Which device is specifically used to restrict the passage of flame in ducts and air transfer openings?

The device used to restrict the passage of flame in ducts and air transfer openings is a fire damper. Fire dampers are specifically designed to close automatically when they detect heat, effectively preventing flames from spreading through ductwork or openings between fire-rated barriers. This is crucial in maintaining the integrity of fire-rated walls and ceilings, as it helps control and contain potential fire hazards within a building.

Fire dampers play a key role in fire protection systems by ensuring that, in the event of a fire, flames and smoke do not travel through the ventilation system, which could compromise safety and increase damage. They are often required by building codes and fire safety regulations in various applications, including commercial and residential buildings.

In contrast, a smoke damper is intended to control the movement of smoke rather than flames, serving a different function in fire safety. A combination damper may integrate both smoke and fire damper capabilities, but the primary focus in this question is on restricting flames specifically. A heat exchanger, on the other hand, is used to transfer heat between two fluids and does not serve any role in fire containment. Thus, the unique capability of a fire damper to address flame spread makes it the correct choice.