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502.9.4 Explosives.
Squirrel cage blowers shall not be used for exhausting hazardous fumes, vapors or gases in operating buildings and rooms for the manufacture, assembly or testing of explosives. Only nonferrous fan blades shall be used for fans located within the ductwork and through which hazardous materials are exhausted. Motors shall be located outside the duct.
502.9.5 Flammable and combustible liquids.
Exhaust ventilation systems shall be provided as required by Sections 502.9.5.1 through 502.9.5.5 for the storage, use, dispensing, mixing and handling of flammable and combustible liquids. Unless otherwise specified, this section shall apply to any quantity of flammable and combustible liquids.
Exception: This section shall not apply to flammable and combustible liquids that are exempt from the New York City Fire Code.
502.9.5.1 Vaults.
Vaults that contain tanks of Class I liquids shall be provided with continuous ventilation at a rate of not less than 1 cfm/ft
2
of floor area (0.00508 m
3
/(s • m
2
)), but not less than 150 cfm (4 m
3
/min). Failure of the exhaust airflow shall automatically shut down the dispensing system. The exhaust system shall be designed to provide air movement across all parts of the vault floor. Supply and exhaust ducts shall extend to a point not greater than 12 inches (304.8 mm) and not less than 3 inches (76.2 mm) above the floor. The exhaust system shall be installed in accordance with the provisions of NFPA 91. Means shall be provided to automatically detect any flammable vapors and to automatically shut down the dispensing system upon detection of such flammable vapors in the exhaust duct at a concentration of 25 percent of the LFL.
502.9.5.2 Storage rooms and warehouses.
Liquid storage rooms and liquid storage warehouses for quantities of liquids exceeding those specified in the New York City Fire Code shall be ventilated in accordance with Section 502.8.1.
502.9.5.3 Cleaning machines.
Areas containing machines used for parts cleaning in accordance with the New York City Fire Code shall be adequately ventilated to prevent accumulation of vapors.
502.9.5.4 Use, dispensing and mixing.
Continuous mechanical ventilation shall be provided for the use, dispensing and mixing of flammable and combustible liquids in open or closed systems in amounts exceeding the maximum allowable quantity per control area and for bulk transfer and process transfer operations. The ventilation rate shall be not less than 1 cfm/ft
2
(0.00508 m
3
/(s • m
2
)) of floor area over the design area. Provisions shall be made for the introduction of makeup air in a manner that will include all floor areas or pits where vapors can collect. Local or spot ventilation shall be provided where needed to prevent the accumulation of hazardous vapors.
502.9.5.5 Bulk plants or terminals.
Ventilation shall be provided for portions of properties where flammable and combustible liquids are received by tank vessels, pipelines, tank cars or tank vehicles and which are stored or blended in bulk for the purpose of distributing such liquids by tank vessels, pipelines, tank cars, tank vehicles or containers as required by Sections 502.9.5.5.1 through 502.9.5.5.3.
502.9.5.5.1 General.
Ventilation shall be provided for rooms, buildings and enclosures in which Class I liquids are pumped, used or transferred. Design of ventilation systems shall consider the relatively high specific gravity of the vapors. Where natural ventilation is used, adequate openings in outside walls at floor level, unobstructed except by louvers or coarse screens, shall be provided. Where natural ventilation is inadequate, mechanical ventilation shall be provided. The natural ventilation design shall be approved for each specific application by the commissioner prior to installation and/or use.
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