Why your furnace has a strange smell

The best way to make sure your furnace will do its job safely and efficiently all winter is to give it a checkup prior to the winter season. That way, any problems can be fixed and the components can be checked to make sure they are not getting ready to fail. If the furnace is working as it should, there should not be any smell noticed inside the house. If there is, you should have it checked out right away.

Gas or fuel

You should not smell anything coming from your furnace or through the ductwork that resembles the smell of fuel. Depending on what type of furnace you have, fuel oil or natural gas is likely to be what it burns to generate heat. Gas companies will put an ingredient in the gas to give it an unpleasant odor that smells similar to rotten eggs. Otherwise, there would be no odor at all. Gas companies give it this odor to make it possible to detect a leak. Therefore, if you smell it, the gas is either passing through the furnace in its raw state or there is a leak in the supply lines somewhere. If you smell raw gas, you should call for help immediately.

Many furnaces use oil as fuel. This oil is usually the same thing as diesel fuel, so if you smell it, you have a leak somewhere. Just like with a gas leak, you should call your furnace repair professionals right away if you smell raw fuel.


You should not smell anything that smells like burnt fuel or exhaust fumes either. The presence of an odor like this means the furnace is not operating efficiently. By the same token, you should not see any smoke coming from it. Smoke is a sign of incomplete combustion. Therefore the presence of smoke or an exhaust-like odor means your furnace needs a tune up. Keep in mind that carbon monoxide could be present as well. While carbon monoxide has no smell of its own, any other odor could be an indication that it may be present. You might want to check the reading on your carbon monoxide detector just to be sure.

Burnt Wiring

If you smell something that has an odor like burnt rubber, it may be coming from the wiring. This would be an indication of an electrical problem somewhere. Something may have shorted out or overheated causing wiring or electrical components to burn. If you smell this, you should the power to your unit off and call for repairs.

Musty Odors

A musty smell may indicate the presence of some moisture in the ductwork. The presence of moisture means conditions are right for the growth of mold. Keep in mind that your summer air conditioning unit is likely to be tied in with your heat source. As a result, condensation from the air conditioner could have somehow contributed to the presence of the moisture.

In short, any strange or unusual smell coming from your furnace should be checked out. You should not be smelling anything from your heat source. If you do, your next phone call needs to be to your furnace repair people.


Categories: Heating & Cooling

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