Furnace produces unusual odors when running, such as burning dust or metallic smell.

Safety first: If you smell strong burning plastic, electrical, or smoke, shut off the furnace and investigate immediately.

• Initial season burn-off: A mild burning-dust smell at first startup of the season is common and should dissipate after 30–60 minutes of operation.
• Inspect registers: Check supply registers for toys, plastic, or debris that could be heated.
• Filter and cleaning: Replace the filter and consider having ducts professionally cleaned if dust odors persist.

Persistent metallic, chemical, or electrical odors require professional inspection of wiring, blower motor, and heat exchanger.