If your furnace smells strange or even stinky, don’t tell yourself that it’s just a figment of your imagination. Don’t ever ignore it, either. While furnaces normally do a great job of keeping residents cozy during our long, hard winters, occasionally they develop problems… and a peculiar odour could be the first sign of trouble!

Let’s take a look at various types of strange furnace smells, where these common furnace issues come from, and when they warrant contacting a furnace professional for repair or a furnace installation.

Burning Smell
Scary though it may seem, a burning smell is quite common when you first start up your furnace in the fall. The odour is usually caused by several months’ worth of dust. Normally this dust burns off harmlessly within a few hours. However, if the smell does not disappear after 24 hours or is accompanied by smoke, your furnace could have a more serious problem.

New Furnace Smell
Not quite as delightful as the “new car smell,” a newly installed furnace may give off an unpleasant odour when you use it for the first time. Don’t worry about it, though. This stems from the protective oil coating on your new heat exchanger, which will burn off in short order.

Smokiness
Furnace smoke, in the form of either a noticeable smell or a trigger to your smoke alarm, is bad news. It tends to signal that the furnace or its chimney is blocked, so that smoke cannot escape from your house. Turn off your furnace with the shutoff valve and close your gas supply line. Then call in a professional to repair the problem.

Hot Plastic, Rubber, or Metallic Smell
When you notice a scent of overheated metal, plastic, or rubber, that means one or more components of the furnace are in distress and you yourself are at risk, because the overheating could quickly lead to a house fire. Shut off your heating system and get in touch with a furnace repair professional, pronto.

Sewage Or Rotten Eggs
Hazard alert! The “perfume “ of rotten eggs or sewage comes from a substance that gas companies add to natural gas to make a gas leak readily detectable. When you smell this type of odour coming from your furnace, it is DANGEROUS to stay in your house. Go to a neighbor’s and contact an HVAC technician immediately. Do not re-enter your home until the tech gives you the all-clear.

Oily Aroma
An aroma of burning oil from your oil furnace means one of two things. First, the furnace filter might be clogged and need simple DIY cleaning or replacement (do this at least every three months during heating season – smell or no smell). If the odour persists, your furnace has an oil leak, which is a problem for a professional.

Musty Scent
Musty scents are an indication that mold or mildew is nearby. Here’s the question: Is the mold located in your air conditioner coil, which is right above the furnace? Or is it deep inside your heating and cooling air ducts? Get in touch with a furnace service company to clean up this problem. It’s not only smelly but downright dangerous for your indoor air quality – and your health.

Chemical Odour
When your furnace smells like formaldehyde or other chemicals – especially accompanied by a rattling furnace noise — you could be facing a cracked heat exchanger. This dangerous furnace failure can result in fire, in addition to leakage of poisonous carbon monoxide gas. Get everyone out of the house urgently before calling an HVAC service person.

Why Does My Furnace Smell Weird?