▁of ▁man aging ▁a ▁variety ▁of ▁breath ing ▁mi xt ures ▁introdu ces ▁other ▁ris ks ▁and ▁is ▁managed ▁by ▁equipment ▁configuration ▁and ▁proced ural ▁training . ▁To ▁reduce ▁nit ro gen ▁nar cos is , ▁it ▁is ▁common ▁to ▁use ▁trim ix ▁which ▁uses ▁hel ium ▁to ▁replace ▁some ▁of ▁the ▁nit ro gen ▁in ▁the ▁diver ' s ▁breath ing ▁mixture , ▁or ▁hel io x , ▁in ▁which ▁there ▁is ▁no ▁nit ro gen . ▁ ▁In ability ▁to ▁asc end ▁directly ▁Techn ical ▁div es ▁may ▁altern atively ▁be ▁defined ▁as ▁div es ▁where ▁the ▁diver ▁cannot ▁safely ▁asc end ▁directly ▁to ▁the ▁surface ▁either ▁due ▁to ▁a ▁mand atory ▁decom pression ▁stop ▁or ▁a ▁physical ▁ce iling . ▁This ▁form ▁of ▁div ing ▁implies ▁a ▁much ▁larger ▁reli ance ▁on ▁redund ancy ▁of ▁critical ▁equipment ▁and ▁proced ural ▁training ▁since ▁the ▁diver ▁must ▁stay ▁under water ▁until ▁it ▁is ▁safe ▁to ▁asc end ▁or ▁the ▁diver ▁has ▁successfully ▁ex ited ▁the ▁overhead ▁environment . ▁ ▁De com pression ▁stops ▁ ▁A ▁diver ▁at ▁the ▁end ▁of ▁a ▁long ▁or ▁deep ▁d ive ▁may ▁need ▁to ▁do ▁decom pression ▁stops ▁to ▁avoid ▁decom pression ▁sick ness , ▁also ▁known ▁as ▁" the ▁b ends ". ▁Met abol ically ▁in ert ▁g ases ▁in ▁the ▁diver ' s ▁breath ing ▁gas , ▁such ▁as ▁nit ro gen ▁and ▁hel ium , ▁are ▁absor bed ▁into ▁body ▁t issues ▁when ▁bre athed ▁under ▁high ▁pressure , ▁mainly ▁during ▁the ▁deep ▁phase