Dry and Preaction Systems require a dependable source of clean dry air under the proper pressure. The air supply must be adequate to restore normal air pressure within a time specified by the authority having jurisdiction. N.F.P.A. requirements is 30 minutes for dry pipe systems. Proper air regulation should be provided for all dry systems and is extremely important. If pressure is too low, the dry valve may accidentally trip when subjected to surges in water supply pressure. If pressure is too high, the time between the opening of a sprinkler and the flow of the water from the sprinkler may be unacceptably long. Very high pressure also can damage the dry valve. Design air pressure is specified by the dry valve manufacturer. Air supplies may be provided by plant air systems, individual air compressors with or without tanks, and a compressed gas (nitrogen or dry air) in cylinders. (See Technical Datasheet for further details)