A duct or air conditioning (AC) damper is a device used to control the flow of air in an HVAC (heating, ventilation, and air conditioning) system. It is usually located in the ductwork of the system and is operated manually or automatically. The damper is used to regulate the amount of air that is allowed to flow through the ducts. It can be used to regulate the temperature of the air, the amount of air that is circulated, and the amount of air that is allowed to escape from the system. By controlling the flow of air, the AC damper can help maintain a comfortable temperature in the home or office. Additionally, it can help reduce energy costs by preventing the system from running too much or too little. The AC damper is an important part of any HVAC system and should be regularly checked and maintained to ensure that it is functioning properly.