FSD HVAC Systems & Airflow Control 3

Question 1

A smoke damper installed in a smoke control system must be capable of holding which minimum leakage class per UL 555S?

Accepted Answer

Class III

Answer

UL 555S requires smoke dampers used in smoke control systems to meet at least Class III leakage (less than 4 cfm/ft² at 1" w.g.), though Class I or II provides better performance.

Question 2

When a smoke damper is used in a pressurized stairwell smoke control system, which operational mode is most common?

Accepted Answer

The damper remains closed to maintain positive pressure in the stairwell

Answer

In pressurized stairwell systems, smoke dampers are kept closed on the stairwell side to maintain positive pressure, preventing smoke from entering the egress path.

Question 3

What is the maximum duct velocity at which a fire damper is considered to be operating in a 'static' system for UL 555 listing purposes?

Accepted Answer

There is no velocity limit for static systems

Answer

For static fire damper installations, the fan must shut down before the damper closes; the UL 555 static listing does not specify a maximum duct velocity because closure occurs with no airflow.

Question 4

Which building system typically provides the control signal that causes a smoke damper to close during a fire event?

Accepted Answer

Fire alarm control panel (FACP)

Answer

The fire alarm control panel monitors smoke detectors and, upon detection, sends a control signal to smoke damper actuators to close them as part of the smoke control sequence.

Question 5

Duct smoke detectors used to initiate smoke damper closure must be listed under which standard?

Accepted Answer

UL 268A

Answer

UL 268A, Smoke Detectors for Duct Application, covers detectors designed to sample air within HVAC ducts and trigger smoke damper closure.

(FSD) Fire and Smoke Damper Certification Practice Test

(FSD) Fire and Smoke Damper Certification Practice Test

FSD HVAC Systems & Airflow Control 3