What are the dangers of using a portable generator inside my garage during a winter power outage?

Running a portable generator inside your garage — even with the door open — is life-threateningly dangerous and kills Canadians every single winter. Carbon monoxide (CO) from generator exhaust is colourless and odourless, and it can reach lethal concentrations inside an enclosed or semi-enclosed space within minutes. This is not a theoretical risk; it is the leading cause of non-fire death associated with portable generators in North America, and emergency rooms across the GTA see CO poisoning cases during every major power outage.

During Toronto's 2013 ice storm, Toronto Paramedic Services and GTA hospitals treated a surge of carbon monoxide poisoning cases, many from homeowners who ran generators in attached garages, open garages, carports, or even inside the house. CO is slightly lighter than air and migrates readily through door gaps, ventilation systems, and any opening between your garage and your living space. An attached garage is essentially connected to your home's air space — the door seal between the garage and the house is not airtight, and your HVAC return air ducts may draw contaminated air directly from the garage into your living areas. Even a detached garage with the door wide open can accumulate dangerous CO levels if the generator is positioned where exhaust recirculates.

The only safe location for a portable generator is outdoors, at least 6 metres (20 feet) from any window, door, or ventilation intake, with the exhaust directed away from the home. Position it on a dry, level surface and protect it from rain and snow with a canopy or manufacturer-approved cover — never an enclosed structure. The heavy-duty extension cord or generator cord runs from the outdoor generator to your transfer switch inlet box on the exterior wall. If you do not have a transfer switch installed, you can run individual heavy-duty extension cords through a cracked window to power specific appliances — but you must never connect a generator directly to your electrical panel without a transfer switch.

The symptoms of carbon monoxide poisoning are deceptively subtle and easily mistaken for flu, fatigue, or the general malaise of being stuck at home during a power outage. Early symptoms include headache, dizziness, nausea, confusion, and drowsiness. Because CO displaces oxygen in your bloodstream, victims often become too disoriented to recognize the danger and escape. Sleeping occupants are at the highest risk — they may never wake up. Every GTA home should have carbon monoxide detectors on every level and near sleeping areas, and these detectors must have battery backup so they continue functioning during a power outage when the CO risk is greatest.

Beyond carbon monoxide, operating a generator in an enclosed space presents fire risk from fuel storage and hot exhaust surfaces. Gasoline vapours accumulating in a garage can ignite from the generator's hot exhaust manifold or a spark. Never refuel a generator while it is running or hot — shut it down, let it cool for 10 to 15 minutes, and refuel outdoors.

The safe, permanent solution is a properly installed manual transfer switch with an exterior power inlet box, allowing you to run your portable generator safely outdoors and connect it to your home's panel through a weatherproof cord. Installation costs $1,500 to $2,500 in the GTA — a modest investment compared to the catastrophic consequences of indoor generator use. For homeowners who want to eliminate the portable generator risks entirely, a permanently installed natural gas standby generator with an automatic transfer switch runs $8,000 to $15,000 and never requires manual operation, fuel handling, or outdoor setup during a storm. Toronto Electrical Repair can help you find a licensed electrician to set up safe generator connections for your home.