▁environment ▁up ▁to ▁ 2 ▁metres ▁away ▁ ▁use ▁of ▁a ▁warm ▁air ▁hand ▁dry er ▁spread ▁micro - organ isms ▁up ▁to ▁ 0 . 2 5 ▁metres ▁from ▁the ▁dry er ▁ ▁paper ▁to w els ▁showed ▁no ▁significant ▁spread ▁of ▁micro - organ isms . ▁ ▁In ▁ 2 0 0 5 , ▁in ▁a ▁study ▁conducted ▁by ▁T U V ▁Produ kt ▁und ▁Um welt , ▁different ▁hand ▁dry ing ▁methods ▁were ▁evaluated . ▁The ▁following ▁changes ▁in ▁the ▁b acter ial ▁count ▁after ▁dry ing ▁the ▁hands ▁were ▁observed : ▁ ▁Ster il ization ▁Ster il ization ▁ ▁is ▁a ▁process ▁intended ▁to ▁kill ▁all ▁micro organ isms ▁and ▁is ▁the ▁highest ▁level ▁of ▁micro b ial ▁kill ▁that ▁is ▁possible . ▁Ster il izers ▁may ▁be ▁heat ▁only , ▁steam , ▁or ▁liquid ▁chemical . ▁Effect iveness ▁of ▁the ▁ster il izer , ▁for ▁example ▁a ▁steam ▁aut oc lave ▁is ▁determined ▁in ▁three ▁ways . ▁First , ▁mechanical ▁indic ators ▁and ▁gau ges ▁on ▁the ▁machine ▁itself ▁indicate ▁proper ▁operation ▁of ▁the ▁machine . ▁Second ▁heat ▁sensitive ▁indic ators ▁or ▁t ape ▁on ▁the ▁ster il izing ▁b ags ▁change ▁color ▁which ▁indicate ▁proper ▁levels ▁of ▁heat ▁or ▁steam . ▁And , ▁third ▁( most ▁important ly ) ▁is ▁bi ological ▁testing ▁in ▁which ▁a ▁micro organ ism ▁that ▁is ▁highly ▁heat ▁and ▁chemical ▁resist ant ▁( o ften ▁the ▁b acter ial ▁end osp ore ) ▁is ▁selected ▁as ▁the ▁standard ▁challenge . ▁If ▁the