▁the ▁other ▁hand , ▁dry ▁heat ▁ster il ization , ▁which ▁is ▁performed ▁with ▁the ▁help ▁of ▁an ▁o ven , ▁is ▁also ▁an ▁accessible ▁type ▁of ▁ster il ization , ▁although ▁it ▁can ▁only ▁be ▁used ▁to ▁dis in fect ▁instruments ▁that ▁are ▁made ▁of ▁metal ▁or ▁glass . ▁The ▁very ▁high ▁temper atures ▁needed ▁to ▁perform ▁ster il ization ▁in ▁this ▁way ▁are ▁able ▁to ▁m elt ▁the ▁instruments ▁that ▁are ▁not ▁made ▁of ▁glass ▁or ▁metal . ▁ ▁Ste am ▁ster il ization ▁is ▁done ▁at ▁a ▁temperature ▁of ▁ 1 2 1 ▁C ▁( 2 5 0 ▁F ) ▁with ▁a ▁pressure ▁of ▁ 2 0 9 ▁k Pa ▁( 1 5   l bs / in 2 ). ▁In ▁these ▁conditions , ▁rub ber ▁items ▁must ▁be ▁ster il ized ▁for ▁ 2 0 ▁minutes , ▁and ▁wrapped ▁items ▁ 1 3 4 ▁C ▁with ▁pressure ▁of ▁ 3 1 0 ▁k Pa ▁for ▁ 7 ▁minutes . ▁The ▁time ▁is ▁counted ▁once ▁the ▁temperature ▁that ▁is ▁needed ▁has ▁been ▁reached . ▁Ste am ▁ster il ization ▁requires ▁four ▁conditions ▁in ▁order ▁to ▁be ▁efficient : ▁ade qu ate ▁contact , ▁sufficiently ▁high ▁temperature , ▁correct ▁time ▁and ▁sufficient ▁mo ist ure . ▁Ster il ization ▁using ▁steam ▁can ▁also ▁be ▁done ▁at ▁a ▁temperature ▁of ▁ 1 3 2 ▁C ▁( 2 7 0 ▁F ), ▁at ▁a ▁double ▁pressure . ▁D ry ▁heat ▁ster il ization ▁is ▁performed ▁at ▁ 1 7 0 ▁C ▁( 3