What to Ask a Customer Whose Furnace Smells Like Burning Before Sending a Tech

First, the safety questions

• Is there smoke, or can anyone see flames or sparks? If yes: everyone out and call 911.
• Does anyone smell gas, like rotten eggs? If yes: everyone out, do not flip switches, and call 911 or the gas utility from outside.
• Has a carbon monoxide alarm gone off, or does anyone have a headache, dizziness or nausea that gets better outside? If yes: everyone out, and call 911.
• Does it smell electrical, like hot wires or melting plastic? If yes: turn the furnace off at the thermostat and at the furnace switch or breaker, and leave it off until the tech arrives.
• Is anyone in the home very young, elderly or unwell, and will the house get cold with the furnace off? That call moves up the schedule.

Narrowing it down: the quick checks

• Is this the first time the heat has run this season? A dusty burning smell in the first hour is often dust burning off, and it should fade.
• How long has the smell been going? If it has been more than a few hours, or it comes back every time the heat runs, it is not just dust.
• What does it smell like: dusty, electrical, rubber or plastic, oily, or like something cooking? Their own words help the tech.
• Is the smell strongest at the furnace, at one vent, or through the whole house? One vent can mean something fell in or is sitting on it.
• Is anything stored against the furnace or on top of it, like boxes, laundry, paint cans or a space heater nearby? Moving it away is safe to do.
• When was the filter last changed? A clogged filter makes the furnace run hot, and a new one is safe to put in.
• Is anything sitting on or right next to a floor vent, like a rug, a toy or a curtain? Pulling it clear is safe to do.
• Is there a blinking light visible through the small window on the furnace door? A count of the blinks helps the tech. Do not open the panel to see it.

What the tech needs to know

• Gas furnace, oil, electric, or a heat pump, and the brand if they can read it.
• The age of the system, or a photo of the label so the tech can read the model and serial number.
• The smell in the customer's words, where it is strongest, and whether it was fading or getting stronger.
• Whether the furnace is off now, and whether it was turned off at the thermostat, the switch or the breaker.
• Any blink code they could see, any error on the thermostat, and any noise that started with the smell, like squealing or grinding.
• Where the furnace is: basement, attic, closet, crawlspace, garage, and whether it is easy to reach.

How it sounds on the phone

The three ways this goes wrong

• Calling every burning smell normal. Dust burning off fades; an electrical or plastic smell, or one that keeps coming back, is a reason to turn the furnace off and send a tech.
• Skipping smoke, gas and carbon monoxide because the customer said burning, not gas. Those questions come first, every time.
• Not asking what the smell is like and where it is strongest, so the tech arrives without the right part and the customer pays for a second visit.

A furnace that smells like burning is smoke, gas and carbon monoxide first, then what the smell is and whether it is fading, then the details. Ask in that order, and the family stays safe and the tech arrives ready to fix it on the first visit.