Why does my furnace smell burning?

A furnace emitting a burning smell is a relatively common occurrence that usually points to routine seasonal burn-off or an underlying mechanical or electrical issue. The most frequent and harmless cause happens when you turn on your heating system for the very first time in autumn; accumulated dust, pet hair, lint, and debris baked onto the metal heat exchanger burn off rapidly, producing a dusty burning odor that typically dissipates within a few hours. However, if the burning smell is sharp, pungent, and resembles melting plastic or electrical wiring insulation, it indicates a serious hazard such as a failing blower motor overheating, a jammed inducer fan, or a shorted electrical component on the control board. You can verify the source by inspecting the filter and wiring, turning off the system immediately if electrical burning persists.