MIL-HDBK-1003/3
dampers. Avoid using balancing dampers for industrial
ventilation (IV) systems. Design IV ductwork so that the system
will function properly without balancing dampers. Do not use
balancing dampers when designing a VAV system. A VAV system with
ductwork designed using the static regain method and properly
sized VAV terminal units is inherently self-balancing. Refer to
Appendix C for additional information.
6.1.3.8
Fire Dampers and Smoke Dampers
a) Fire Dampers. The term "fire damper" usually means
a curtain type damper which is released by a fusible link and
closes by gravity or a mechanical spring. Fire dampers are
mounted in walls of fire rated construction to ensure integrity
of the space. Fire dampers should be installed where the passage
of flame through a fire rated assembly is prohibited. Refer to
par. 4.1.3 for duct pressure classification requirements.
b) Combination Fire and Smoke Dampers. The term
"combination fire and smoke damper" usually means a fire damper
which is automatically controlled by an external source (such as
a fire alarm control panel or energy management system) to stop
passage of both fire and smoke. Combination fire and smoke
dampers should be installed where passage of fire or smoke is
prohibited. Activation of combination fire and smoke dampers can
be by several methods including pneumatic damper operators,
electric damper operators, and electro-thermal links.
Electro-thermal links include explosive squibs which are not
restorable and McCabe type links which are restorable.
Pneumatically operated dampers are the preferred method of damper
activation, and should be configured in the fail-safe mode such
that loss of pneumatic pressure will result in dampers closure.
In electronic data processing rooms, combination fire
and smoke dampers should be installed in walls with a fire
resistance rating of 1 hour or greater. In other type spaces,
either fire dampers or combination fire and smoke dampers should
be installed in walls with a fire resistance rating of 2 hours or
greater. Where a smoke damper is required to stop passage of
smoke through a barrier (e.g., hospitals), the installation of a
combination fire and smoke damper is required.
c) Mounting Details. Fire dampers and combination
fire and smoke dampers must remain in the wall during a fire.
Though ductwork may collapse, the damper should remain in the
fire rated assembly, therefore, indicate on drawings the details
for attaching dampers to the wall. Use UL listed firestopping
materials between the damper collar and the wall, floor, or
ceiling assembly where penetrated.
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