building occupants.
The context: a strange smell in a residential building
It all started with an urgent call from a small rental building in the Chomedey neighborhood of Laval. Several tenants were complaining about persistent, unusual odors in common areas, accompanied by recurring headaches and a sense of stale air. The property manager had already contacted cleaning services and even municipal workers, with no resolution.
When we arrived on-site, we immediately suspected an issue involving an unmaintained HVAC unit. A full inspection of each apartment was necessary.
The discovery: a 12,000 BTU Midea wall-mounted unit unused for 6 years
In one apartment that had been vacant for several months, we found a 12,000 BTU Midea wall-mounted air conditioner, partially hidden behind a piece of furniture. According to the owner, the unit hadn’t been used or checked in over six years. To our surprise, it was still plugged in and running in constant fan mode, circulating air through a filter that was completely clogged with mold.
Most alarming of all: visible colonies of spores were growing inside the air outlet, along with a constant flow of stagnant water that hadn’t drained in years. The unit had essentially become a source of indoor air contamination.
Our response: emergency remediation
Given the urgency of the situation, we immediately took the following actions:
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Safely disconnected and removed the Midea unit.
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Fully disinfected the affected area using certified antibacterial products.
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Inspected the integrity of walls, ducts, and electrical wiring.
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Preemptively cleaned other wall-mounted units in the building.
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Issued a full sanitary report sent to the property management board.
We also advised the building manager to implement a mandatory annual HVAC maintenance program, with tracking, for every wall-mounted air conditioner on the premises.
A disaster narrowly avoided
Without our intervention, this forgotten wall-mounted air conditioner could have continued spreading harmful contaminants throughout the building. Here’s what could have happened:
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Mold spores spreading through ducts and walls.
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Indoor air contamination, leading to severe respiratory issues for tenants.
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Excessive condensation and structural damage to the surrounding areas.
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Violation of health codes, exposing the owner to legal liability.
This extreme case proves that HVAC maintenance should never be seen as a formality—it is a core part of responsible property management.
Practical tips to prevent this type of incident
Here are our recommendations for property owners and building managers:
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Keep a detailed record of all installed HVAC units by apartment.
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Label wall-mounted units with installation date and maintenance history.
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Schedule mandatory annual inspections, even in vacant units.
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Ensure that all wall-mounted units are fully accessible for servicing.
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Choose recent models with automatic maintenance alerts (e.g., Fujitsu KWL, Gree Lomo, or Sharp ZU1).
Why choose AirGreen for your HVAC installations and maintenance
At AirGreen, we’ve developed a rigorous inspection and maintenance process for wall-mounted air conditioners, tailored to the realities of residential buildings in Laval, Montréal, Longueuil, the North Shore, and the South Shore.
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Thorough inspection of indoor and outdoor units.
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Deep cleaning of filters, condensate trays, and drainage circuits.
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Performance diagnostics (pressure, noise level, airflow).
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Software updates (where applicable) for smart models.
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Assessment of LogisVert grant eligibility in the case of replacements.
Testimonial from the property manager
“I never would’ve imagined that an old forgotten AC unit could pose such a threat. AirGreen acted quickly, efficiently, and discreetly. Thanks to them, we avoided a health crisis, and now we have a maintenance protocol in place.”
A clear message for the entire property management industry
Whether you’re an owner-occupant, building manager, or developer, this case in Laval should serve as a warning. Never underestimate the importance of HVAC maintenance, even for small units like wall-mounted air conditioners.
An inactive unit doesn’t mean it’s risk-free. That’s why at AirGreen, we also offer preventive maintenance packages, tailored for multi-unit buildings, condos, or rental properties.
Conclusion: a simple oversight can lead to serious consequences
The case of the forgotten wall-mounted air conditioner in Laval reminds us that a neglected unit can become a latent health hazard. Thanks to our intervention, an invisible problem was turned into a sustainable, well-managed solution, benefiting all residents.
To ensure air quality, the longevity of your HVAC systems, and your building’s regulatory compliance, don’t wait for an emergency to happen.
Contact AirGreen now for a professional inspection, preventive maintenance, or a compliant and grant-eligible replacement.