Dangerous Furnace Smells You Should Never Ignore

Your furnace is designed to keep you safe and warm all winter long. But when problems arise, the quicker you handle the issue, the less chance you have of it turning into a major problem for you, your family, your health, or your heating equipment. Smells coming from your furnace should never be ignored since they could be signs of a serious or even dangerous problem. While it’s normal to notice a dusty burning smell the first time a furnace runs in the winter, if the odor continues, it should also be checked out by a professional.

Regular inspections and routine maintenance are a must for keeping your home furnace in safe and premium working condition. Any mechanical problems that arise requiring the attention of a professional furnace technician will often be first detected by unusual smells emanating from your furnace.


Rotten Egg Smell

The most obvious and serious odor you may notice from your furnace is the rotten egg smell that indicates a gas leak. Natural gas on its own has no taste or smell. Because of its deadly qualities, a rotten egg odor is added to the gas to make leaks easier for people to detect without equipment. A gas leak is a dangerous situation, so if you notice a rotten egg smell coming from your furnace, open windows to let in fresh air, evacuate the home, and call your local gas company and/or 911 to report the leak.

Burning Electrical Smell

Odors similar to an overheated iron or hot metal can be an indicator of broken or malfunctioning parts within your HVAC system.  If you smell that coming through your vents when the furnace is operating, it could be a sign your furnace blower motor is seizing up due to worn out parts. If not taken care of quickly, it can lead to overheating, excessive voltage, or even fire. If heat continues building within your furnace, it can cause wires to melt and produce further electrical hazards throughout your home. In the case of a burning electrical smell throughout the house, use your thermostat to shut off the furnace and then call a licensed HVAC technician to inspect the system.

Chemical Smell

A chemical odor like formaldehyde could be a sign of a cracked heat exchanger. The heat exchanger exists in your furnace and transfers heat from the combustion chamber into the furnace. If the heat exchanger is cracked, carbon monoxide fumes can be circulating through the equipment and can settle into your home’s ductwork. Carbon monoxide detectors should be installed on every level of a home, especially near the furnace, because the gas is odorless and colorless. If you notice a chemical smell coming from your furnace, call a professional to inspect the unit as soon as possible.

Dusty Burning Smell

At the beginning of heating season, it is common to smell burning dust or oil after the furnace is initially placed into service. Dust settles into the system and oil can seep onto components while the furnace is not in use. However, if the smell lingers, try changing the furnace filters. If that does not get rid of the dusty burning smell, it could indicate a serious problem. It could just be that your furnace needs a deeper cleaning, or there could be a more serious issue. Either way, shut off the system and contact a technician for an inspection right away.

Musty Furnace Odors

HVAC ductwork is a prime place for bacteria or mold to grow and present the danger of serious health problems. If you smell a musty, damp odor from the heating ducts it may indicate a problem with the system. Always be sure to have your heating system serviced and inspected regularly. If a professional cleaning does not eliminate the musty odor, the problem could be located in another part of the home.

Moldy Smells

A smell of mold coming from the furnace indicates a potential mold infestation inside the ductwork. You should never take mold infestation lightly as it can degrade the quality of indoor air and can cause serious respritory problems. It can cause people to suffer from flu-like symptoms, accompanied by sneezing and coughing. Through our duct cleaning service, the qualified furnace technicians at Aire-Tech will not only remove mold and mildew from the ducts but also take measures to ensure that it does not recur as well.


If you experience a smokey smell coming from your furnace, immediately turn the furnace off and open your windows. This may occur when the furnace chimney (also called a “flue pipe” or “exhaust vent”) is blocked. The furnace’s combustion exhaust has to go somewhere, so it is forced into the ductwork.

If the smell is faint then open a window to ventilate and call a professional to schedule a service. If the smell is sudden or strong, you may need to temporarily leave your home and wait for a professional to come and identify the source of the smoke.


Prepare Your Furnace for the Season

Preventive maintenance can eliminate many of the problems that cause strange odors before they have a chance to begin. Always perform the following maintenance tasks before lighting your furnace each season:

  • Check the flue and have any holes or worn piping repaired
  • Dust and rinse off all air vents in the home
  • Replace the air filter according to the manufacturer’s recommendations
  • Clean the furnace combustion chamber
  • Check to see that all belts are tight and in good condition

Do not risk your home and savings to a dangerous accident with your oil or gas furnace. Eliminate as many risks as possible by performing the above preventive maintenance and by having your furnace professionally cleaned and inspected before each heating season.


Final Thoughts

Abnormal smells coming from a furnace could be one of the signs of a failing or damaged system. No matter what type of furnace or heating system you have, never ignore furnace odors. In a vast majority of cases, they are a sign that something is not working the way it should.

If your system needs repair or inspection before winter, call us on 951-926-1002. You can also visit our Contact page and complete the contact form.