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flow upward to a relief damper at the top of the shaft.
Dampers are typically of the barometric type in order to
effectively maintain a higher static pressure in the
elevator shaft.
Atrium smoke control systems
Atrium smoke control, another dedicated smoke control
type, focuses upon exhausting smoke products at a rate
which will maintain tenability and help preserve visibility
at lower levels of the atrium. Atrium smoke control
systems are governed by NFPA 92B, Guide for Smoke
Management in Malls, Atria, and Large Areas.
Smoke removal fans at the ceiling must typically provide
the greater of six air changes per hour or 40,000 cfm
(18,800 L/s). Very large atriums must have a ceiling
exhaust system capable of at least four changes per
hour.
Supply air openings for diluting and exhausting smoke
are located on the lowest or next to lowest level and are
sized the design air flow requirements. Larger atriums
may also have fans for supplying makeup air. Openings
for supply air may consist of louvers, dampers, rolling
doors, and pedestrian doors as specified by the smoke
control system designer. Operation of supply air doors or
dampers from the FSCS is required.
Detection of a fire in an atrium is via smoke detectors
mounted on the ceiling, and under floor projections in the
atrium. Beam type detectors are often specified for
larger or taller spaces.
The atrium smoke control system fans and dampers are
normally off or closed. Sequencing of supply openings
with fan startup is part of the VM-1 SCS. Static pressure
control may be, but typically is not, a part of system
operation.
For each of the dedicated system types the final goal is
to create a pressure differential of 0.15 in. to 0.45 in. of
water (37.4 Pa to 112.05 Pa) across a door opening or
on either side of a barrier.
For dedicated systems, the building smoke control
system designer will establish the size of fans, dampers,
and vents. The sequencing of fan operation and damper
controls will also be defined for the VM-1 SCS
designer/installer.
VM-1 Smoke Management Application Guide
Chapter 2: Smoke control system hardware
Nondedicated
Nondedicated mechanical system components are
commonly a part of the building HVAC system. HVAC
systems are used for smoke control to create differential
pressures between the smoke zone and adjacent zones
or areas.
Differential pressurization is typically achieved by
providing adjacent zones with full supply air (100 percent
from the outside) without any return or exhaust in the
adjacent zone. The smoke zone air supply is stopped
and full exhaust of the zone to the outside is
implemented to relieve fire generated pressures or
create a negative pressure in the smoke zone.
Nondedicated smoke control systems include single
zone HVAC systems with direct outside air and direct
exhaust air, single zone systems with common outside
air and common exhaust air, central HVAC systems,
dual duct HVAC systems, multi-zone HVAC systems,
and variable air volume systems. Key FSCS settings
criteria for each of these system types and smoke
control operating positions for devices follow.
Single zone HVAC systems with direct outside air
and direct exhaust air
Single zone HVAC systems most often serve one floor
or a portion of a floor in a multistory building and are
readily adaptable to smoke control use.
Several zones will be used to limit smoke spread by
creating differential pressures around a fire.
See Table 3 on page 34 for control settings.
Single zone systems with common outside air and
common exhaust air
Single zone systems with common outside and exhaust
air receive their outside air from a common outside air
system and are found in multiple floor buildings. HVAC
controls are provided within individually zoned systems.
Single zone HVAC systems can be effectively used to
provide smoke control when smoke dampers are located
at barriers to limit smoke spread.
See Table 4 on page 34 for control settings.
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