Abstract: A closing device with a valve having a high speed reaction. A dome shaped valve is forced open by applying pressure to a piston which is attached to the dome. The opening pressure is provided by an electromagnetic jack and is transmitted through a lock which has a releasing threshhold. The displacement of the piston biases a return spring into a compressed state. Force applied to the lock by a solenoid counteracts the force of the return spring so as to keep the lock locked and thus keep the dome open. When enough force is applied to the dome so as to overcome the threshhold of the lock, or if the lock is intentionally released, the piston is freed and the return spring quickly forces the dome to a closed position.