The tap intended for controlling the flow of a fluid, for example of a gas, comprises a tap body (34), an inner member (36) for opening and closing the passage of the gases, an outer rotary operating handwheel (42), a connector member (40) connecting the operating handwheel (42) to the closing member (36) and a stop mechanism limiting the movement of the operating handwheel (42) and of the opening and closing member (36) in the opening direction of the tap. In order to avoid the tap becoming jammed in the open position, the stop mechanism that limits the movement of the operating member comprises of an abutment (44) and a counterabutment (46) with frontal contact, which are arranged respectively on a rotary element and on the body (34) of the tap, or vice versa.