Abstract: A warning valve arrangement is provided in a breathing apparatus for divers. The breathing apparatus includes a breathing circuit which functions as a closed circuit during a rebreathing phase and a dosing or supply bottle which is alternately connected through a dosing valve to (i) a breathing gas container, from which the dosing bottle is filled, and (ii) the breathing circuit, into which the contents of the dosing bottle are discharged. The breathing circuit comprises a warning valve, which in a closed state at least obstructs inhalation from a breathing bag connected to the breathing circuit. A timing and pressure sensing control device is connected to a supply conduit which interconnects the dosing bottle and the breathing circuit, and, responsive to pressure variations in this supply conduit, causes the warning valve to assume the open state for enabling rebreathing in the breathing circuit.