ETL 1110-3-485
15 Oct 97
4.3.3 The floor area covered by an individual foam-water sprinkler system in helicopter hangar
bays will not exceed 1393 m2 (15,000 ft2).
4.3.4 Sprinkler systems will be hydraulically designed to provide a uniform minimum discharge
density of 6.52 liters/min/m2 (0.16 gpm/ft2) over the hydraulically most demanding 1115 m2
(12,000 ft2) of floor area.
4.3.5 The maximum allowable protection area of coverage for a sprinkler will be 12.1 m2
(130 ft2).
4.3.6 The distance between sprinklers on branch lines will be limited to not more than 3.66 m
(12 ft). The distance between branch lines will be limited to not more than 3.8 m (12.5 ft).
4.3.7 Sprinklers will be quick response upright spray type with a temperature rating of 79 oC
(175 oF).
4.3.8 Where foam-water sprinkler systems are supplied from domestic water systems, backflow
preventers of the reduced pressure type will be provided to prevent foam solution from
contaminating the domestic water system. For most applications, individual backflow preventers
will be installed in the fire protection equipment room of the protected facility. For installations
where a single water storage tank serves both domestic requirements and fire demands through
isolated water distribution systems, backflow preventers may be required in the pump house to
preclude foam contamination of the water storage tank.
4.4 Water-Only Sprinkler Systems.
4.4.1 Water-only sprinkler systems may be used only in buildings where the distance from the
floor to the underside of the roof or ceiling does not exceed 12.2 m (40 ft) and where the roof or
ceiling slope does not exceed 167 millimeters/meter (2 inches per foot).
4.4.2 Water-only sprinkler systems will be wet-pipe.
4.4.3 Water-only sprinkler systems will utilize ESFR sprinklers. No other type sprinkler will be
permitted.
4.4.4 The use of ESFR sprinklers in water-only sprinkler systems will comply with all applicable
provisions of NFPA 13. This includes, but is not limited to, the provision that permits ESFR
sprinklers for use only in buildings with the following types of construction:
B-5
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