Posted by Kendall Raine on March 05, 2002 at 12:19:03:
In Reply to: Buhlman versus RGBM posted by Oceanbobber on March 05, 2002 at 09:12:21:
OK. Really simple. Anyone who tees off on me for being too simplistic is really gonna get it
:-). Buhlmann assumes inert gas remains in solution until it reaches a critical tension wherein bubbles are created. This is known as the dissolved gas model. Buhlmann models attempt to deal with the dissolved phase by bringing you up to a point just below the critical tension level. As such, deco profiles tend to involve short intermediate depth stops and long shallow stops. RGBM assumes bubble seeds pre-exist in solution and are excited at much lower tensions during decompression. RGBM recognises that decompression is a balancing act between eliminated free phase bubbles deep and dissolved gas shallow. As such, RGBM attempts to shrink and eliminate free phase bubbles during decompression by slowing the ascent rate early(i.e. doing deep stops)while using shallow stops to take care of the dissolved gas issue. RGBM deco schedulues tend to start deco much deeper than Buhlmann. For trimix dives, these stops can start as deep as 4/5 of bottom depth. The deep stops are short. Intermediate stops are generally longer than Buhlmann stops while the shallow stops are generally shorter than the Buhlmann stops. For trimix dives, RGBM actually generates tables which can have a shorter overall deco time than Buhmann. This assumes the correct deco gasses are used. This is the sledgehammer explanation and there's a lot more to it if you want to go there.