One furnace symptom overrides every normal troubleshooting habit: if it smells like gas, you leave first and diagnose later, never the other way around.
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Quick answer
A gas odour near the furnace means you get out of the house first, avoid anything that could spark, and call FortisBC's emergency line from outside — before checking the thermostat, the filter, or anything else you'd normally look at with a furnace problem. Natural gas is odourless, so what you're smelling is a scent added deliberately so a leak is noticeable, and it should always be treated as real until a professional confirms otherwise.
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With almost every other furnace problem in this series, the advice starts with a few things you can safely check yourself — the thermostat, the breaker, the filter. A gas smell is the one exception, and it's worth understanding why: any of those normal checks involves flipping a switch or moving around inside a home that might have gas accumulating in it, and that's exactly the risk you want to avoid until the situation has been confirmed safe.
Natural gas has no smell of its own — the distinctive rotten-egg odour is added specifically as a warning signal, and if that's what you're noticing, treat it as genuine every time, without exception. A separate and much more common smell is a warm, dusty odour the first time a furnace fires up after sitting idle over summer, which is usually just accumulated dust on the heat exchanger burning off and clearing within a few minutes. The difference in smell is usually obvious once you know to compare them: rotten-egg sulphur versus a dry, dusty, burning-off odour that fades on its own.
Homes with a basement suite or a laneway house often have more than one household sharing the same general gas supply and mechanical space, which means everyone living on the property needs to know the same first response, not just whoever owns the house. On narrow lots, a gas meter or shutoff sitting close to a walkway or a shared fence is also worth everyone in the household being able to locate calmly, even though finding it is never the priority over simply getting out first.
After FortisBC or a technician confirms it's safe to re-enter, a licensed gas fitter traces the actual source — checking every fitting from the meter to the furnace under pressure, and reviewing the ignition sequence and venting. Most of the time it comes down to one identifiable point of failure, and you'll get a clear explanation of what was found and what fixing it involves before any repair begins.
Safety note
A gas odour near the furnace is a genuine emergency, not a troubleshooting question. Leave the home immediately, avoid switches, phones or anything that could spark, and call FortisBC's emergency line at 1-800-663-9911 from outside before doing anything else. Only a Technical Safety BC licensed gas fitter should investigate or repair the source afterward.
No — get out of the house first and call FortisBC from a safe distance. Searching for a leak, including flipping switches on or off along the way, is exactly what the first steps are meant to prevent.
A brief dusty or warm smell as accumulated dust burns off the heat exchanger is common and usually clears within a few minutes. A rotten-egg sulphur smell is a different thing entirely and should always be treated as a real concern.
Only if the shutoff is right on your way out and doing so causes no delay. Getting everyone out of the house quickly matters more than stopping to shut off the valve yourself.
FortisBC responds to confirm safety and can isolate the gas supply if needed, but fixing the specific cause — a fitting, a valve, an ignition delay — is done afterward by a licensed gas fitter.
Leave and call FortisBC regardless. Gas smell can travel through ductwork and wall cavities, so where you notice it isn't a reliable way to judge where the actual source is.
Most calls turn out to be something minor, like startup dust or a fitting that's loose but not actively leaking, but there's no way to tell which one you have by smell alone, which is why the same first steps apply every single time.
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