Exhaust Ducts Containing Corrosive Vapors

Sprinklers installed in duct systems shall be located at 12-foot intervals, and at changes in direction. The sprinklers shall be hydraulically designed to provide 0.5 GPM over an area derived by multiplying the distance between the sprinklers in a horizontal duct by the width of the duct. A separate indicating control valve shall be provided for sprinklers installed in ductwork. Drainage shall be provided to remove all sprinkler water discharged in ductwork. The sprinklers shall be accessible for periodic inspection and maintenance. (UMC 609.7, NFPA 318 2-1.2.6.1, NFPA 318 2-1.2.6.2, and NFPA 318 2-1.2.6.5). 

All gas cabinets located within the H-6 fab areas must contain sprinklers. In H-2 or H-7 storage rooms, only cabinets containing pyrophoric materials must be sprinklered (see exception to UFC 5105.2). Sprinklering of all cabinets, regardless of the gas which a cabinet will store at the outset of design is recommended. 

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