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Why does your furnace smell

Your furnace is supposed to keep your home comfortable and cozy during the winter season, but a nasty furnace smell can do just the opposite.

You may be wondering what that smell is and where it is coming from. The foul furnace smell must be somewhere in your furnace/duct system and is being circulated throughout the home by your furnace blower fan. The smell could be a variety of things and it is important to be able to distinguish between the dangerous smells and the ones that don’t do much harm.

Dangerous Furnace Smells

The smell of something burning or a strong dusty odour could indicate that there is something on fire. You should immediately check on your furnace and make sure that nothing is smoking or in flames. Your home’s smoke detector should do it’s job in detecting such an issue if it is in working condition, but it is best to check on your own to be certain. A dusty smell is common when turning on your furnace for the first time, but the smell should go away shortly. If the smell persists and does not go away then this could be a sign of it being necessary to clean out or replace your furnace’s air filter. If this does not solve your problem then the next step would be to call a service technician who will be able to help.

If what you are experiencing seems to be the smell of overheated metals or an electric smell, this is a sign that your furnace is too hot or that the airflow has become restricted and is not allowing for heat to escape the system. If this is the sort of furnace smell that you’re experiencing you should shut off the furnace immediately and contact an HVAC technician.

Another smell that is worth worrying about is the stench of rotten eggs. If you can smell the odour of rotten eggs coming from your ventilation system, this is most likely caused by a gas leak. Since natural gas is odourless, this rotten egg-like smell is added to it. In this case, you and everyone in the home should evacuate immediately, turn off the gas at the tank located outside, and make a call to a technician for further assistance. These precautions should also be taken when there is the smell of any other fuel in the home, such as oil.

Other Unpleasant Furnace Odours

The rest of the furnace smell listed below are not caused by the furnace itself, but rather by something that made its way into the system. Most of these smells can be stopped by just cleaning the ducts, but first you must find out what the root of the smell exactly is.

One of the most common of these scents and possibly the one you’ll be least thrilled to find the source of is the scent of small birds or rodents. These small and sneaky creatures often make an unwelcomed visit to the vents and attics of homes. This will lead to the putrid stench of a dead animal lingering through your ventilation system and the rest of your home. The first step would be to remove its remains from the system. Next you should clean out that area of the air ducts and then remove the smell from your home by leaving some doors and windows open to allow air flow.

If the terrible smell you are experiencing is from wastewater or sewage, the root of the scent may be in an open sewer line or broken black-water line somewhere close to an intake used by your furnace. Take a look around the external vents and your furnace to see if that’s the problem. This can be solved by calling a plumber to close off the sewer line.

It is no secret that your beloved house pet, whether it be a cat, dog, or anything in between, can leave some unwanted sights and smells throughout the home. The source of this smell may be from your pet’s urine, waste, or excess hair. If whenever your furnace is running you can sense the smell of pet urine or excrement, you  should look around near any floor level vents. This smell will be picked up if its source is near a vent. This problem is rather easy to solve, just clean up the mess and the smell is gone.


If you are in need of assistance with a furnace repair or are looking for a replacement in Ontario, DeMark Home Ontario is here to help. We provide quick and efficient furnace service and replacement performed by our highly trained and experienced technicians. Call us at 647-847-2998 or fill out online request form and we will be happy to assist you with your request.

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