Why Your Furnace Smells and What It Means

While it is still hot here in Florida, soon, you will want to turn on the heat for those chilly Fall mornings and evenings. Does your furnace emanate a smell when you turn it on?

Your furnace is an important aspect of your year-round comfort, so if your furnace smells, here is what it could mean.

Why Does My Furnace Smell?

What you may not know is that your furnace runs during both summer and winter—in the winter it heats your home, and in the summer, it helps distribute the cold air using the same fan blower.

There are a few different reasons why your furnace may create an odor and knowing what causes the smell will help ensure that your furnace is running efficiently year-round.

Related> How Often Should My Heater Be Inspected?

What Kinds of Odors Can a Furnace Produce?

Here are some of the most common odors that you may smell coming from your furnace.

The smell of electrical wiring or plastic burning
Metallic smell
Burning dust or smoke
Rotten Eggs
Mold or mildew
Pet odors

Keep in mind, some of these smells are not caused directly by a problem with your furnace, but they may indicate an issue that can be fixed by an HVAC technician.

Burning or Metallic Smell

When you smell a burning or metallic smell emitting from your furnace, take caution. Burning smells can be a sign that the wiring has gotten too hot, or your fan motor is burning out.

A metallic odor can be a sign that an internal component of your furnace is overheating or rubbing against another part.

If you detect any metallic or burning smells, shut off your furnace right away and call Super Heat & Air for an inspection.

Rotten Eggs

If you turn on your furnace and smell a rotten egg odor, you may have a gas leak. Natural gas does not have an odor in its normal state, so gas companies add a safe, non-toxic odorant called mercaptan to the gas to alert you of a gas leak. Hence the rotten egg smell.

Natural gas is highly volatile and can ignite and cause an explosion in your home, harming or killing occupants. If you ever smell rotten eggs, turn off your furnace and call your gas company immediately.

This is a furnace issue that should be handled with urgency.

Burning Dust

The smell of burning dust is a normal smell and one that you will usually smell when you turn the heat function on for the first time of the year.

During the summertime, dust builds up on the heat exchange and the blower and when the burners are turned on for cold weather, the dust burns off and causes a burning dust smell to emit from the ducts.

The dust-burning smell will generally go away after the first few hours of use, but if it doesn’t, check the air filter to ensure that it is clean. If the smell continues to linger, call a technician from Super Heat & Air for an inspection and duct cleaning.

Pet Smells

Sometimes, the smell of pet hair will seem to emanate from the furnace registers. If you get a strong whiff of pet hair when you turn on the furnace, inspect the floor-level ventilator registers. There could be trapped dander and hair near the vent that is being drawn into the ductwork and causing the smell. Cleaning this will generally fix the smell.


If you notice the smell of sewage coming from your vents when the heater is running, there may be an open sewer or wastewater line located near your HVAC system. A quick inspection of external furnace vents can help you to identify the source of the sewage smell. You may have to call in a plumber to help resolve this issue.

Moldy Smells

If you smell musty or moldy smells coming from the furnace registers, it could indicate a possible mold infestation inside the ductwork of your home. Do not take mold infestation lightly. Mold can drastically degrade the quality of your indoor air and cause a host of health problems for those who live in your home.

Our licensed technicians at Super Heat & Air can clean your ducts and ensure that the air that your family breathes is clean and clear from contaminants.

MORE: Things to Check Before You Turn on the Heat

Furnace Maintenance and Repair

As you can see, some furnace smells are easily taken care of or will resolve on their own, while others need to be inspected and repaired by a licensed technician.

If you smell any metallic, burning, rotten egg, or moldy smells emanating from your furnace registers when you turn on the heat this season, call our pros at Super Heat & Air!

Superheroes don’t take a day off. We are available for 24/7 repairs and maintenance. Call us to schedule an appointment today (813) 279-8213

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