▁gas ▁which ▁was ▁cached ▁to ▁be ▁picked ▁up ▁later ; ▁ ▁The ▁development ▁of ▁an ▁ins u fficient ▁or ▁excess ive ▁PO 2 ▁in ▁the ▁loop ▁of ▁C CR s ▁and ▁S CR s ; ▁ ▁High ▁CO 2 ▁levels ▁in ▁the ▁breath ing ▁loop ▁of ▁re bre athers ▁due ▁to ▁scr ub ber ▁break through ; ▁ ▁Flo oding ▁of ▁the ▁re bre ather ▁loop ▁rendering ▁it ▁unus able . ▁ ▁Fail ure ▁to ▁control ▁depth . ▁ ▁Fail ure ▁to ▁control ▁depth ▁is ▁critical ▁during ▁decom pression , ▁where ▁the ▁in ability ▁to ▁stay ▁at ▁the ▁correct ▁depth ▁due ▁to ▁excess ive ▁bu oy ancy ▁is ▁associated ▁with ▁a ▁high ▁risk ▁of ▁decom pression ▁sick ness ▁and ▁a ▁raised ▁risk ▁of ▁bar ot ra uma ▁of ▁as cent . ▁There ▁are ▁several ▁ways ▁that ▁excess ive ▁bu oy ancy ▁can ▁be ▁caused , ▁some ▁of ▁which ▁can ▁be ▁managed ▁by ▁the ▁diver ▁if ▁prompt ▁and ▁correct ▁action ▁is ▁taken , ▁and ▁others ▁which ▁cannot ▁be ▁corrected . ▁This ▁problem ▁may ▁be ▁caused ▁by ▁poor ▁planning , ▁in ▁that ▁the ▁diver ▁may ▁under est imate ▁the ▁weight ▁loss ▁of ▁using ▁up ▁the ▁breath ing ▁gas ▁in ▁all ▁the ▁cyl ind ers , ▁by ▁losing ▁ball ast ▁weights ▁during ▁the ▁d ive , ▁or ▁by ▁infl ation ▁problems ▁with ▁bu oy ancy ▁compens ator ▁or ▁dry ▁suit , ▁or ▁both . ▁ ▁In su fficient ▁ball ast ▁weight ▁to ▁allow ▁neutral ▁bu oy ancy ▁at ▁the ▁shall ow est ▁decom pression ▁stop ▁with