Mechanical ventilation systems for the removal or control of products of combustion shall be provided in every building and shall consist of the following:
(a) Within Building Spaces. Supply and exhaust air from HVAC systems or specially designed smoke control systems shall be used to control the movement of smoke, fire gases and heat within buildings. Such systems shall:
(1) Be designed to exhaust the fire zone and create a positive air pressure zone around the fire zone. Such systems shall be activated automatically by the smoke/fire alarm system or water flow.
(2) Automatically go to 100° outside air on activation (no recirculation). Exhaust air shall be directed outside in a manner to prevent it from contaminating the supply air.
(3) Have controls at the central control center and fire command center for override if necessary.
(4) Corridors and elevator lobbies in non-centrally air conditioned apartments, condominiums and non-transient dwellings more than two stories in height shall be pressurized continuously according to NFPA Standard 101-1976 section 11.
(5) Have non-combustible ductwork and shafts through which air will be supplied or exhausted, as required by NFPA 90A Standard 90A-1979 and building code applicable. The size of any air conditioning duct or shaft for exhaust air shall be of such dimension as to provide a minimum of one air change every ten minutes in the largest zone served by that shaft or duct.
(6) Other approved design which will produce equivalent results may be used.
(NOTE: For operating practice and engineering design refer to ASHRAE SYSTEMS MANUAL, chapter 41, 1977 and Measures for Fire Safety in High Buildings 1977, NRCC No. 15764 Supplement to Subsection 3.2.6 of the National Building Code of Canada, 1977.)
(b) Stairways. Unless opening onto an exterior open stairtower, each exit stairway shall be mechanically pressurized with outside air during a fire situation to a minimum of 0.1 inch w.c. across any closed stairway door in a manner approved by the building official and HVAC engineer. In stairways more than eight stories in height air shall be injected at intervals not to exceed eight stories. The maximum degree of pressurization shall be such that the opening of stairway doors can be accomplished with a force not to exceed 24 (twenty-five) pounds applied at the door knob. The pressurization system shall be designed with the assumption that during a fire situation the following doors are intermittently open: the fire floor door, the floor above and the door of exit discharge to ground level from the stairway. The minimum air velocity measured through the three doors when open shall be no less than 150 feet per minute. Pressurized stairwells shall have an operable relief damper.
(c) Elevator Shafts. Elevator shafts shall be protected in a manner approved by the building official to prevent the entry of smoke or other products of combustion, or shall be pressurized to 0.05 minimum to 0.15 maximum inches of water column differential pressure across any elevator door in a manner approved by the building official and HVAC engineer so as not to interfere with elevator door operation.
(NOTE: This is not in conformance with the National Elevator Code.
(d) Systems shall be designed to prevent coil freeze-up in cold climates.
(e) It shall be the responsibility of the designer, or his delegated agent to submit a comprehensive written description of all systems that are installed as a result of this subsection. Copies of this report shall be submitted to the City Fire Department and the City Building Department along with plans for approval.
(Ord. 78-81. Passed 5-8-81.)