Smoke Control and HVAC Systems Flashcards

What normally causes a standard fire damper to close?

Answer: Melting of a fusible link from heat

Fire dampers close when a heat-responsive fusible link, commonly rated about 165°F, melts.

How does a smoke damper differ from a fire damper?

Answer: A smoke damper is controlled by a smoke detector or fire alarm signal to limit smoke movement

Smoke dampers are actuated by detection or control signals to resist the passage of smoke.

A combination fire/smoke damper is designed to:

Answer: Meet both fire damper and smoke damper requirements in one assembly

Combination dampers close on heat and on smoke detection signals, serving both functions.

After a duct detector shuts down an air handler, how should the fan be restored?

Answer: Only after the detector and fire alarm system are reset by authorized personnel

HVAC shutdown remains in effect until the initiating device and the system are properly reset.

Spot-type smoke detectors should not be installed within how many inches of an HVAC supply diffuser?

Answer: 36 inches

NFPA 72 keeps detectors at least 36 inches from supply diffusers so moving air does not dilute smoke.

What problem can strong supply airflow cause for nearby ceiling smoke detectors?

Answer: Smoke being diluted or blown away, delaying detection

High air movement can keep smoke from reaching the detector chamber in time.

A duct detector in a dusty mechanical room keeps reporting a dirty/trouble condition. What is the most likely cause?

Answer: Contaminated sensing chamber

Dust buildup in the detector chamber commonly causes trouble or false alarm conditions and requires cleaning.