October 18, 2019

Why Do I Smell Gas or Burning from My Furnace?

And What to Do if it Lasts


Furnace smells like gas or burning


This is a question often asked during the Fall when homeowners are first turning on their furnaces to knock off that first chill in the air. Typically, this is a normal occurrence and no cause for alarm, but here is some information to educate yourself on the differences in odors and when you should call an HVAC furnace repair professional.

Different Types of Burning Smells from Furnace & Their Causes

Burning smell caused by dust

Heaters have sat dormant for months over the spring and summer. This off season causes a buildup of lots of dust in the unit – covering the inside, including the heat exchanger and burners. When your furnace turns on, this dust gets burnt off in the process. If your burning smell is caused by dust, it will go away within a few hours. If it does persist, make sure to check that the air filter is clean. If it is not, change the filter and give it another hour or so before checking back in on the odor.

Oil smell could be caused by dirty filter in oil furnace

Having a dirty filter can lead to some interesting smells, even an odor similar to oil. Make sure to check your filter before turning on your furnace for the first time.

Musty smell caused by dust or mold in air ducts

Air recirculates in your home multiple times per day. If there is dust or mold in the air ducts or mold in any part of the furnace, you may smell a musty odor. If you smell a musty smell, it is best to have a professional come check out your system and air ducts to make sure there is no mold present. They should also clean out the furnace if dust is found to be the underlying cause of the smell.

If mold is present in your air ducts, you can get an anti-microbial spray in your ductwork to remove the mold. If mold is present in the heating unit, call an HVAC service expert. If mold has completely overtaken the unit, replacement may be necessary.

Plastic smell

There are a couple main causes of a plastic smell coming from a furnace. The first is a foreign object in ductwork. This could be a child’s toy or a dog’s stuffed animal that you didn’t now made it into a vent. Pull off your vent covers and use a flashlight to see if any objects are visible.

The second root cause of a plastic smell from a furnace is an overheated motor or internal piece of the furnace that has overheated and burned. People sometimes describe this smell as “burning electrical parts” or even a gunpowder smell as well. If this is the cause of your smell, it needs to be fixed by a furnace repair professional.

What to do When You Smell Gas or Burning from Your Furnace

If you smell a burnt odor coming from your furnace, make sure to keep a close watch on it for 2-3 hours. Opening your windows before you turn on the unit for the first time will help to alleviate some of the odor also. Follow the steps included above, including checking the filter and vents depending on the type of smell. If the smell persists, you need to turn off the unit immediately and call a professional HVAC company to inspect the system and diagnose the problem. Frequently smelling gas could be a sign of a dangerous leak and needs to be remedied immediately.

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Annual Furnace Maintenance

Quality Comfort Heating & Cooling recommends having a professional HVAC company turn on your furnace for the first time during annual fall maintenance on the system. This way a service expert can help detect any abnormal smells and proactively fix any issues you may have while they are there for the tune-up. If you need to schedule a furnace repair or furnace maintenance in Cincinnati, OH, call Quality Comfort at 513-620-4822 or contact us online.