Does Your Furnace Smell? 5 Furnace Odors and What They Mean

Updated: Jan 12


While not all furnace odors are a sign for concern, there are a few that you should be aware of that would require immediate attention. No matter how strong the scent is, you should never ignore these as they often indicate unit damage or failure. To keep your family safe during heating season, take a look at the below list to understand the causes behind these smells.


1. Rotten Eggs Smell

Natural gas makes for a good fuel source for appliances throughout your home as it is highly flammable and combustible. Unfortunately, it can also be very dangerous when inhaled, causing dizziness, fatigue, nausea and breathing difficultly.


Believe it or not, natural gas is actually odorless. Most gas companies add scented chemicals as a safety precaution. These sulfur-based chemicals give off the distinct smell of rotten eggs so you can easily tell when natural gas is nearby.


If you have a propane or natural gas-powered system that smells like rotten eggs you may have a gas leak in your home. You should immediately contact a professional and exit your home until you know the area is safe again.


2. Diesel or Burning Oil Smell

Your furnace could create a smoky or burning oil smell for a variety of reasons:


  • If you recently filled your oil tank, any spillage may give off an odor as it dissipates. A couple of days should be enough for the faint odor to go away. If you notice it continues to linger, you may have an oil leak.

  • The smell of oil can be a symptom of a blocked oil furnace filter, causing the system to have to work harder. Be sure to replace your air filters regularly to ensure maximum efficiency.

  • If you keep your furnace in a basement or storage area, nearby items (such as toys, decorations, and clothing) could fall too close to the pilot light. These items could catch fire or melt, resulting in the smell of smoke and burning plastic.


Not sure why your furnace smells of burning oil? Let us help pinpoint the problem for you.


3. Electrical Burning Smell

An electrical burning odor could indicate an overheated blower motor in your furnace or heater. Under normal operating conditions the furnace should shut itself off if it begins to overheat. But if there’s something wrong with this safety feature, your furnace may continue to operate even as the motor works overtime and becomes dangerously hot.


The heat is often enough to melt away wire insulation, and soon your unit could produce electrical shorts and sparks that emit the smell.

If left untended, these sparks and melting wires create enough heat to start a fire in your home. If you smell electrical burning, cut the power to your unit and contact a qualified HVAC company for assistance.


4. Burning Dust Smell

Your system may smell of burning dust or must when you first fire it up for the heating season. This smell is a normal function of your system and should go away within several days of use. This occurs when dust collects on your unit and in your air ducts during the off season. If you notice the smell continues after a few days try replacing your air filter.


5. Chemical Smell

Chemical smells are not a natural byproduct of a correctly operating furnace and they need to be addressed immediately. These smells may happen for a few reasons, including a cracked heat exchanger. The heat exchanger component works by cycling heat out of the combustion chamber and then into the plenum. If this component is broken, it drastically increases the risk of fire. It may also distribute carbon monoxide fumes throughout your house.


Although carbon monoxide doesn’t have a smell, which is dangerous, any chemical smell is an indication of a serious problem and you should contact an HVAC company immediately.



Call Key Heating & Cooling and have our team inspect your furnace.


These smells, or any abnormal smell coming from your furnace could be a sign of a damaged or failing system.


Contact us today at 603-436-8811 or request service here.

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