BlogHVAC ExplainedDecember 27, 2021Why does my heater smell like it’s burning?

It can be disconcerting to turn on the heat in your home for the first time in a while and not only smell something burning, but have the smoke alarm activate. This is not unusual, especially in a hot state like Florida, where there may be a significant gap since the last time the heater was used.

Not to worry, says, Alan Wilson, Millian Aire’s Vice President of Technology and Training — the burning smell is innocuous and can be expected. The scent comes from dust collecting on the unit and being heated then incinerated when the heat is turned back on.

“When AC units operate, they produce air that is saturated with water,” Wilson explains. “A little bit of that water will stick to that unit, and that moisture then attracts dust and dirt. As the liquid evaporates, the dust and debris are left behind, with more accumulating over time — even in a clean home — in a quantity that relates to the amount of time since the last time you turned on the heat.”

In Florida, it’s not uncommon for this small incineration to cause the smoke alarm to be activated. To avoid that stress (especially for elderly residents), Millian Aire offers a maintenance plan including a visit by a technician every six months to inspect and clean the HVAC system and turn on the heat. This not only circumvents the nuisance of a burning smell and alarm but keeps the system operating at peak efficiency.

Not Mold or Mildew

It’s also good to recognize that the burning smell doesn’t generally indicate a cleanliness issue in the home, nor does it imply the presence of mold or mildew.

“It’s just dust on the unit’s heating strip,” says Wilson. “That’s why that burning scent smells like smoke. It’s an electric heat problem and is only an issue in states like Florida. In this state, if you have a heat pump, you can conceivably go months in the winter before the electric heat ever turns on, and sometimes it never comes on the whole winter. So, there are times when you can get up to a year and a half worth of dust on the unit’s heating strip.”

There’s a common misplaced perception that the AC unit filters the air and keeps dust out. Even with filters in place, this is not really the case, says Wilson, adding that the AC system is not a vacuum purifying the air — it just circulates cooled or heated air.

Not a Fire Hazard

Smelling something burning when turning on the heat after a long period also doesn’t indicate a fire hazard. That’s because HVAC units are constructed of metal, with a flame rating. The same applies to your home’s duct work, which is made of fiberglass and considered non-flammable.

“It’s an inconvenience, not a danger,” Wilson adds.

The best solution is to have an HVAC technician keep the heating elements and coils clean as part of a maintenance plan. But at a minimum, turn on the heat every six months to help minimize the smell and the likelihood of a smoke alarm going off.

Feels Cool Instead of Hot?

Another phenomenon that can be experienced when turning on the heat for the first time in a while is feeling as if the unit is blowing cool air instead of warm, says Wilson. This is a common perception, based on the difference between the warmth of air inside the home compared to air from an electric heater.

This is caused by an electric heater producing air that’s 15-20 degrees warmer than the air inside the house, says Wilson. For example, if it’s 70 degrees in the home and you turn on the heat, the HVAC unit will produce 80-85-degree air. That air will be warm compared to the air in the house, but can feel cool in relation to the temperature of skin. This is just a perception issue, explains Wilson, and doesn’t indicate that the heat isn’t working properly.

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