Furnace or ductwork makes loud banging or popping noises when starting or stopping

Safety first: Most work is external, but turn off power if removing panels.

• Open registers: Ensure most supply registers are open to reduce static pressure.
• Inspect ductwork: Look for oil-canning (flexing) sheet metal. Reinforce with additional bracing or stiffeners if accessible.
• Filter and coil: Replace dirty filters and have the evaporator coil (if present) cleaned to reduce restriction.
• Adjust blower speed (advanced): A technician can adjust blower speed taps or ECM settings to reduce pressure spikes.

While often not dangerous, severe banging can indicate duct design issues that may require professional correction.