FLSD High-Rise Fire Behavior and Smoke Control

Question 1

The 'stack effect' in a high-rise building refers to:

Accepted Answer

The natural upward movement of warm air and smoke through vertical shafts caused by temperature and pressure differences

Answer

Stack effect is the movement of air (and smoke) upward through vertical shafts (elevator shafts, stairwells, utility chases) driven by the temperature difference between building interior and exterior. In winter, strong upward stack effect can rapidly carry smoke from lower floors to upper floors.

Question 2

During a high-rise fire, an HVAC system that is NOT placed in smoke control mode can:

Accepted Answer

Distribute smoke from the fire floor to other floors through the ductwork

Answer

Standard HVAC systems recirculate and distribute air across multiple floors. Without being placed in smoke control mode (which typically seals dampers and shifts to exhaust), the system can draw smoke from the fire floor into return ducts and redistribute it to unaffected floors throughout the building.

Question 3

In a high-rise building fire, why is it generally unsafe to evacuate ALL occupants to the street level simultaneously?

Accepted Answer

Stairwells can become dangerously congested, slowing firefighter access and creating panic-related injuries

Answer

High-rise fire strategy typically involves selective (phased) evacuation — the fire floor, the floor above, and often the floor below — rather than total building evacuation. Simultaneously evacuating a 40-story building creates dangerous stairwell congestion, impedes firefighter ascent, and can cause injuries.

Question 4

Smoke entering a pressurized stairwell from the fire floor is MOST likely caused by:

Accepted Answer

A stairwell door being held open, reducing pressure differential and allowing smoke infiltration

Answer

Pressurized stairwells maintain positive air pressure to prevent smoke entry — but only when doors are closed. A propped-open or wedged stairwell door destroys the pressure differential, allowing smoke to enter freely. FLSDs must enforce door discipline during evacuations.

Question 5

The 'defend in place' strategy for occupants in fire-resistive high-rise buildings is MOST appropriate when:

Accepted Answer

Occupants are on floors remote from the fire and evacuation would increase their exposure to smoke in stairwells

Answer

In fire-resistive high-rise construction, the building's compartmentalization often makes it safer for occupants on remote floors to stay in place rather than enter potentially smoke-contaminated stairwells. FDNY directs when and where to evacuate; occupants should not self-initiate descent unless instructed.

FLSD - Fire Life Safety Director Practice Test

FLSD - Fire Life Safety Director Practice Test

FLSD High-Rise Fire Behavior and Smoke Control