A breathing bag (1) for a closed-circuit respirator (100) has a bag component (2), which encloses an inner volume (3). The bag component (2) can reversibly assume at least one unfolded state (4) and a folded-in state (5). The bag component (2) encloses a larger inner volume (3) in the unfolded state (4) than in the folded-in state (5). Moreover, a closed-circuit respirator (100) is provided, having at least one counter-lung, a filter device, an oxygen source as well as a housing. The counter-lung, the filter device and the oxygen source are arranged in the housing.
