How is scrubber exhaustion measured?

[Tracy]

One wonders if CE approval's improved or hindered rebreather design.

Yes. It definitely did those things.

 

[Akimbo]

In essence the latest generation of rebreathers are built upon decades of research and refinements: truly standing on the shoulders of giants.

Agreed. There was an enormous amount of hope and anticipation in recreational diving when the Electrolung came out in 1968, until a well known diver was killed. This article in Skin Diver Magazine was typical. This is where Bob Hollis caught the "Rebreather Bug". It was the motivation behind a lot of rebreather work, mostly focused on military applications.