Common Reasons Why Furnaces Give Off Strange Odors

Every time you turn on the furnace, you expect the unit to produce and distribute warm air throughout your home. What you might not expect is a strange odor that wafts in while the furnace is running. While heating systems sometimes give off unusual strong smells, some resolve independently. However, if that doesn't happen, you must consider furnace repair. 

Maybe there's a potentially dangerous problem with the heating unit that must be addressed right away. Knowing the possible causes of a scent will assist you to take the necessary measures to freshen the air. This blog shares common causes of strange furnace odors.


Whenever a furnace has any form of obstruction, you will notice a significant change in the air smell. The material causing the blockage will determine the resulting odors. For instance, if the chimney has an obstruction, it will cause the furnace to smell smoky. If pests get stuck and die, the furnace will give off a decaying smell. You will need to switch off the heating system and get an expert to inspect it and resolve any obstruction issues you face.

Oil Leak

If you use an oil-fired furnace, the system can give off unwanted odors occasionally. For instance, if some oil is spilled when refueling the furnace, the smell may linger for several days and clear out.

In other cases, oil-related odors occur due to a leak. You will need an HVAC technician to inspect the furnace for leaks and perform repairs. Also, an issue like inadequately burned oil caused by faulty or dirty burners can lead to the production of nauseating aromas.

Gas Leak

If your heating system operates with natural gas, propane, or LP gas, you may notice a slight gas odor once you open the fuel line. If you sense a rotten-egg smell lingering around, shut off the furnace and gas supply and ask your loved ones to leave the rooms with the gas odor. Your carbon monoxide detectors will help you identify the presence of the dangerous gas in all rooms.

Then call a technician to check for leaks on the gas lines or determine if the connections are properly fitted. In some cases, it might be challenging to identify the gas smell source on your own, so you will need the expertise of an HVAC technician to isolate the damage or leak. Repairs should be done immediately if there is a loose-fitting part or if the gas line is leaking.

Contact a professional if you have questions about furnace repair