A valve controls the discharge of fluid stored under pressure in cylinders (4) and includes a body (2) with a fluid inlet hole (3), a fluid outlet hole (5), and a sealing shaft (6) whose movement, determined by release means (7), opens or closes the fluid passage The release means (7) includes at least one pneumatic actuation hole (11) with non-return valve (12) and a hermetic chamber (10) associated with said sealing shaft (6), a pressure cartridge (8) of compressed gas associated with an electric and manual actuator (9) external to the body (2) and the hermetic chamber (10), which, transmits the motion to a rod (15) linked to said sealing shaft (6). A spring (16) tends to keep the sealing shaft (6) closed, when the pressure is zero or when the cylinder (4) is empty.