▁process . ▁The ▁rate ▁of ▁decom pression ▁typically ▁ranges ▁between ▁ 3 ▁and ▁ 6   f sw ▁( 0 . 9 ▁and ▁ 1 . 8   ms w ) ▁per ▁hour . ▁ ▁The ▁US ▁Navy ▁Hel io x ▁s atur ation ▁decom pression ▁rates ▁require ▁a ▁partial ▁pressure ▁of ▁o xygen ▁to ▁be ▁maintained ▁at ▁between ▁ 0 . 4 4 ▁and ▁ 0 . 4 8   ▁at m ▁when ▁possible , ▁but ▁not ▁to ▁exceed ▁ 2 3 % ▁by ▁volume , ▁to ▁restrict ▁the ▁risk ▁of ▁fire . ▁For ▁practical ity ▁the ▁decom pression ▁is ▁done ▁in ▁incre ments ▁of ▁ 1   f sw ▁at ▁a ▁rate ▁not ▁exceed ing ▁ 1   f sw ▁per ▁minute , ▁followed ▁by ▁a ▁stop , ▁with ▁the ▁average ▁comp lying ▁with ▁the ▁table ▁as cent ▁rate . ▁De com pression ▁is ▁done ▁for ▁ 1 6 ▁hours ▁in ▁ 2 4 , ▁with ▁the ▁remaining ▁ 8 ▁hours ▁split ▁into ▁two ▁rest ▁periods . ▁A ▁further ▁adaptation ▁generally ▁made ▁to ▁the ▁schedule ▁is ▁to ▁stop ▁at ▁ 4   f sw ▁for ▁the ▁time ▁that ▁it ▁would ▁theoret ically ▁take ▁to ▁complete ▁the ▁decom pression ▁at ▁the ▁specified ▁rate , ▁i . e . ▁ 8 0 ▁minutes , ▁and ▁then ▁complete ▁the ▁decom pression ▁to ▁surface ▁at ▁ 1   f sw ▁per ▁minute . ▁This ▁is ▁done ▁to ▁avoid ▁the ▁possibility ▁of ▁losing ▁the ▁door ▁se al ▁at ▁a ▁low ▁pressure ▁differential ▁and ▁losing ▁the ▁last