F80 Smoke Control and HVAC Systems — Questions and Answers
Question 1: During a high-rise fire, what is the primary purpose of stairwell pressurization?
- To supply fresh air to firefighters climbing the stairs
- To prevent smoke from infiltrating evacuation stairwells (Correct answer)
- To increase the speed of occupant evacuation
- To cool the stairwell temperature during a fire event
Correct answer: To prevent smoke from infiltrating evacuation stairwells
Stairwell pressurization creates a positive air pressure differential that prevents smoke from migrating into the stairwell, keeping evacuation routes tenable for building occupants and firefighters.
Question 2: When a fire is confirmed in a high-rise building, what is the correct action regarding the HVAC system serving the fire floor?
- Increase airflow to dilute smoke concentration on the fire floor
- Leave the HVAC running to maintain occupant comfort on other floors
- Shut down HVAC serving the fire floor to prevent smoke spread through ductwork (Correct answer)
- Switch all units to recirculation mode to filter the air
Correct answer: Shut down HVAC serving the fire floor to prevent smoke spread through ductwork
HVAC systems can rapidly distribute smoke throughout a building via ductwork. Shutting down HVAC on the fire floor — and often the floors immediately above and below — is standard procedure to contain smoke spread.
Question 3: A smoke damper's primary function in a fire is to:
- Direct exhaust smoke toward the roof vents
- Close automatically to prevent smoke migration through duct openings in fire barriers (Correct answer)
- Increase negative pressure in smoke-filled corridors
- Filter particulates before recirculating air to occupied floors
Correct answer: Close automatically to prevent smoke migration through duct openings in fire barriers
Smoke dampers are installed in HVAC ducts where they penetrate smoke barriers. On activation (typically via smoke detector or fire alarm), they close to maintain the integrity of smoke compartments.
Question 4: In a high-rise building, which area is typically maintained at the HIGHEST air pressure during a smoke control event?
- The fire floor corridor
- The elevator lobby on the fire floor
- The protected stairwell enclosure (Correct answer)
- The mechanical equipment room
Correct answer: The protected stairwell enclosure
Protected stairwells are pressurized to the highest level so that when doors are opened, air flows outward into corridors rather than allowing smoke to enter. This maintains tenable conditions in the primary evacuation route.
Question 5: The Fire Safety Director receives an alarm indicating smoke detector activation in the return air plenum. What is the MOST likely concern?
- A false alarm caused by dust accumulation in the sensor
- Smoke is being drawn from a fire location and distributed through the HVAC return system (Correct answer)
- The plenum temperature exceeds the HVAC design rating
- A sprinkler head has discharged water near the duct intake
Correct answer: Smoke is being drawn from a fire location and distributed through the HVAC return system
Return air plenums collect air from occupied spaces before recirculating it. A smoke alarm in the return plenum is a strong indicator that smoke from a fire is entering the HVAC system and risks being distributed building-wide.
Question 6: Under NYC regulations, after the HVAC system is shut down during a fire alarm, who has authority to restart it?
- The building engineer on duty, once the alarm is silenced
- The Fire Safety Director, if no smoke is visible on any floor
- The FDNY incident commander on scene (Correct answer)
- Any trained building staff member after a 10-minute delay
Correct answer: The FDNY incident commander on scene
Once the FDNY is on scene and assumes command, authority over building systems — including HVAC restart — transfers to the FDNY incident commander. The Fire Safety Director must coordinate with and defer to FDNY command.
F80 Smoke Control and HVAC Systems
During a high-rise fire, what is the primary purpose of stairwell pressurization?