<p>A generally block-shaped valve comprises a gas feed passage (6) possessing an inlet (6a) and an outlet (6b), a branch passage 7 possessing an outlet (7a) branched off and communicating with the gas feed passage (6), a body (1) having a tank or chamber (8) formed in the midst of the branch passage (7), a first valve (2) provided in the body (1) for opening and closing the downstream side of the gas feed passage (6) at the downstream side of the place of connection with the branch passage (7) and a second valve (3) provided in the body (1) for opening and closing the branch passage (7) at the upstream side of the tank/chamber (8). <IMAGE></p>