A pre-action sprinkler system consists of a sprinkler system and an electrical detection system with water held back by the pre-action valve and pressurized air in the sprinkler pipework. In the event of the operation of the electrical detection system the pre-action valve operates and allows water into the sprinkler pipework.
BS 7273-3:2000 gives recommendations for the design, installation, operation and servicing of electrical equipment used for the actuation of pre-action sprinkler systems.