WM Keck Science
The design of a lightweight oxygen rebreather set suitable for short duration explorations in foul-air caves is described, together with a discussion of its performance, limitations, and possible improvement.
McFarlane D.A. (1981). "The Design of Oxygen Rebreather Equipment for Use in Foul-Air Speleology." Transactions of the British cave Research Association 8(3): 130-134.