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Section 917 Post-Fire Smoke Purge Systems

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917.1 Scope and Purpose
The purpose of this section is to establish minimum requirements for the design and installation of post-fire smoke purge systems, which are intended for the timely restoration of operations and overhaul activities once a fire is extinguished. Post-fire smoke purge systems are not intended or designed as life safety systems and are not required to meet the provisions of Section 909. Post-fire smoke purge systems shall be required in:
  1. High-rise buildings subject to Section 403.
  2. Buildings with any story exceeding 50,000 square feet (4645.2 m2) in floor area.
  3. Building with spaces exceeding 100 feet (30 480 mm) from natural ventilation openings. Natural ventilation openings shall consist of operable windows and doors of at least 5 percent of the floor area or roof vents per Section 910.
  4. High-piled stock or rack storage in accordance with the New York City Fire Code.

    Exceptions: A post-fire smoke purge system is not required in Group R-2 occupancies where either of the following conditions exists:
    1. Openable windows. A post-fire smoke purge system is not required where every habitable room located in dwelling units is provided with windows complying with Chapter 12 and all of the following:
      1. Minimum window area. Each required window shall provide at least 12 square feet (1.1 m2) of glazed area. The total area of all such windows shall not be less than 10 percent of the floor area of the room or space served.
      2. Minimum openable area. Each required window shall provide a minimum of 6 square feet (0.56 m2) of openable area. The total area of all such openings shall not be less than 5 percent of the floor area of the room or space served. In addition, each required openable area shall be:
        1. Located wholly at least 30 inches (762 mm) above the finished floor; and
        2. Fully openable to the minimum 6 square feet (0.56 m2), at all times and without limiting stops or devices. Such openings may be achieved through the use of double-hung, sliding, or similar types of windows. However, in the event of the use of casement-, hopper-, pivot-, or awning-type windows, such windows shall satisfy the requirements of this section only when they open to at least 75 degrees (1.22 rad).
      3. Window guards. This exception shall not apply where the type of window guards installed in compliance with Section 27-2043.1 of the Administrative Code and Section 131.15 of the New York City Health Code requires the installation of limiting devices or stops.
    2. Smokeproof enclosures. A post-fire smoke purge system is not required where all exits are constructed as smokeproof enclosures in accordance with Section 1023.11.
917.2 Post-Fire Smoke Purge Systems in Occupancy Groups Other Than R-2
917.2.1 General Design Requirements
Post-fire smoke purge systems are permitted to use dedicated equipment, the normal building HVAC system or other openings and shall have the capability to exhaust smoke from occupied spaces. Smoke removal may be by either mechanical or natural ventilation, but shall be capable of removing cold smoke. Smoke removed from a space must be discharged to a safe location outside the building and shall not be recirculated into the building in accordance with the New York City Mechanical Code.
917.2.2 Exhaust Capability
The system shall have an air supply and smoke exhaust capability that will provide a minimum of 6 air changes per hour or 1 cubic foot per minute per square foot (cfm/ft2) (0.00508 m3/s • m2), whichever is greater. The system need not exhaust from all areas at the same time, but is permitted to be zoned based on the largest fire area served. For the purpose of calculating system size, the height of a compartment shall be considered to run from slab to slab and include the volume above suspended ceilings. Provisions shall be made for sufficient make-up air. The provisions may include operable windows, doors, building leakage, or mechanical systems. In buildings having occupied floors located less than 75 feet (22 860 mm) above the lowest level of Fire Department vehicle access, breakable windows may be utilized.
917.2.3 Operation
The post-fire smoke purge system shall be operated by manual controls that are part of the fire command center, in accordance with Section 911, or fire alarm control unit when a fire command center is not required. Such control center or panel shall display a graphic indicating the portions of the building served by each post-fire smoke purge system. When a system is zoned into areas of operation less than the entire building, each zone shall have an individual control. Fire Department manual controls of post-fire smoke purge systems shall not override the manual or automatic operation of the smoke control system. Such Fire Department manual controls shall override the fire shutdown signal from the fire alarm system.
917.2.4 Interior Exit Stairways or Ramps or Exit Passageways in Occupancies Other Than Group R-2
Interior exit stairways or ramps or exit passageways shall not be used as a portion of the post-fire smoke purge system in occupancies other than Group R-2. Doors in interior exit stairways or ramps or exit passageways shall not be permitted to be used as a portion of the post-fire smoke purge system. Air transfer and duct openings associated with the post-fire smoke purge system shall not be permitted in the interior exit stairway or ramp or exit passageway.
917.3 Post-Fire Smoke Purge Systems in Occupancy Group R-2
Post-fire smoke purge systems in Group R-2 occupancies shall comply with either Section 917.3.1 or 917.3.2. Smoke removed must be discharged to a safe location outside the building and shall not be recirculated into the building in accordance with the New York City Mechanical Code.
917.3.1 Stair Ventilation
The top of all enclosed exit stairs shall be provided with a reversible fan system capable of introducing fresh air or exhausting air at a rate of 6 air changes per hour or 1 cubic foot per minute per square foot (cfm/ft2) (0.00508 m3/s • m2), whichever is greater, based on the area of the largest floor. Such system shall be operated by manual controls that are part of the fire command center, as per Section 911, or fire alarm panel when a fire command center is not required. Such control center or panel shall display a graphic indicating the portions of the building served by each post-fire smoke purge system. The operation of such system shall be controlled by Fire Department personnel by manually opening stair doors at the appropriate story.
917.3.2 Corridor Ventilation
The ducts and fans that provide fresh air supply to the public corridors in accordance with the New York City Mechanical Code shall be provided with reversible fans and duct sizes capable of introducing fresh air to or exhausting air from the corridor at a rate of 6 air changes per hour or 1 cubic foot per minute per square foot (cfm/ft2) (0.00508 m3/s • m2), whichever is greater, based on the area of the largest apartment plus the area of the public corridor. Such system shall be operated by manual controls that are part of the fire command center, as per Section 911 of this code, or fire alarm panel when a fire command center is not required. Each floor to be ventilated shall be by individual controls. Such control center or panel shall display a graphic indicating the portions of the building served by each postfire smoke purge system.
917.4 Maintenance
The building owner shall maintain post-fire smoke exhaust systems in good operational condition. Records of testing shall be maintained on the premises for inspection by the department and Fire Department personnel.

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