▁transport ation ▁of ▁products ▁is ▁by ▁sh ipping ▁liquid ▁product ▁for ▁large ▁quantities ▁or ▁as ▁de war ▁flask s ▁or ▁gas ▁cyl ind ers ▁for ▁small ▁quantities . ▁ ▁Non - c ry ogen ic ▁processes ▁▁ ▁Press ure ▁swing ▁ad s or ption ▁provides ▁separation ▁of ▁o xygen ▁or ▁nit ro gen ▁from ▁air ▁without ▁li que f action . ▁The ▁process ▁oper ates ▁around ▁ambient ▁temperature ; ▁a ▁ze ol ite ▁( m ole cular ▁sp on ge ) ▁is ▁exposed ▁to ▁high ▁pressure ▁air , ▁then ▁the ▁air ▁is ▁released ▁and ▁an ▁ad s or bed ▁film ▁of ▁the ▁desired ▁gas ▁is ▁released . ▁The ▁size ▁of ▁compress or ▁is ▁much ▁reduced ▁over ▁a ▁li que f action ▁plant , ▁and ▁port able ▁o xygen ▁concent rat ors ▁are ▁made ▁in ▁this ▁manner ▁to ▁provide ▁o xygen - en rich ed ▁air ▁for ▁medical ▁purposes . ▁V acu um ▁swing ▁ad s or ption ▁is ▁a ▁similar ▁process ; ▁the ▁product ▁gas ▁is ▁evol ved ▁from ▁the ▁ze ol ite ▁at ▁sub - at mos pher ic ▁pressure . ▁ ▁M emb rane ▁techn ologies ▁can ▁provide ▁alternate , ▁lower - energy ▁approaches ▁to ▁air ▁separation . ▁For ▁example , ▁a ▁number ▁of ▁approaches ▁are ▁being ▁expl ored ▁for ▁o xygen ▁generation . ▁Pol ym er ic ▁memb ran es ▁operating ▁at ▁ambient ▁or ▁warm ▁temper atures , ▁for ▁example , ▁may ▁be ▁able ▁to ▁produce ▁o xygen - en rich ed ▁air ▁( 2 5 - 5 0 %