A post valve yoke (35, 150) is operative to engage with a tank or cylinder (154) for placing the tank in fluid communication with a high pressure source of gas. The yoke includes a yoke body (148). The upper ends of the yoke body include a bore (160). A plunger (158) is operative to slide through the bore. The yoke body includes an opening (146) that is operative to receive a post valve (152) of the tank. The yoke is operative to urge the post valve with the plunger into sealed engagement with a passageway (144) in the lower end (174) of each yoke responsive to the movement of a lever arm (156) in pivoting connection with the plunger. A trigger lock (176) is operative to lock the lever arm in an engaged position to prevent the yoke from accidently disengaging with the post valve.