A burning smell coming from your furnace can be quite a worrying experience. However, it isn't always necessarily a cause for alarm. Figuring out the reason your furnace smells like burnt rubber or some other substance can help you decide what to do to fix it and whether you need to call in a professional to do so.
Burning Dust and Debris
One cause of a burning smell coming from your furnace is simply surface-level dirt. If you haven't turned on your furnace for a while (such as over the summer months), there's a good chance there could be a buildup of dust and debris. Dust can settle anywhere on your furnace, from the burners to the heat exchanger, and once heat is reintroduced, it will quickly burn off.
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This type of burning smell should dissipate on its own fairly quickly, and it can be minimized by thoroughly cleaning your furnace before switching it back on after the summer. It may also be worth replacing your air filter, as excess dirt on your filter can also produce a burning smell.
Burnt Plastic Smells
If the smell emanating from your furnace is akin to burning plastic or rubber, it could be that a foreign object has become lodged in your heating unit and has started to melt. The smell could also indicate that a part of your furnace, like the fan belt or a plastic-coated wire, has begun to break down in the heat. If you notice this type of burning smell, it's best to turn off your furnace immediately and contact a professional to investigate it.
Electrical Burning Odors
It's possible for your home furnace to begin to give off a metallic or burnt-rubber odor if there's been an electrical failure and your furnace is overheating. Furnaces are usually programmed to switch themselves off if they begin to overheat, but a burning smell can indicate that this safety feature has been compromised. This puts your furnace at risk of an electrical fire and could be a sign of imminent danger. This type of smell is an indication that you should switch off your furnace and call in a professional who can check for problems and fix what's wrong.
Oily, Smoky Smells
If you have an oil-burning furnace, you may notice a smoky, oily smell that can come from a malfunctioning oil furnace. If you're noticing the scent and know that your furnace burns oil, you should first check the oil filter. It likely needs changing, as an older filter may be plugged, causing misfires and puff backs which can give a strong, oily smell. If changing the oil filter doesn't stop the smell, switch off your furnace and call in a professional.
A Smell of Gunpowder
It's also possible that a furnace can give off a distinct gunpowder scent. This is usually a sign that the circuit board or fan heater has burned out and is no longer functioning. This should be investigated by a professional. Stop running your furnace immediately and don't restart it until it's been fully checked.
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