Breathing gills are a means for sentient species to breathe (or, more accurately, respire) in atmospheres or substances other than their natural one.
Some species possess the gills naturally, while other gills are genetically engineered. Typically, however, the gills are surgically implanted, usually in the neck for most humanoid species.
- According to G'Kar, they were painful to use, though he never exhibited outward signs of pain. Lyta showed no discomfort either, but it is possible (and highly probable) that the Vorlon models were more efficient.