Not every furnace burning smell is cause for alarm, but some are. Calgary homeowners can use this quick guide to sort the harmless from the dangerous. A faint dust smell that fades within an hour is normal. A smell of hot plastic, melting wires or burning rubber means something is overheating, and you should turn the furnace off right away. Smoke, or a smell that keeps getting stronger, is never normal. Purcell Heating & Air explains the warning signs and when to call for 24/7 furnace repair.