What kind of apparatus is Bane's mask?

I don't think I really answered the original question.
Regarding real-life variations on Bane's mask, the following snippet can be found on wikipedia:

Other gases or vapors which produce general anesthesia by inhalation include nitrous oxide, cyclopropane and xenon. These are stored in gas cylinders and administered using flow meters, rather than vaporizers

I found a couple of real world images that struck a chord - the first looks like the masks worn in Batman Begins (in shape only, not in function)

and the second image is of a concept mask for firefighters which could be attached to gas cylinders. I have to say though, that no cylinders were apparent on Bane's costume.