Automatic sprinklers installed in exhaust duct systems shall be hydraulically designed to provide 0.5 gallons per minute (gpm) (1.9 L/min) over an area derived by multiplying the distance between the sprinklers in a horizontal duct by the width of the duct. Minimum discharge shall be 20 gpm (76 L/min) per sprinkler from the five hydraulically most remote sprinklers.
A separate indicating control valve shall be provided for sprinklers installed in exhaust ducts.
Drainage shall be provided to remove sprinkler water discharged in exhaust ducts.
Where corrosive atmospheres exist, exhaust duct sprinklers and pipe fittings shall be manufactured of corrosion-resistant materials or coated with approved materials.
Sprinklers in exhaust ducts shall be accessible for periodic inspection and maintenance.