A respirator for a compressed air breathing apparatus including a lung machine controlled by a control membrane and an expiratory valve with an air outlet. The air outlet of the expiratory valve and the control membrane of the lung machine are covered by a common lid spaced from the expiratory valve and control membrane, with there being at least one air discharge opening on the lid that forms a purging space around the control membrane through which air from the air outlet passes so as to move against the control membrane and to the at least one discharge opening.