adjoining areas. The system capacity shall be based on the NFPA 92B and
Uniform Building Code (UBC-1994 edition) Sections 402 and 905 requirements.
system capacity shall be performed by the fire protection engineer.
2.13.2.6.3 The smoke removal system should be activated manually as well as
automatically. In the automatic mode, either a sprinkler flow switch, or a
grid of the beam type of smoke detectors should energize the smoke removal
system. The sprinklers are usually installed at 17 m (55 feet) or below.
2.13.2.6.4 The make-up air system for the smoke removal, if required, will
vary with the layout of the atrium and the surrounding spaces. Normally, upon
activation of the smoke removal system, the dedicated air-handling unit
serving the atrium, for its normal cooling and heating requirements, should
be designed to go to 100 percent outdoor air mode. The additional make-up
air, to comply with the code, should be brought in by a dedicated make-up air
unit. This unit should operate during the smoke removal mode only. Depending
upon the severity of weather, 4 degrees C (40 degrees F) or below, the make-
up air should be heated to 12 degrees C (55 degrees F) temperature. For
milder climate, the make-up air can be admitted to the atrium directly from
outdoor, with or without ductwork, depending upon the physical configuration
of the atrium and the surrounding spaces. The use of the building air from
the other air-handling units serving the occupied spaces shall be avoided to
prevent any possibility of contamination.
2.13.2.6.5 HVAC equipment used in smoke control system shall conform to NFPA
92B, 1995 edition and UBC, 1994 edition requirements.
2.13.2.7 STAIRWELLS: Pressurization of stairwells is not required.
2.13.2.8 ELEVATOR SHAFT VENTING
2.13.2.8.1 Rule 100.4 of ANSI.1, Elevator Safety Code requires venting of all
elevator hoistways. Provide normally closed, two-position motorized dampers
in hoistway vents. See VA Standard Detail 15900-18. Vent dampers shall open
when smoke is detected by the space detector located at the top of each
elevator hoistway.
2.13.2.8.2 There are two automatic methods by which hoistway vent dampers
shall operate. Select one of the methods depending upon the following:
(a) The first method is via a system of smoke detector when sprinklers are
provided at the top of the hoistway.
(b) The second and more common method is via a 120V single station smoke
alarm triggered by the smoke detector that is not connected to the building
fire alarm system. This method shall be applied when sprinklers are not
required at the top of the elevator hoistway (non-combustible shaft
construction and elevator cabs meet flame spread requirements per ASME
A17.1). The VA Fire Protection Design Manual does not require this smoke
alarm. However, VA Elevator Criteria requires this due to its preference.
(c) Regardless of the method selected, the position of the elevator hoistway
vent damper shall be monitored at the ECC.
HVAC DESIGN MANUAL
2-51
HVAC SYSTEMS AND EQUIPMENT
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