Damper (louvre)

ISO 10628-2 / HVAC practice (ISO 14617-8)

Drawn as

A rectangle across the duct with several parallel slanted blades inside.

Meaning

Duct damper on HVAC, fired-heater stack or fan systems. A fire damper (FD) closes on fire; a gas-tight damper isolates enclosures on gas detection. No dedicated component.

Variants

Single-blade dampers look like a butterfly valve on a duct
Fire dampers may be marked FD or carry a fusible-link note
Motorised dampers carry an M actuator