... although (probably) perfectly adequate from an engineering point of view!
The first attempt at AGSS that I saw (early 1980's) was simply familiar corrugated black rubber tubing from the anaesthesia machine to a spigot (at about 18'' FFL) on a stainless panel on the theatre wall which led directly into the HVAC exhaust duct. I'm not sure where the duct led ... possibly to atmosphere (as HEPA filtering would presumably have been on the inlet side into theatres). Probably OK (for that period), but I recall that the suction at the spigot was almost imperceptible. Rather like the idea mentioned (but for PES) in the original post!
Later we saw a few "passive" systems; filter cannisters hanging off the anaesthesia machines.
