High-Rise Building Construction and Compartmentalization Flashcards

What is 'stack effect' in a high-rise building?

Answer: Natural vertical air movement through shafts caused by indoor-outdoor temperature differences

Stack effect drives air and smoke up or down vertical shafts based on temperature differences between inside and outside.

During winter, stack effect in a heated high-rise generally causes smoke in shafts to move:

Answer: Upward

Warm indoor air is lighter than cold outside air, so it rises through stairs, elevator hoistways, and other shafts.

Why can a return-air plenum above a suspended ceiling be a fire hazard?

Answer: It can carry smoke and fire to other parts of the floor without being seen

Ceiling plenums are hidden open spaces that can let smoke and fire spread above the ceiling across compartments.

A fire door in a stair enclosure must be kept:

Answer: Self-closing and latching

Stair doors must close and latch on their own to keep fire and smoke out of the stair enclosure.

A 'fire tower' in older NYC high-rises is best described as:

Answer: An enclosed stairway entered through an open-air balcony or vented vestibule

A fire tower is a smokeproof stair enclosure reached through an outside balcony or vestibule so smoke cannot get into the stair.

Sprayed-on fireproofing applied to structural steel in a high-rise is mainly meant to:

Answer: Delay the steel from losing strength in a fire

Fireproofing insulates steel so it heats more slowly and keeps its load-carrying strength longer during a fire.

Why must vertical shafts such as elevator hoistways and utility chases be enclosed in fire-rated construction?

Answer: To prevent fire and smoke from spreading floor to floor through the shaft

Rated shaft enclosures stop shafts from acting as chimneys for vertical fire and smoke spread.