Kidde VM-1 Manual page 25

Smoke control system activation and
deactivation
Smoke control system activation is the initiation of the
operational mode of a smoke control system.
Deactivation is the cessation of the operational mode of
the smoke control system and return of HVAC control to
the building environmental control center. Smoke control
systems usually are activated automatically but can be
manually initiated under conditions deemed appropriate
as a part of the smoke control system design. Under all
operating conditions, the smoke control system must be
capable of manual override.
Loss of building power should be evaluated to determine
if the smoke control system design would function as
intended. The evaluation must consider the position
(open or shut) of smoke dampers upon loss of power
and when the fan systems the dampers served are
shutdown.
Automatic activation or deactivation of a smoke control
system includes all initiating circuit action that results in
the operation of one or more smoke control zones
without manual intervention. Automatic activation will
usually come from smoke detectors and waterflow
switches.
Smoke control system activation should begin
immediately upon receipt of an activation command.
Sequencing of smoke control components (fans,
dampers, ducts, and louvers) is necessary to prevent
physical damage to the equipment. Over-pressurization
of a duct due to early or improper damper operation
could result in damage to the duct and an inability to
effectively control smoke in a zone.
NFPA 92A, Recommended Practice for Smoke control
Systems, establishes the maximum response time for
individual components to reach a fully operational mode.
Fans must reach the specified flow rate within
60 seconds and confirm the state has been reached at
the smoke control panel and the FSCS. Completion of
smoke damper travel to either the fully open or the fully
closed state must be accomplished within 75 seconds of
signal initiation.
Note:
Local codes, like UBC, may specify other times.
Check all applicable codes and use the time limit
required.
VM-1 Smoke Management Application Guide
Chapter 1: Fire geometry and smoke movement in buildings
Initiating circuits
Smoke control system initiating circuits may contain the
same alarm initiating devices found in a standard
VM-1 fire alarm system and initiating device circuit (IDC).
Alarm signal initiating devices used for smoke control
may also serve a dual-purpose, initiating alarm
notification or control functions required under NFPA 72.
A smoke control system initiating device, when
activated, initiates predetermined system sequences.
Detection
Smoke control system initiation using smoke detectors is
most common. Since the goal of smoke control systems
is most often to maintain tenability in a zone or space,
heat or flame-type detection is not considered
responsive enough for use in a smoke control system.
Heat detectors in maintenance or similar rooms
incidental to the area protected or locations where
smoke detectors cannot be effectively installed may be
connected to the smoke control system.
Detection using either photoelectric or ionization spot
type smoke detectors should be based upon the space
protected. Smoke development and travel are influenced
by ceiling configuration and height, burning
characteristics of materials, fuel arrangement, room
geometry, and HVAC systems installed.
Some large volume spaces, such as atriums, have been
reported to experience temperatures of up to 200°F
(93.3°C) because of solar loads. Detectors in these
areas need to be capable of operating in this day-to-day
environment. Installation sheets for detectors contain
operating temperature ranges for detectors. Signature
Series smoke detectors should be installed in
accordance with the requirements contained in the
Signature Series Intelligent Smoke and Heat Detectors
Applications Bulletin (270145).
Concerns over smoke stratification and detector access
in large or high ceiling areas, such as atriums, is
increasingly leading designers to specify projected
beam-type smoke detectors. Projected beam detectors
work on the principle of light obscuration. A beam of
infrared light is transmitted across the protected area
and is monitored by a receiver. Smoke particles entering
the beam path can either absorb or scatter the beam of
light, causing a reduction in light received. When the
reduction in light received reaches a threshold, an alarm
signal is generated.
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