SOLVED! Why Your Furnace Smells and What it Means

Now that the weather is getting cooler, you might find yourself getting ready to turn on the heat. But what happens if you smell an unexpected smell coming from your furnace when you turn the thermostat to “heat?”  


Wondering ‘what’s that smell’? No matter how strong the smell coming from your furnace, there are some scents that you should never ignore, as they can often indicate issues that need to be addressed or signal possible HVAC system failure: 


#1. Rotten Eggs or Sulfur 

#2. Dirty Locker Room or Socks 

#3. Electrical Burning 

#4. Diesel or Burning Oil 

#5. Dusty & Musty 


To ensure that your family stays safe when you turn on the heat, keep reading to learn more about the most common smells that might be coming from your furnace, what you can do, and when you should call in a professional! 



Smell #1. Rotten Eggs or Sulfur  


IMPORTANT: If you smell rotten eggs or sulfur, exit your home and call in a professional from Integrity Home Solutions immediately.  


Natural gas is a popular fuel source for home appliances because of its highly flammable nature. It is widely used in households for cooking, heating, and powering various appliances. However, the same properties that make natural gas an efficient fuel also make it dangerous if not handled properly. The inhalation of natural gas can be deadly and may cause dizziness, headaches, nausea, or even unconsciousness.

To mitigate this risk, many natural gas companies add mercaptan chemicals to their supply. This odorant gives off a strong smell similar to rotten eggs, making it easier for people to detect if there’s a leak in their home or business. It’s an effective safety precaution that has helped prevent countless accidents over the years.


If you have a propane or gas-powered furnace and you smell sulfur or rotten eggs, you may have a leak. It is important to take gas leaks VERY seriously and never try to pinpoint the gas leak on your own. Always call in a professional or the local gas company to ensure you don’t have a leak.  


Smell #2. Dirty Locker Room or Socks  


You may be familiar with that overwhelming smell of old cheese and old sweat coming from a locker room or a pile of your kid’s dirty socks, but you might not expect that to come from your furnace.  


That dirty sock smell occurs when bacteria build up on your heating system coils. How does this happen? Well, during the cooler seasons, the coils cool with the outdoor temperature fluctuations and reheat when you turn up the thermostat. This constant cycling between warm and cold can cause condensation to build and in turn creates the perfect moist environment for bacteria to grow.  


The best way to eliminate this foul smell is to give your system a good old-fashioned cleaning. You can start by replacing your unit’s air filter, and then call an HVAC technician from Integrity Home Solutions to come out and clean your furnace and air ducts to ensure that the smell doesn’t linger!  


Smell #3. Electrical Burning or Ozone  


If you have ever been outside during a thunderstorm in Tampa Bay, you’ve likely smelled the sharp smell of ozone, a scent that is faintly metallic. Your furnace might emit a similar electric or metallic smell if it overheats.  


As your furnace ages, components like bearings may cause the blower motor to seize up or bind and cause extra resistance inside your furnace. This adds additional voltage inside the motor resulting in excessive electrical heat which can melt wire insulation and produce electrical shorts or sparks that smell like ozone. 


Be warned—if left unfixed, these melting wires and sparks can create enough heat to start a fire in your home. If you smell even a hint of something electrical burning, cut the power to your furnace and call a heating technician from Integrity Home Solutions for help.  


Smell #4. Diesel or Burning Oil  


Your furnace may create a burning oil smell for many reasons including: 


  • If your furnace is in a storage area, nearby items like boxes, clothing, etc. might be too close to the pilot light and melt or catch on fire.  
  • If your furnace has a heating oil burner, the unit may not ignite all the oil as it passes through the flame. Instead, it may create a fog that smells like diesel fuel. If that fog ignites, it could result in a large explosion and heavy smoke.
  • If you spilled any oil when you filled the tank, it may give off a smell as it dissipates. This smell should fade after a couple of days but if it lingers you might have a leak.  


Not sure why you keep smelling burning oil? Call our team at Integrity Home Solutions at (813) 473-6007 and we will pinpoint the problem for you!  


Smell #5. Dusty & Musty  


This is a very common smell when you first turn on your furnace for the season. You may smell a damp, dusty, or musty smell. This smell occurs due to dust, dirt, or other debris that has been collected on the unit’s coils and in the air ducts. As your furnace warms, the dust and dirt burn away and smell faintly of burnt dust.  


This smell should go away after the first few uses of your furnace, but if it lingers, you might have a clogged air filter. Change your air filter and see if that makes a difference.  


Trust Your Nose, Call Our HVAC Pros 


Your nose is often your first clue to a broken or damaged HVAC, so if you smell #’s 1-4, don’t hesitate to call in our qualified technicians from Integrity Home Solutions for furnace repairs. HVAC odors often point to a bigger problem with your unit. We proudly serve all of Tampa Bay and are available for 24/7 emergency service calls.  


Meet your heating experts and keep your home performing at its best; call (813) 473-6007 or book an appointment online today!


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