Strong burning dust smell when the furnace first starts for the season.

Safety: A mild burning dust smell is common at first startup. If you smell burning plastic, electrical, or see smoke, shut off power immediately.

Steps:

• Run furnace: Allow the furnace to run for 15–30 minutes with a few windows slightly open to clear the odor.
• Replace filter: Install a clean filter to capture loosened dust.
• Inspect for unusual signs: If the smell is strong, acrid, or accompanied by smoke, turn off power and inspect for melted wiring or debris on the heat exchanger.

When to call a technician: If the smell persists beyond a few cycles or seems electrical or chemical, have a professional inspect the furnace.