I'd be interested in who started using one to help with the weight of the brick they call a bov. As for history well you know what some say about knowing it or not .
I only worry about co2 when it's combined with high po2. Heavy breathing I leave to you and your Vicker.
IV not seen a increase in divers having co2 hits or being saved by buddy s.
In fact IV read about CCR divers passing away right in sight of their fellow gurus all sat watching .
Not sure if a gag was in use or not .