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Furnace Smells and Odours

Common Smells Not Likely to Present Danger

Burnt Dust

Late August, early September in Calgary usually signifies the time of year your furnace turns on for the first time since early spring. Because we live in a dry climate there can be a significant buildup of dust accumulating in your heating system. When the burners light, it will burn the dust and the blower moves the warm air through the ductwork.

The burning dust creates a familiar odour and will dissipate after just a few heating cycles.

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Musty, Humid Odour

It’s not uncommon for the furnace to give off a humid or musty smell at the beginning of each new heating season. This is particularly true if you have an HVAC system with air conditioning. Your cooling system may have a buildup of moisture, from running over the summer, and it can cause a familiar damp, musty odour. This smell should be eliminated after a few heating cycles have dried the moisture.

There could be an underlying issue if the smell lingers over a longer period of time. Call an HVAC professional to inspect the problem to avoid a serious repair later on. If left unattended it may allow mould and mildew to grow uninhibited within your HVAC system.

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Strange Stale, Organic Smell

A dirty furnace filter can create strange organic smells, unique to your home, and can be related to the smell of cooking, pets, dust and dirt. When a furnace filter becomes clogged or dirty it can be contaminated by different organic odours found within your home. The filter is preventing the necessary airflow needed to properly circulate clean, filtered air from the registers allowing stale smells to linger longer in any given room.

A telltale sign of a dirty furnace filter can include excessive dust around your home as can be seen on fan blades or a buildup of dust and dirt in and around the registers.

Changing your filter on a regular basis is important for an efficient heating system and it will also increase the lifespan of your furnace.

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Smells That May Indicate Danger or Unsafe Conditions

Chemical or Noxious Odours

When you smell chemical or noxious fumes (can be a sweet smell) – which would be a very uncommon odour you’ve experienced from the heating system, it may be the telltale sign of a cracked heat exchanger. This is a serious issue that requires immediate attention.

A cracked or damaged heat exchanger can circulate dangerous carbon monoxide fumes throughout your home as well as increasing the risk of fire. This is one of those times you need to call an HVAC professional to ensure the safety and wellbeing of the occupants in the home.

Rotten Egg Smell

Producers of natural gas, which is odourless when produced, add an obvious rotten egg smell to help quickly detect it when leaking into unwanted spaces or areas. You may smell a hint of natural gas upon your furnace burners being lit, however, if this smell lingers for any length of time – SHUT OFF the gas valve, ventilate the area, and call your natural gas supplier.

If you can confirm the smell is emanating from your furnace – SHUT OFF the gas valve, ventilate the area, and call an HVAC professional.

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Acrid, Metallic Odours

Generally speaking if you encounter metallic or acrid odours in or around your furnace it usually an indication that electrical wiring is or has been recently burned. Short circuits in electrical wires, or component parts causes overheating resulting in melting of the wire insulators protecting the electrical wire or the melting of a piece of a furnace part. It goes without saying this can create many other issues for your HVAC system including presenting a danger to you for electrical shock.

If you smell a metallic odour that you believe is related to electrical malfunction – SHUT THE FURNACE OFF and have an HVAC expert diagnose and repair the issue.

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Burned Plastic

Because plastic is integrated into the manufacture of many electrical and circuit boards it is at risk of melting or burning when overheated.

When you smell plastic from the furnace it is generally a signal that a component of the furnace has failed. SHUT THE FURNACE OFF and have an HVAC expert diagnose and repair the issue before there is major damage or the heating system shuts down completely.

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Strange Furnace Odours

Whenever you encounter a strange unidentifiable smell from the furnace that continues after several heating cycles it is wise to have your heating system diagnosed. Today’s furnaces are designed to run relatively problem-free as long as you follow the manufacturers recommendations.

When the furnace produces odours for any extended periods of time it is usually an indication something has failed within the heating system. Have your system inspected to correct the issue, if needed, and you will reduce the chances of an increased risk of safety as well as unnecessary expensive repairs, if left unattended.

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