Furnace runs but there is a burning dust or metallic smell when heat first comes on.

Safety: If you smell burning plastic, electrical, or see smoke, turn off power immediately and call a professional.

Steps:

• Initial burn-off: At the start of the heating season, a mild dusty smell for a few hours can be normal as dust burns off the heat exchanger. Open windows slightly to ventilate.
• Inspect for debris: With power off, remove the blower door and look for debris on the heat exchanger or in the blower compartment. Vacuum carefully.
• Check motor and wiring: Smell near the blower motor and wiring. If odor is strongest there, have a technician inspect for overheating or loose connections.

Persistent or strong burning smells should always be investigated by a qualified technician.