Supply air plenums that discharge air from the face rather than from the bottom or into the exhaust hood and that are isolated from the exhaust hood by the continuously welded shell extending to the lower outermost perimeter of the entire hood assembly shall not require a ______.

• A. Water-Spray System
• B. Return Damper
• C. Smoke Detector
• D. Fire-Actuated Damper

Answer: (D)

When a supply air plenum is designed to discharge at the face and is separated from the exhaust hood by a continuous welded shell that extends to the hood’s outer perimeter, there is a solid physical barrier between the hood and the plenum. That barrier stops flame, heat, and smoke from moving from the hood into the supply plenum, so there’s no duct path that an automatic fire-actuated damper would need to isolate during a fire. Because of this separation, the fire-actuated damper is not required in this configuration.

Water-spray systems or smoke detection may still be used where required by other parts of the code or system design, and return dampers serve different purposes, but they don’t negate the fundamental reason this specific damper is not needed.