What Does a Smelly Furnace Mean?

What Does a Smelly Furnace Mean?

Nov 27, 2014

Indoor air quality in your Orlando home can be affected by many things: pets, cooking odors, chemicals in upholstery and carpets, or even a smelly furnace. If you notice an odd smell when your furnace is working, a little detective work can help narrow the problem, making a service call more effective. 


At the beginning of heating season, you may detect a musty, dirty or damp smell. This can be from accumulated dust in the ductwork, but will quickly dissipate when your furnace cycles the indoor air through your clean furnace filter.

Another likely place for dust to build up is your furnace’s heat exchanger. A layer of dust settling on it, then suddenly ignited with the first firing of the season, can cause a smelly furnace odor like singed laundry. This thin layer will burn off quickly and does not require service.


Mold or mildew spores can get trapped in your old furnace filter. If your HVAC system has its own humidifier, check that air filter also. While you may have remembered to replace the A/C filter, last season’s furnace filter may have provided a six-month head start for mildew.

If your filters are not disposable, after you have cleaned them using your usual routine, rinse with water and vinegar to kill odors.


A strong electrical burning smell could be from foreign objects in the ductwork. Small children’s toys stuffed into registers are often the culprits. Without disassembling or damaging your ducts, see if you can uncover a partially melted bit of plastic toy.

A smelly furnace sending up electrical burning odor could mean an overheating furnace blower motor, or a cracked heat exchanger. The mildly annoying smell actually points to a dangerous problem needing immediate servicing.

Oil and Smoke

In an oil-fired furnace, an oily smell means the system’s oil filter could be clogged. Smoke could mean a blocked chimney, preventing harmful combustion fumes from escaping outside. Call your HVAC professional if you smell smoke when the system is firing.

For more guidance on solving a smelly furnace, contact us at Rinaldi’s Air Conditioning Service.

Our goal is to help educate our customers in Orlando, Florida and surrounding areas about energy and home comfort issues (specific to HVAC systems). For more information about furnace smells and other HVAC topics, download our free Home Comfort Resource guide.

Credit/Copyright Attribution: “Piotr-Marcinski/Shutterstock”