▁be ▁referred ▁to ▁as ▁" deep ▁air " ▁courses , ▁but ▁are ▁now ▁commonly ▁called ▁" ext ended ▁range " ▁courses . ▁The ▁ 1 3 0   ft ▁limit ▁entered ▁the ▁recre ation ▁and ▁technical ▁communities ▁in ▁the ▁USA ▁from ▁the ▁military ▁div ing ▁community ▁where ▁it ▁was ▁the ▁depth ▁at ▁which ▁the ▁US ▁Navy ▁recommended ▁sh ifting ▁from ▁sc uba ▁to ▁surface ▁supplied ▁air . ▁The ▁scientific ▁div ing ▁community ▁has ▁never ▁specified ▁a ▁ 1 3 0 - foot ▁limit ▁in ▁its ▁protocol s ▁and ▁has ▁never ▁experienced ▁any ▁acc idents ▁or ▁inj uries ▁during ▁air ▁div es ▁between ▁ 1 3 0 ▁feet ▁and ▁the ▁deep est ▁air ▁div es ▁that ▁the ▁scientific ▁div ing ▁community ▁perm its , ▁ 1 9 0 ▁feet , ▁where ▁the ▁U . S . ▁Navy ▁Standard ▁Air ▁T ables ▁sh ifts ▁to ▁the ▁Exception al ▁Ex pos ure ▁T ables . ▁In ▁Europe ▁some ▁countries ▁set ▁the ▁recre ational ▁div ing ▁limit ▁at ▁, ▁and ▁that ▁corresponds ▁with ▁the ▁limit ▁also ▁im posed ▁in ▁some ▁professional ▁fields , ▁such ▁as ▁police ▁divers ▁in ▁the ▁UK . ▁The ▁major ▁French ▁ag encies ▁all ▁teach ▁div ing ▁on ▁air ▁to ▁ ▁as ▁part ▁of ▁their ▁standard ▁recre ational ▁cert ifications . ▁ ▁Deep ▁air ▁pro ponents ▁base ▁the ▁depth ▁limit ▁of ▁air ▁div ing ▁upon ▁the ▁risk ▁of ▁o xygen ▁to x icity . ▁According ly , ▁they ▁view ▁the ▁limit ▁as ▁being ▁the ▁depth ▁at ▁which ▁partial ▁pressure ▁of ▁o xygen ▁reaches ▁