When heaters that have laid dormant over the hot summer months are finally turned on as the cold winter months roll in, it is not uncommon for the first use to smell like something is burning. This is typically just due to accumulating dust that builds up over time and usually is not a big issue. That being said, sometimes there is something else that could be prompting the burning smell so it is good to know when to take notice so you can react appropriately. If the smell of burning does not improve or disappear quickly, it may be the result of something else problematic which should be inspected by a professional HVAC technician. 

Is it Normal for Heater to Smell Like Burning?

We naturally react to the smell of smoke with urgency and concern due to what that smell could possibly implicate. When a heater is first turned on and results in a burning smell coming from the heat exhaust, it is usually just some dust that has built up while the heater was not in use. This smell should be faint and usually dissipates within the hour as the dust burns off. If the smell continues for an extended period, gets increasingly worse, is followed by smoke, or it smells like plastic is burning, these are all indicators that it is more than just dust. In these instances, the heater should be turned off immediately and professional help should be enlisted to identify and repair the problem. 

How Long Has It Been Since the Heater Was Turned On?

The burning smell that comes from a heater is typical when a heater has remained off for a season. That means that if the heater smells like burning on its first time running, it is usually just the smell of burning dust that has build up on the heat exchanger, ducts, or ignition system. This can also be exacerbated by a dirty filter which can release dust or mold that burns as it passes through the heater. 

Common Causes of Burning Smells Coming from Heaters

There are several common causes that can cause a burning smell when your heater is turned on:

1.     Dust on the Furnace

For seasonal use heaters, dust can build up when the heater is not in use. If the smell of burning starts to fade after a short period, then it usually means that dust is the culprit and will eventually burn off. If you notice a burning smell, check the furnace to see if there is dust build up. This is normal and no action is required unless the smell gets worse or is followed by smoke. In this instance, turn off your heater immediately.

2.     Dirty Furnace Filters

Poorly maintained filters will have too much build up to work effectively. This can lead to the machine working too hard, the integrity of the filter failing, or a build up of mold or milder. Each of these can cause a burning smell due to a burnt-out fan motor to additional dust buildup burning off. If the burning smell doesn’t dissipate quickly, then turn off the heater and check the filter. If the filter is dirty, replace it before running the heater again. If the new filter does not improve the situation, then there is likely another problem that may require professional help.

3.     Overheated Blower Motor

If the filter is completely blocked or the ductwork is pinched, your motor is much more likely to overheat from unnecessary strain. The lack of proper ventilation can also cause the moving mechanical parts to overheat which can result in safety measure that shut off your furnace. If your motor is running extremely hot, it may be time to consult with professionals to determine what needs to be done.

4.     Burning Oil

This only applies to oil furnaces. This can be caused by an oil filter that needs to be replaced. Burning oil can be caused by a leak as well so if there is thick smoke or a distinct burning odor that is coming from your heater, be sure to turn it off and call an HVAC professional to help identify and fix the problem.

5.     Damaged Furnace in Need of Repair

The smell could also be caused by a heating unit that is failing and has parts that have come loose. This could apply to mechanisms as well as wiring and generally need professional help to determine if the system can be fixed or needs to be replaced. 

Why Does My Heater Smell Like Burning Plastic?

Debris Trapped in Heating System

The heat coming out of the furnace can be hot enough to cause debris to release the smell of burning plastic if the heater is left on long enough. The same principles behind a convection oven would push hot air over a piece of debris before pushing the air into a room. This could be caused by a plastic piece of the HVAC system coming loose or some other random piece of plastic debris that somehow ended up in the ductwork. If this happens, it is usually localized to a room so check the vents and ductwork leading to that room to find the piece of debris. If possible, remove the vent and try and identify and remove the stuck piece of debris. If it can’t be located or removed, professional help will provide the necessary support to remove the debris. 

Wiring

If the smell of burning plastic is not localized to one room and is causing the entire home to smell like burning plastic, this is usually caused by an electrical issue. This could indicate that there is wiring that is short circuiting and potentially melting the wire covering or electrical housing. If this is the case, turn off the heater immediately and call a professional to inspect your heater. 

How to Prevent Burning Smell from Heater

The best way to ensure that your heater functions as expected without any instances of burning smells is to have it properly maintained by an HVAC professional. GS Home Services would be able to perform a check up of all important mechanical parts as well as clean up dust build up to prevent heater burn out and failure. Our team will also ensure that air filters are clean and replaced when needed to maintain clean smelling air.

When to Contact a HVAC Professional

Anytime the smell of burning persist or gets worse, it is time to call a professional. Do not risk causing additional damage by allowing a heater to run for long periods while smelling like they are burning. This increases the likelihood of significant burning hazards. Anytime a heater passes air that doesn’t smell like fresh air, it may be time to schedule a general check up of your heater to ensure that there are no major problems contributing to poor heater performance. GS Home Services has a team of licensed and trained heater and furnace professionals who understand how to inspect heaters to identify problems and fix them. 

Burning Heater FAQs