What is a barometric damper and what does it do?

• A. A damper that modulates natural draft in the furnace, helping to control furnace pressure and combustion air at startup and during operation.
• B. A valve to regulate steam flow.
• C. A device to measure furnace temperature.
• D. A device that vents steam.

Answer: (A)

A barometric damper is a device placed in the furnace flue that automatically adjusts the amount of air entering the combustion zone by responding to stack pressure. It uses a weighted or calibrated damper blade that moves with changes in draft: if the draft through the flue becomes too strong, the damper closes a bit to throttle back the air; if the draft is weak, it opens to allow more air in. This keeps furnace pressure near the desired level and provides a stable supply of combustion air, which is especially important during startup and as firing rates change. It’s not about regulating steam flow, measuring furnace temperature, or venting steam.