Flip a switch to heat the house. Smell something burning. Is the house on fire? It could be, but the real source of the smell is probably your furnace. Different types of furnaces create different burning smells, and some burning smells have related causes.
The Oil Furnace
Perhaps one of the smellier burning smells where furnaces are concerned, the oil furnace does smell like something’s burning because that’s what it does. The oil pumped into this furnace is ignited and burns continuously to create heat. There’s always a burnt oil smell lingering in the air, but it’s at its strongest when you first turn on the furnace in fall. Be sure to bleed the oil line so that there aren’t any hiccups in fuel flow. The hiccups in fuel flow can create short bursts of burnt smell.
The Propane or Natural Gas Furnace
Like the oil furnace, these types of furnaces have to burn something to create heat. You won’t smell the propane one as much as the natural gas, but the initial odor is still there. The natural gas one will initially smell like rotten eggs until the fuel begins to burn at a steady rate. If the rotten egg smell persists, contact an HVAC contractor. Too much of that smell indicates that the furnace needs repair.
The Electric Furnace
Electric furnaces come with a battery of smells. Sometimes it smells like burnt hair, which is a bit of lint near the ignition site or in the duct. Sometimes the smell is a little bit like burning copper or burnt metal. That usually means that metal components are heating up and/or they might be too hot and melting down. Watch to see if the smell dissipates over time.
A dirty furnace filter can also create a burning smell. Replace the furnace filter with a clean one before you start the furnace and that should help. Have a professional ventilation cleaner clear out the vents and ducts to reduce odors too.