Breathable gas supply apparatus

A breathable gas supply apparatus, for connecting with a diving face mask or helmet, the breathable gas supply apparatus being connectable with an inlet and outlet of a rebreather or reclaim unit for a first supply of breathable gas for closed-circuit use, and connectable with a second supply of breathable gas for open-circuit use, wherein, the breathable gas supply apparatus comprises:

• a first valve device for sealing or opening supply from said rebreather or reclaim unit;
• a second valve device for opening or sealing supply from said second supply of breathable gas;
• and
• at least part of a third valve device that is configured to exhaust exhaled gas during open-circuit use and retain exhaled gas during closed-circuit use,
• wherein, the breathable gas supply apparatus is configured such that sealing of the first valve device corresponds to opening of the second valve device enabling switching between the first and second supplies of breathable gas without interruption in supply.