▁and ▁returned ▁to ▁the ▁deck ▁or ▁qu ays ide . ▁▁ ▁A ▁wet ▁bell , ▁or ▁open ▁bell , ▁is ▁similar ▁to ▁a ▁div ing ▁stage ▁in ▁concept , ▁but ▁has ▁an ▁air ▁space , ▁open ▁to ▁the ▁water ▁at ▁the ▁bottom ▁in ▁which ▁the ▁divers , ▁or ▁at ▁least ▁their ▁heads , ▁can ▁shelter ▁during ▁as cent ▁and ▁descent . ▁ ▁Prov iding ▁g ases ▁to ▁acceler ate ▁decom pression ▁▁ ▁Red uc ing ▁the ▁partial ▁pressure ▁of ▁the ▁in ert ▁gas ▁component ▁of ▁the ▁breath ing ▁mixture ▁will ▁acceler ate ▁decom pression ▁as ▁the ▁concentration ▁gradient ▁will ▁be ▁greater ▁for ▁a ▁given ▁depth . ▁This ▁is ▁usually ▁achieved ▁by ▁increasing ▁the ▁partial ▁pressure ▁of ▁o xygen ▁in ▁the ▁breath ing ▁gas , ▁as ▁subst itut ing ▁a ▁different ▁in ert ▁gas ▁may ▁have ▁counter - diff usion ▁comp lications ▁due ▁to ▁differ ing ▁rates ▁of ▁diffusion , ▁which ▁can ▁lead ▁to ▁a ▁net ▁gain ▁in ▁total ▁dissol ved ▁gas ▁t ension ▁in ▁a ▁t issue . ▁This ▁can ▁lead ▁to ▁b ubble ▁formation ▁and ▁growth , ▁with ▁decom pression ▁sick ness ▁as ▁a ▁consequence . ▁Part ial ▁pressure ▁of ▁o xygen ▁is ▁usually ▁limited ▁to ▁ 1 . 6 ▁bar ▁during ▁in ▁water ▁decom pression ▁for ▁sc uba ▁divers , ▁but ▁can ▁be ▁up ▁to ▁ 1 . 9 ▁bar ▁in - water ▁and ▁ 2 . 2 ▁bar ▁in ▁the ▁chamber ▁when ▁using ▁the ▁US ▁Navy ▁tables ▁for ▁surface ▁decom pression . ▁ ▁Stage ▁cyl ind ers ▁are ▁cyl ind