Honeywell AUTOMATIC CONTROL, Engineering Manual

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ENGINEERING MANUAL OF AUTOMATIC CONTROL
SMOKE MANAGEMENT FUNDAMENTALS
173
Smoke Management System, Active: A system that uses fans
to produce airflows and pressure differences across
smoke barriers to limit and direct smoke movement.
Smoke Management System, Passive: A system that shuts
down fans and closes dampers to limit the spread of
fire and smoke.
Smoke Control Zone: An indoor space enclosed by smoke
barriers, including the top and bottom, that is part of a
zoned smoke control system (NFPA 92A).
Smoke Damper: A device designed to resist the passage of air
or smoke that meets the requirements of UL 555S,
Standard for Leakage Rated Dampers for Use In
Smoke Control Systems.
Stack Effect: A movement of air or other gas in a vertical
enclosure induced by a difference in density between
the air or other gas in the enclosure and the ambient
atmosphere. The density difference is caused by
temperature-pressure differences between the air
inside a building and the air outside a building. The
air inside the building moves upwards or downwards
depending on whether the air is warmer or cooler,
respectively, than the air outside.
UL: Underwriter’s Laboratories Inc.
UPS: Uninterruptible Power Supply.
OBJECTIVES
Designing a smoke management system requires agreement
on the system objectives. The following is a partial list of
potential system objectives:
— Provide safety for the occupants
— Extend egress time
— Provide safe egress route
— Provide safe zones (tenable environment)
— Assist firefighters
— Limit property damage
— Limit spread of smoke away from fire area
— Clear smoke away for visibility
— Provide elevator usage during fires as an egress route
for the handicapped
DESIGN CONSIDERATIONS
GENERAL
Four points must be stressed in developing a smoke
management system:
1. The smoke management system can be properly designed
only with agreement on the objectives of the system.
2. The smoke management system must be designed as a
complete mechanical control system that is able to
function satisfactorily in the smoke management mode.
The smoke management system should be designed
independently of the HVAC system and then integrated,
where feasible, without sacrificing functionality of the
smoke control system.
3. The smoke management system must be designed to be
reliable, simple, and maintainable.
4. The smoke management system must be designed to
minimize the risks of failure and must be tested
periodically. Sensors providing status of operation and
building automation controls providing system
monitoring and printed records can assist in the testing
process.
Present active smoke control systems use active methods and
follow two basic design approaches to preventing the movement
of smoke from the fire zone:
— Providing static pressure differences across penetrations
in smoke barriers, such as cracks around doors.
— Providing adequate velocity of air through large
openings in smoke barriers, such as doors in an open
position.
Although these two methods are directly related, it is more
practical to use one or the other to design with and measure
the results.
Methods used to activate smoke control systems require
careful consideration. For zoned smoke control, care must be
taken in using smoke detectors to initiate a pressurization
strategy. If a smoke detector that is not in the smoke zone goes
into alarm, the wrong smoke control strategy will be employed.
If a pull station is activated from a nonsmoke zone, the wrong
smoke control strategy could again be employed.