I was looking over SR2's Bodyguard archetype and got to the Air Filtration System. I wondered how it worked according to the game mechanics. Buried in the gear description (maybe not really buried, but I never noticed it before), it says the toxin or rated gas makes a test vs (Rating)TN, and results in reduced Power/Force. Then says it protects from smoke and most gases. The 'hidden' part follows: "A specialized form, the artificial gill, allows the user to filter oxygen from water."

Under the Gear Cost listings, there is no gill form listed. Does this mean all "Filtration System - Air" have the gill feature? Or it has it as long as the player specifies he wants it? I don't recall seeing a cyber gill until SR3 and then it wasn't grouped with Air filtration systems.

SR2 repeats the description from SR1 so nothing additional there. SR3 removed the part with the artificial gill, had they already planned the cyber gill from Cyberpirates you mentioned??

My interpretation of the artificial gill as a specialised form of the air filter would be that it's acquired specifically for that role though I can't tell what the rating would mean.

Filters and the cyber gill seem a bit expensive in essence considering they basically replace cheap kit like gas masks or the non cyber gill, though perhaps the ingested toxin filter isn't so redundant in light of recent happenings.