A mask 10 for breathing apparatus incorporates an oronasal mask 40, that is at least partially translucent and is preferably transparent, and a light source to illuminate it. The light source may be one or more LEDs which may be carried on a plug that is removably connectable to a port formed in the mask. Also disclosed is a mask in which the exhalation valve (23, figure 2; 22, figure 3a) operates at a higher pressure when a pressurised air supply is attached to the mask. A spring 27 is normally prevented from opposing operation of the exhalation valve by the tip 31 of lever arm 30. However, connecting a pressurised air supply brings an adaptor to bear on a cam surface 30a of the lever arm and releases the biasing spring to bear on the exhalation valve.