▁switch . ▁An ▁error ▁of ▁selection ▁could ▁comprom ise ▁the ▁decom pression , ▁or ▁result ▁in ▁a ▁loss ▁of ▁conscious ness ▁due ▁to ▁o xygen ▁to x icity . ▁ ▁The ▁diver ▁is ▁faced ▁with ▁a ▁problem ▁of ▁optim ising ▁for ▁gas ▁volume ▁carried , ▁number ▁of ▁different ▁g ases ▁carried , ▁depth s ▁at ▁which ▁switch es ▁can ▁be ▁made , ▁bottom ▁time , ▁decom pression ▁time , ▁g ases ▁available ▁for ▁emer gency ▁use , ▁and ▁at ▁which ▁depth s ▁they ▁become ▁available , ▁both ▁for ▁them self ▁and ▁other ▁members ▁of ▁the ▁team , ▁while ▁using ▁available ▁cyl ind ers ▁and ▁remaining ▁able ▁to ▁manage ▁the ▁cyl ind ers ▁during ▁the ▁d ive . ▁This ▁problem ▁can ▁be ▁simplified ▁if ▁st aging ▁the ▁cyl ind ers ▁is ▁possible . ▁This ▁is ▁the ▁practice ▁of ▁leaving ▁a ▁cyl inder ▁at ▁a ▁point ▁on ▁the ▁return ▁route ▁where ▁it ▁can ▁be ▁picked ▁up ▁and ▁used , ▁possibly ▁depos iting ▁the ▁previously ▁used ▁cyl inder , ▁which ▁will ▁be ▁retrieved ▁later , ▁or ▁having ▁a ▁support ▁diver ▁supply ▁additional ▁gas . ▁These ▁strateg ies ▁rely ▁on ▁the ▁diver ▁being ▁reli ably ▁able ▁to ▁get ▁to ▁the ▁st aged ▁gas ▁supply . ▁The ▁st aged ▁cyl ind ers ▁are ▁usually ▁cli pped ▁off ▁to ▁the ▁distance ▁line ▁or ▁shot line ▁to ▁make ▁them ▁easier ▁to ▁find . ▁ ▁Management ▁of ▁multiple ▁cyl ind ers ▁When ▁multiple ▁cyl ind ers ▁containing ▁different ▁gas ▁mi xt ures ▁are ▁carried , ▁the ▁diver ▁must ▁ensure ▁that ▁the