Spontaneous Combustion, Propane, and Battery Fires
Oily rags are one of the most genuinely surprising fire hazards in a home, because the mechanism is counterintuitive: the rags don't need a spark. Rags soaked in oil-based stains, varnishes, linseed oil, teak oil, or similar drying oils undergo an exothermic oxidation reaction as the oil cures. In a wadded-up or piled configuration, that heat can't escape — and if conditions are right, the rag pile can reach ignition temperature entirely on its own. The fix is specific: spread used rags flat in a single layer outdoors until fully dry before disposal, or store them in a metal container with a tight-fitting lid until they can go to a hazardous waste facility. Guidance from the Canadian Centre for Occupational Health and Safety explains the mechanism clearly.
Propane cylinders for BBQs are a very common item stored in attached garages, and most fire safety guidance recommends against it. Even a small leak from a cylinder valve in an enclosed space can create an explosive fuel-air mixture; attached garages have ignition sources — water heaters, vehicle ignitions, power tools, furnaces with pilot lights — that a propane accumulation can find. Store cylinders outdoors, upright, in a shaded and well-ventilated location, away from building openings and any ignition sources. For a broader look at CO risks in the home — including garage sources — the 15 carbon monoxide safety facts every Canadian homeowner should know is worth reading alongside this section.
E-bike and power tool battery charging has become a new chapter in garage fire safety over the last several years. Lithium-ion batteries used in these devices can enter thermal runaway — a rapid, self-sustaining overheating reaction — if they're damaged, charged with the wrong charger, or connected to an overloaded outlet. Charge on a concrete floor or metal rack, not on cardboard, wood, or plastic shelving. Use only the charger that came with the device or one explicitly approved by the manufacturer. Don't charge overnight or when you're away. And if a battery shows swelling, unusual heat, a chemical smell, or visible distortion, stop using it and contact the manufacturer before attempting disposal.
Sawdust accumulation around stationary power tools deserves a mention: fine sawdust around an electric motor is flammable and can be ignited by a spark from the motor itself. Clean work surfaces and the areas around motors regularly.