▁and ▁monitor ▁the ▁decom pression ▁and ▁some ▁mark ▁the ▁under water ▁position ▁of ▁the ▁diver ▁and ▁act ▁as ▁a ▁bu oy ancy ▁control ▁aid ▁and ▁position ▁reference ▁in ▁low ▁visibility ▁or ▁curr ents . ▁De com pression ▁may ▁be ▁short ened ▁( or ▁acceler ated ) ▁by ▁breath ing ▁an ▁o xygen - rich ▁" de co ▁gas " ▁such ▁as ▁a ▁nit ro x ▁with ▁ 5 0 % ▁or ▁more ▁o xygen . ▁The ▁high ▁partial ▁pressure ▁of ▁o xygen ▁in ▁such ▁decom pression ▁mix es ▁create ▁the ▁effect ▁of ▁the ▁o xygen ▁window . ▁This ▁decom pression ▁gas ▁is ▁often ▁carried ▁by ▁sc uba ▁divers ▁in ▁side - sl ung ▁cyl ind ers . ▁C ave ▁divers ▁who ▁can ▁only ▁return ▁by ▁a ▁single ▁route , ▁will ▁often ▁leave ▁decom pression ▁gas ▁cyl ind ers ▁attached ▁to ▁the ▁guid eline ▁at ▁the ▁points ▁where ▁they ▁will ▁be ▁used . ▁Sur face ▁supplied ▁divers ▁will ▁have ▁the ▁composition ▁of ▁the ▁breath ing ▁gas ▁controlled ▁at ▁the ▁gas ▁panel . ▁D ivers ▁with ▁long ▁decom pression ▁oblig ations ▁may ▁be ▁decom pressed ▁inside ▁gas ▁filled ▁ch amb ers ▁in ▁the ▁water ▁or ▁at ▁the ▁surface . ▁ ▁Pl anning ▁and ▁monitoring ▁decom pression ▁▁ ▁Equ ip ment ▁for ▁planning ▁and ▁monitoring ▁decom pression ▁includes ▁decom pression ▁tables , ▁surface ▁computer ▁software ▁and ▁personal ▁decom pression ▁computers . ▁There ▁is ▁a ▁wide ▁range ▁of ▁choice : ▁ ▁A ▁decom pression ▁algorithm ▁is ▁used ▁to ▁calculate ▁the ▁decom pression ▁stops ▁needed ▁for ▁a ▁particular