Elevator Smoke Control - Simplex 4100U Application Manual

Designing a Dedicated Smoke Control System,
Elevator Smoke
Control
Most elevators do not have smoke protection, fire protection, or other features necessary for them
to be considered as a means for fire evacuation. Elevator systems not specifically designed and
built for fire evacuation should not be used in fire situations.
The elevator smoke control system is intended to prevent smoke flow to other floors by way of the
elevator shaft. Elevator shafts present a special menace with regards to smoke control. An elevator
shaft makes a perfect chimney to draw smoke into the upper levels of a building. Since elevators
usually have openings on each floor, and the seals on the elevator doors are often poor, the
elevator shaft can become a mechanism to spread smoke throughout a building. Smoke control in
an elevator shaft is an important consideration in the overall smoke control plan.
The problems resulting from smoke migration through elevator shafts are illustrated by the
MGM Grand Hotel fire. Although the fire occurred on the ground floor, the smoke from that fire
migrated through the elevator shafts to the upper floors resulting in a number of fatalities.
An obvious solution to this problem is to pressurize the elevator shafts, as shown in the figure
below. However, pressurizing an elevator shaft presents a number of problems. While the elevator
doors can be fitted with improved seals and rubber sweeps, these systems will not totally eliminate
air leakage. Also, most elevator shafts are not designed to be pressurized. They often have large
openings at the top where the cables feed into the winding room. Shafts are often constructed of
porous material that cannot contain the air pressure. And since most shafts are not designed to be
inspected after the elevators are installed, finding and repairing cracks that would let smoke
infiltrate or pressure escape is difficult.
Smoke
Figure 1-9. Pressurizing an Elevator Shaft to Prevent Smoke Migration
Even if the shaft is pressurized, another primary problem is caused by the transient pressures
produced when an elevator car moves inside the shaft during a smoke emergency. This "piston
effect" can pull smoke into a normally pressurized elevator lobby or elevator shaft. For example,
an elevator car moving down from the top of the shaft may create a small low air pressure zone
near the top of the shaft, which can pull smoke from the fire zone into the shaft.
At the present time, these issues have not been resolved. Pressurizing the elevator shafts so that
the elevators can operate during a smoke emergency is still being studied.
IMPORTANT: In general, elevators should not be used as an escape route during
an evacuation.
Continued
1-18
Special Smoke-Proof
Elevator Doors
Elevator
Low Pressure
Area Created by
Elevator Door