Why Does My Furnace Smell? A NJ Tech Answers | Air Experts

Don’t worry—we’ll help you figure out what’s causing the problem.

In this blog, we’ll explain what causes the following furnace smells:

  • Burning (dusty) smell
  • Rotten eggs smell
  • Burning (fish-like) smell
  • Chemical smell

Scroll to the section that best describes your odor for more information about what causes it and how to eliminate it.

Want an NJ pro to fix your furnace? Our trained technicians can quickly find what’s causing the smell and fix the problem.

Smell #1: Burning (dusty) odor

One of the most common furnace smells is a dusty, burning odor. Most people notice this smell when they turn on the furnace for the first time during the cooling season.

The good news? This smell usually isn’t any cause for concern, as it just means dirt has settled on your furnace over the summer and is simply burning away.

That said, if the smell persists longer than a week or so, then you should contact a heating specialist to inspect the furnace and clean it if necessary. 

Smell #2: Rotten eggs odor

Smell a strong, rotten eggs odor coming from your furnace? If so, that’s usually a surefire sign of a gas leak. 

You see, many furnaces in our area use natural gas as a fuel source for heating systems. Natural gas is odorless; however, gas suppliers add a chemical called mercaptan to give the gas a detectable odor to alert people of a gas leak. Since leaking natural gas can lead to an explosion or breathing problems, this rotten egg odor (while unpleasant) can be a lifesaver. 

Normally, natural gas is safely transported into your furnace via enclosed gas lines. However, if one of the gas lines isn’t tightly connected or has formed a leak, then natural gas can escape from its intended path and fill the air surrounding the furnace.

If you notice this smell, you should immediately contact a professional for assistance. An HVAC technician can quickly find the source of the gas leak and repair to keep your home safe. 

Smell #3: Burning (fish-like) odor

A burning, metallic or fish-like smell is a sign of an electrical problem with your furnace. The electrical issue could be anything from an overworked or failing motor to frayed electrical wires in the system.

Needless to say, if you notice this electrical smell, you’ll want to contact a professional for assistance ASAP. Electrical problems can lead to serious damage to important components or even lead to an electrical fire.  

Smell #4: Chemical odor

A strange, chemical smell (similar to formaldehyde) suggests a leak or crack in the heat exchanger. 

We’ll explain: The heat exchanger is the part that’s responsible for heating your home’s air. It consists of a series of metal coils and is located in the heart of the furnace. If the temperature inside the heat exchanger gets too hot, the metal coils can form cracks, which allows fumes and gases to escape into the air surrounding the furnace. Often, these gases have an odd chemical scent.

If you notice this chemical odor around your furnace, contact a furnace professional for assistance. A cracked heat exchanger is a potential health hazard, so it should be replaced or repaired immediately. 

For more information about what to do if you have a cracked heat exchanger, refer to our blog, “How Much Does it Cost to Replace a Heat Exchanger in New Jersey?” 

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