Most homeowners understand that they should contact their local HVAC company if they see a water leak or hear a strange noise coming from their equipment. But, some people may not know that odd smells are another cause for concern. In this article, we will look at some of these strange odors and their causes.

The Stench of Rotten Eggs

This particular odor will be very hard to miss; it’s a distinct smell that warns the resident that something is wrong. This odor is intentional; it’s added to your gas supply by the gas company to notify the occupants that there is a gas leak. If anyone in your home can smell a rotten egg smell coming from the heating system, it’s serious. First, shut off every gas appliance, then open up the doors and windows and move everyone outside. Then call a certified heating company to send out a technician to locate and fix the gas leak quickly.

A Burning or Electrical Smell

If you can smell a burning or electrical smell coming from your heating system, there could be a number of causes. Any of them are a cause for concern, and any situation where burning is occurring can escalate quickly. This is often a sign that your furnace is overheating or there may be a wiring issue that needs to be fixed. Shut off the heating and call your local furnace company and get them to send a technician to diagnose and fix the problem.

A Moldy or Musty Odor

The heating and cooling system in your home works together to keep you comfortable indoors throughout the entire year. The air conditioning part of your system can cause a buildup of moisture that could produce mold in your ductwork. This will create a moldy or musty odor that will be distributed throughout your home via the ducts. The odor is bad enough, but what you’re really smelling is mold spores, and everyone that can smell it, is breathing it at the same time. This is bad for your health and those with asthma, allergies or respiratory illnesses may be especially at risk. If you can smell mold contact your local HVAC company and ask them to carry out an indoor air quality analysis. They will then be able to give you a recommendation on how to get rid of the mold problem and improve your indoor air quality.

A Dirty Locker Room Smell

This may seem like a smell that you could never imagine coming from your furnace. These types of odors are usually caused by a buildup of bacteria in your heating system coils. During Spring and Fall, the heating coils cool along with the temperature outdoors, and then they heat up when you turn up your thermostat. The constant cycling between cold and warmth will result in a buildup of condensation. This moist environment provides an ideal breeding ground for bacterial growth. The only way to get rid of this smell is to clean out the system with a non-acid coil cleaner. Then you will need to change the air filter and test that the smell has gone. If the locker room odor persists, you will need to have the heating coils and air ducts thoroughly cleaned by a certified HVAC technician.

A Burning Oil or Diesel Fuel Odor

The furnace could be producing a burning oil or smoky diesel fume odor for three main reasons:

  • A furnace in a basement could have nearby items, such as plastic toys, boxes of Christmas decorations for outdoor furniture, stored too close to the pilot lights. These items can easily melt or even catch fire, and this could be producing the burning or smoky odor.
  • If you have an oil tank and when you last filled it there was some spillage, this could produce a fuel odor until it fully dissipates. This smell will typically fade after a couple of days, but if it persists, there could be an oil leak in your tank.
  • If you have an oil furnace, the unit may not be igniting all of the oil that’s passing through its burner. The waste oil can create a fog that has a similar smell to a diesel engine. This is dangerous, the mist is flammable and if it ignites it could cause a fire and produce excessive quantities of smoke.

If you notice any of these fuel or burning smells, contact your local heating specialist for expert help and advice.

4 Common Causes of Furnace Smells

Now that we’ve looked at the major sources of odd furnace related odors, let’s look at four more common causes.

  1. Damp Conditions

If your furnace is located in a damp part of your home, moisture can settle on the unit and when the furnace is turned on it will burn off. This could create a damp smell in your home, but it should quickly dissipate as the furnace continues to run.

  1. Cracked Parts

A good furnace will last for far longer than many of the components used inside. A prime example would be the heat exchanger, this component can crack, and this can release a chemical odor that smells a little like formaldehyde. If you notice this smell call your local heating company to examine your heating system. A cracked heat exchanger will release dangerous carbon monoxide in your home, and it can even cause fires.

  1. A Contaminated Air Intake

Many furnaces take in air from outside the home, anything in proximity to the air intake system can change the air characteristics of the heated air, and this includes odors. So, if your air intake is located near a sewer system opening, your heated air may smell like sewage.

  1. Dusty Equipment

When your furnace is not in use, dust can gather in and around the unit over time. When you begin to use the furnace again, the furnace will heat up and burn the accumulated dust. This will create a dusty burning smell for a short time and then it will dissipate. This can be avoided by cleaning the dust off the furnace before you start to use it again.