I believe you are talking about two different pieces of kit here. The basic one is a 're-breather' when you exhale and inhale out of a bag (as exhaled air still has about 80% oxygen content). Fairly basic, not much training required.
The second one is a mini 'aqua-lung', i.e. bottle of compressed air. Our helicopter pilots were issued them (CHC) and hey-presto, they were taken off them again. I believe it was due to product liability, training, legal stuff.