▁tables , ▁it ▁is ▁considered ▁complete ▁after ▁ 1 2 ▁hours , ▁The ▁US ▁Navy ▁ 2 0 0 8 ▁Air ▁tables ▁specify ▁up ▁to ▁ 1 6 ▁hours ▁for ▁normal ▁expos ure . ▁but ▁other ▁algorithms ▁may ▁require ▁more ▁than ▁ 2 4 ▁hours ▁to ▁assume ▁full ▁equilibrium . ▁ ▁Res id ual ▁nit ro gen ▁time ▁ ▁For ▁the ▁planned ▁depth ▁of ▁the ▁repet itive ▁d ive , ▁a ▁bottom ▁time ▁can ▁be ▁calculated ▁using ▁the ▁relevant ▁algorithm ▁which ▁will ▁provide ▁an ▁equivalent ▁gas ▁loading ▁to ▁the ▁resid ual ▁gas ▁after ▁the ▁surface ▁interval . ▁This ▁is ▁called ▁" res id ual ▁nit ro gen ▁time " ▁( R NT ) ▁when ▁the ▁gas ▁is ▁nit ro gen . ▁The ▁R NT ▁is ▁added ▁to ▁the ▁planned ▁" actual ▁bottom ▁time " ▁( AB T ) ▁to ▁give ▁an ▁equivalent ▁" total ▁bottom ▁time " ▁( TB T ) ▁which ▁is ▁used ▁to ▁derive ▁the ▁appropriate ▁decom pression ▁schedule ▁for ▁the ▁planned ▁d ive . ▁ ▁Equ ivalent ▁resid ual ▁times ▁can ▁be ▁derived ▁for ▁other ▁in ert ▁g ases . ▁These ▁calculations ▁are ▁done ▁automatically ▁in ▁personal ▁div ing ▁computers , ▁based ▁on ▁the ▁diver ' s ▁recent ▁div ing ▁history , ▁which ▁is ▁the ▁reason ▁why ▁personal ▁div ing ▁computers ▁should ▁not ▁be ▁shared ▁by ▁divers , ▁and ▁why ▁a ▁diver ▁should ▁not ▁switch ▁computers ▁without ▁a ▁sufficient ▁surface ▁interval ▁( more ▁than ▁ 2 4 ▁hours ▁in ▁most ▁cases , ▁up ▁to ▁ 4 ▁days , ▁depending ▁on