FSD HVAC Systems & Airflow Control 5 — Questions and Answers
Question 1: Under NFPA 105, smoke dampers in smoke control systems must be inspected and operationally tested at what minimum frequency after the first year of service?
- Every 6 months
- Every year
- Every 2 years
- Every 4 years (Correct answer)
Correct answer: Every 4 years
NFPA 105 requires operational testing of smoke dampers every 4 years (after the initial 1-year test), although authorities having jurisdiction may require more frequent testing.
Question 2: A corridor smoke damper that fails to close during an operational test should be:
- Tagged out of service and the deficiency reported to the building owner for repair (Correct answer)
- Manually held closed with wire until the next scheduled maintenance
- Left in place since corridors are protected by sprinklers
- Bypassed in the fire alarm panel to prevent nuisance alarms
Correct answer: Tagged out of service and the deficiency reported to the building owner for repair
A failed smoke damper must be taken out of service, documented, and reported to the building owner for prompt repair; no workarounds that leave the smoke control system impaired are acceptable.
Question 3: When multiple smoke dampers are connected to a single exhaust fan in a shaft smoke exhaust system, which control arrangement is required?
- All dampers open simultaneously regardless of fire floor
- Only the damper on the fire floor opens; all others remain closed (Correct answer)
- Dampers open sequentially from lowest to highest floor
- All dampers close and the fan exhausts through a dedicated roof bypass
Correct answer: Only the damper on the fire floor opens; all others remain closed
In a shaft exhaust smoke control system, only the damper on the floor of fire origin opens to direct exhaust from that floor; closing all other dampers maximizes smoke extraction at the fire floor.
Question 4: A fire damper installed in a duct that passes through a 2-hour fire-rated floor assembly must be rated to resist fire for at least how long if the duct is used for non-combustible HVAC service?
- 45 minutes
- 1 hour
- 1.5 hours
- 2 hours (Correct answer)
Correct answer: 2 hours
The fire damper must match the fire-resistance rating of the assembly it penetrates; a 2-hour floor assembly requires a damper with a minimum 2-hour fire-resistance rating.
Question 5: Which of the following best describes the role of a 'position indicator' on a smoke damper actuator?
- It measures duct static pressure upstream of the damper
- It provides a local and/or remote signal confirming whether the damper is open or closed (Correct answer)
- It adjusts blade angle to regulate airflow volume
- It initiates damper closure independent of the FACP
Correct answer: It provides a local and/or remote signal confirming whether the damper is open or closed
A position indicator (end switch or feedback signal) confirms the actual blade position to the fire alarm or building automation system, verifying the damper has fully responded to its control command.
Question 6: In a hospital HVAC application, smoke dampers in isolation rooms are required to maintain which airflow relationship to control infection and smoke simultaneously?
- Positive pressure relative to the corridor at all times, including during fire alarm
- Negative pressure relative to adjacent spaces under normal conditions, with smoke control taking precedence during alarm (Correct answer)
- Equal pressure to adjacent spaces to prevent any airflow across the boundary
- Positive pressure during normal operation, switching to 100% exhaust only when a smoke detector activates inside the room
Correct answer: Negative pressure relative to adjacent spaces under normal conditions, with smoke control taking precedence during alarm
Infection-control isolation rooms are maintained at negative pressure under normal conditions, but IBC and NFPA 90A require the smoke control sequence to override HVAC operations during a fire emergency.
Question 7: What is the effect of installing a fire damper in a supply duct without providing adequate clearance for the damper blades to fully open?
- The damper will overheat and fail prematurely
- Restricted blade travel reduces airflow and may prevent full damper closure during a fire (Correct answer)
- The fusible link will activate at a lower temperature due to increased turbulence
- There is no functional impact as long as the damper is listed
Correct answer: Restricted blade travel reduces airflow and may prevent full damper closure during a fire
If blade travel is restricted by insufficient clearance, the damper cannot achieve its rated open position (reducing system airflow) or its rated closed position (compromising fire protection).
FSD HVAC Systems & Airflow Control 5
Under NFPA 105, smoke dampers in smoke control systems must be inspected and operationally tested at what minimum frequency after the first year of service?