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 possessed breathing gills naturally, while others were genetically engineered to have them. Breathing gills could be surgically implanted, usually in the neck for 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.