A furnace burning smell that fades within an hour of the first fall start-up is usually just dust. But if the smell lingers for more than a day, keeps coming back, or gets stronger, something else is going on. Common causes include a clogged filter, debris near the burners, an overheating motor or worn electrical parts. This guide from Purcell Heating & Air helps Calgary homeowners figure out what's behind a lingering smell, which simple checks to try first, and when it's time to call a licensed technician.