A compressed air respirator with prolonged operating time due to rebreathing. The compressed air reservoir includes a compressed air reserve with a connected demand air supply valve, a reversible breathing gas reservoir (4) with a registering device (5) detecting the filling level of the breathing gas reservoir (4), and with an inspiration and expiration line (7, 8) for the user of the apparatus. A valve (6) is connected with the inspiration and expiration line (7, 8) and, on the inlet side, with the compressed air reserve (1) with a demand air supply valve (2) and with the breathing gas reservoir (4) and, on the outlet side, with the ambient air (11) and with the breathing gas reservoir (4). The valve means (6) is cyclically reversed by the registering device (5) in two phases such that depending on the filling level of the breathing gas reservoir (4), the inspiration line (7) is first connected with the compressed air reserve (1) and the expiration line (8) with the breathing gas reservoir (4) during a first phase until the filling level of the breathing gas reservoir (4) reaches an upper reversing point for the valve means (6), so that the inspiration line (7) is connected with the breathing gas reservoir (4) and the expiration line (78) with the ambient air (11) during a second phase until the filling level of the breathing gas reservoir (4) reaches a lower reversing point for the valve means (6) and the latter is again reversed as in the first phase.