ases ▁on ▁the ▁body ▁during ▁a ▁d ive ▁and ▁additional ▁skills ▁are ▁needed ▁to ▁safely ▁manage ▁their ▁use . ▁ ▁Deep ▁air / ext ended ▁range ▁div ing ▁One ▁of ▁the ▁more ▁divis ive ▁subjects ▁in ▁technical ▁div ing ▁concerns ▁using ▁com pressed ▁air ▁as ▁a ▁breath ing ▁gas ▁on ▁div es ▁below ▁. ▁Some ▁training ▁ag encies ▁still ▁promote ▁and ▁teach ▁courses ▁using ▁air ▁up ▁to ▁depth s ▁of ▁ 6 0 m . ▁These ▁include ▁T DI , ▁I ANT D ▁and ▁D S AT / P AD I . ▁O thers , ▁including ▁NA UI ▁T ec , ▁G UE , ▁I SE ▁and ▁U TD ▁consider ▁that ▁div ing ▁deeper ▁than ▁, ▁depending ▁upon ▁ag ency , ▁on ▁air ▁is ▁un accept ably ▁ris ky . ▁They ▁promote ▁the ▁use ▁of ▁mi xt ures ▁containing ▁hel ium ▁to ▁limit ▁the ▁apparent ▁n arc otic ▁depth ▁to ▁their ▁ag ency ▁specified ▁limit ▁should ▁be ▁used ▁for ▁div es ▁beyond ▁a ▁certain ▁limit . ▁Even ▁though ▁T DI ▁and ▁I ANT D ▁teach ▁courses ▁using ▁air ▁up ▁to ▁depth s ▁of ▁ 6 0 m , ▁they ▁also ▁offer ▁courses ▁include ▁" hel it ro x " ▁" re cre ational ▁trim ix " ▁and ▁" adv ance ▁recre ational ▁trim ix " ▁that ▁also ▁use ▁mi xt ures ▁containing ▁hel ium ▁to ▁mit ig ate ▁n arc otic ▁concerns ▁when ▁the ▁div ing ▁depth ▁is ▁limited ▁to ▁ 3 0 - 4 5 m . ▁ ▁Such ▁courses ▁used ▁to