▁gas ▁( us ually ▁air ). ▁▁ ▁A ▁dry ▁bell ▁may ▁be ▁used ▁for ▁b ounce ▁div es ▁to ▁great ▁depth s , ▁and ▁then ▁used ▁as ▁the ▁decom pression ▁chamber ▁during ▁the ▁as cent ▁and ▁later ▁on ▁board ▁the ▁support ▁vessel . ▁In ▁this ▁case ▁it ▁is ▁not ▁always ▁necessary ▁to ▁transfer ▁into ▁a ▁deck ▁chamber , ▁as ▁the ▁bell ▁is ▁quite ▁capable ▁of ▁performing ▁this ▁function , ▁though ▁it ▁would ▁be ▁relatively ▁cr amp ed , ▁as ▁a ▁bell ▁is ▁usually ▁as ▁small ▁as ▁convenient ly ▁possible ▁to ▁minim ize ▁weight ▁for ▁deployment . ▁ ▁A ▁S atur ation ▁System ▁or ▁S atur ation ▁spread ▁typically ▁compr ises ▁a ▁living ▁chamber , ▁transfer ▁chamber ▁and ▁subm ers ible ▁decom pression ▁chamber , ▁which ▁is ▁commonly ▁referred ▁to ▁in ▁commercial ▁div ing ▁as ▁the ▁div ing ▁bell ▁and ▁in ▁military ▁div ing ▁as ▁the ▁personnel ▁transfer ▁caps ule , ▁P TC ▁( Person nel ▁Transfer ▁C aps ule ) ▁or ▁SD C ▁( Sub mers ible ▁De com pression ▁Chamber ). ▁The ▁div ing ▁bell ▁is ▁the ▁elev ator ▁or ▁lift ▁that ▁trans fers ▁divers ▁from ▁the ▁system ▁to ▁the ▁work ▁site ▁and ▁back . ▁At ▁the ▁completion ▁of ▁work ▁or ▁a ▁mission , ▁the ▁s atur ation ▁div ing ▁team ▁is ▁decom pressed ▁gradually ▁back ▁to ▁atmos pher ic ▁pressure ▁by ▁the ▁slow ▁vent ing ▁of ▁system ▁pressure , ▁at ▁rates ▁of ▁about ▁of ▁ ▁to ▁ ▁per ▁day , ▁( sch ed ules ▁vary ). ▁Thus ▁the ▁process ▁involves ▁only