The invention relates to a respirator with a compressed air source (2), with a compressed air source valve (4), a breathing regulator (6), which is connected to the compressed air source valve and which has a pressure reducer and a demand valve, a respirator mask (10), which is connected at a first inlet attachment (11) to the demand valve, a second air source (14), which can either be connected to a second inlet attachment (12) of the respirator mask or is connected to an attachment with direct connection to the demand valve, a switch mechanism (20, 22; 21, 22) with an actuator (20; 21) for switching between compressed-air breathing from the compressed air source via the demand valve or from the second air source, an exhalation valve (30) on the respirator mask, which exhalation valve (30) is adjustable between a first and a second operating state, the internal pressure in the respirator mask being higher in the second operating state than in the first operating state, wherein the actuator (20; 21) of the switch mechanism (20, 22; 21, 22) is provided on the breathing regulator (6), the switch mechanism being designed such that, when switched to compressed-air breathing, it activates the demand valve and sets the exhalation valve (30) to the second operating state and, when switched to breathing via the second air source (14), it deactivates the demand valve and sets the exhalation valve (30) to the first operating state.