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Odours Your Furnace Can Produce and What They Indicate

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A furnace is absolutely necessary for any home heating system, mainly because it will be utilized extensively during the winter months. While it generates heat, it might malfunction from time to time. One example is when it emits odours that it shouldn’t.

There are several reasons why a furnace may emit unusual odours. Sometimes, the smell is merely caused by the home’s heating system. It’s usually the consequence of a furnace problem that has to be rectified. Regardless, it should not emit odours and should be repaired as soon as possible.

This article discusses some of the most prevalent scents a furnace should not emit and how to remedy them. 

Smoke from a Failed Motor

If the smoke comes from your furnace, you will almost certainly be able to identify it. A smoky odour is not something you should be seeking from a furnace.

Depending on the origin of the smoke, cleaning the filters and ensuring that all soot is cleared from the gas burner, flame tube, and heat exchanger may be simple solutions. If the reason for the smoke is a faulty motor, you should get it repaired by a specialist.

Burning Dust Odours from Overheating

Furnace overheating is frequently the cause of an odour that smells like burning dust. This might be due to a malfunctioning motor or a blocked filter.

The simplest solution is to get the air filter cleaned. It would be best if you still inspected your furnace to verify that no dust is being drawn into it.

The Smell of Rotten Eggs from Your Gas Burner

Fumes emitted by the gas burner mainly cause the stench of rotting eggs. This scent is typical after turning off the gas valve, although it should not be an issue in the first place.

The odour can be eliminated by inspecting the gas valve and burner assembly. If the condition persists, you should seek expert assistance.

Foul Sewage from a Blocked Drain Line

Various circumstances might cause a nasty sewage stench or anything similar. It can occur due to a clogged drain line, a pump malfunction, a broken gas safety shutoff, a clogged filter, and other factors.

In most situations, cleaning the drain pipe will eliminate the odour. If, on the other hand, the stench remains and the case is not as simple as a clogged drain, you should contact a specialist to resolve the issue.

Mould in the Vents

Mould is a serious issue that must be treated immediately. One of the first symptoms of mould growth is the odour it emits. Even if you can’t see the mould, it’s a good idea to have a professional examine the heating system to ensure no mould is forming.

Mould might form on the vent or in the ductwork. The fungus can grow due to the heating system being kept in an overly damp environment. To avoid mould formation, make sure the environment is dry.

Metallic Smells from a Bad Motor

If your furnace emits a metallic odour, there is most certainly an issue with the engine. A faulty motor might cause this issue. If it isn’t, it might be the result of something else.

The issue with a defective motor is that it might overheat and burn out. A refrigerant leak can cause this. The burning refrigerant might provide a burning odour. In this scenario, it is advised that you contact a specialist to resolve the issue for you.


There are a few smells that can indicate problems with your furnace. A burning smell could mean an oil or gas leak, while a musty smell could tell that the furnace is not venting correctly. If you notice any of these smells, it is essential to have your furnace checked by a professional as soon as possible to avoid further damage.

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