Answer:

oxygen

AnswerCrossword Clue
OXYGENPlants release it
OXYGEN"Inhale" network
OXYGENAbout 21% of air
OXYGENSomething in the air
OXYGENO, in many cases
OXYGENTrendy place to get gas?
OXYGENRoughly 21% of the atmosphere
OXYGENCable television network started by Oprah Winfrey
OXYGENAmbulance tankful
OXYGENIt's in the air
OXYGENStuff in a tent
OXYGENBurning need?
OXYGENScuba gear element
OXYGENSpace station supply
OXYGENGas in the air
OXYGENElement in chlorophyll
OXYGENScuba-tank filler
OXYGENO may stand for it
OXYGENContents of some tents
OXYGENImportant element.
OXYGENType of tent
OXYGENType of mask
OXYGENKind of mask or tent
OXYGENAstronaut's supply
OXYGENAbout 21% of the atmosphere
OXYGENSpace shuttle supply
OXYGENScuba tank content
OXYGENNetwork co-founded by Oprah Winfrey
OXYGENElement in water
OXYGENThe 'O' of H2O
OXYGENPart of H2O
OXYGENKind of mask
OXYGENMost abundant element in the earth's crust
OXYGENMask supply
OXYGENYou can't live without it
OXYGENAstronaut's tankful