As nouns the difference between air and tephra
is that
air is (uncountable|historical|astrology|alchemy|science) the atmospheric substance above the surface of the earth which animals breathe, formerly considered to be a single substance, one of the four basic elements of ancient philosophy and one of the five basic elements of eastern traditions while
tephra is (geology) the solid material thrown into the air by a volcanic eruption that settles on the surrounding areas.
As a verb air
is to bring (something) into contact with the air, so as to freshen or dry it.