What's That Smell? Why Your Old Furnace May Have A New Odor

If you've been using your heater for a while and have suddenly started smelling something like smoke when the heater comes on, you're right to pay attention. However, don't get too alarmed if the only symptom is an odor. It's common for heaters to emit a burning smell when first turned on after being off all summer, but it's also not unusual to smell a burning smell later on in the season. The keys to identifying the smell lie in the temperature outside and how long it's been since you cleaned the vents.

Heat Strips and Dropping Temperatures

If your furnace and heating system are electric, you may be dealing with some heat strips waking up if the temperature outside has dropped. The more your heater needs to work and the warmer it needs to get, the more heat strips it will use. If it's unusually cold out or you've increased the temperature on the thermostat, and the heater is now heating up strips that haven't been used in a while, you could just be burning off a lot of dust. The burning smell should go away relatively quickly, depending on how much dust you're dealing with. If the temperature keeps dropping, you may continue to smell the burning smell as yet more heat strips are brought into play.

Dusty Vents and Ducts

If it's been a while since your vents and ducts were last cleaned, that could be another issue. The dust in the vents isn't necessarily burning, but the odor from previous heater uses could be stuck in the dust in the vent. Check around the vent openings and clean away what dust you can, but have professionals do any deep cleaning in the ducts, rather than trying to get in there yourself. Not only do you risk injury, but you also risk sending dust spilling out into your home as you try to remove it from the ducts.

When You Should Be Alarmed

Of course, if you start seeing smoke come out of the vents, or your home seems a bit hazier when the heater is on, then you need to turn off the heater and have it inspected and repaired immediately. You should not actually be seeing anything coming out of the heater, even if the cause is just dust. (That's too much dust if you're seeing it fly out of the vents!) If you hear any strange sounds when the heater is on, or if the burning smell gets worse or persists, these are also reasons to get the heater checked out by a furnace repair specialist.

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