SCS Series Manual —
P/N 15712:L 7/18/16
17
General System Components
Concepts of Smoke Control
2.3.2 Purging
Although Pressurization and Airflow have been discussed as the two methods for controlling smoke, it will not always be possible to main-
tain airflows sufficient to prevent smoke from moving through open doors into a protected area. Ideally, doorways will be open for only short
periods of time during evacuation. Smoke that has entered a protected space can be purged or diluted by supplying outside air to the space.
Purging is employed through the use of an exhaust inlet, usually located near the ceiling, and a supply outlet, usually located near the floor.
The supply and exhaust points must be placed far enough apart to prevent the supply air from blowing directly into the exhaust. If the supply
and exhaust points are placed too close, the purging operation will not function properly.
While the process of purging is not an acceptable method of smoke control on its own, it can be used as a supplement to airflow or pressur-
ization.
2.3.3 Door-Opening Forces
A door-opening force is defined as the force required to open a door. During smoke control operation, this force can increase considerably,
especially if pressure differences are being used across partitions. The door-opening force during a fire condition can be described as the sum
of the forces needed to overcome the pressure difference across the door and to overcome the door closer. This factor must be taken into con-
sideration for a smoke control system because unreasonably high door-opening forces can hinder or prevent people from reaching their
escape routes.
2.4 General System Components
In general, all smoke control systems are made up of the following:
•
HVAC equipment (fans, dampers, ductwork, etc.)
•
Control Equipment (fire alarm control panel, fire fighter's smoke control station, HVAC controls)
•
Initiating Devices (smoke detectors, manual pull stations, etc.)
A typical layout is shown in Figure 2.6.
Figure 2.5 Airflow
Control Equipment
Fans
Dampers
Smoke
Detectors
Pull
Stations
Door
Closers
Figure 2.6 Smoke Control System General Components