gas pressure vs pressure level

gas pressure and pressure level both are nouns.

Word	Noun	Adjective	Verb	Adverb
gas pressure	Yes	No	No	No
pressure level	Yes	No	No	No

As nouns, pressure level is a hypernym of gas pressure; that is, pressure level is a word with a broader meaning than gas pressure:

gas pressure: the pressure exerted by a gas
pressure level: the force applied to a unit area of surface; measured in pascals (SI unit) or in dynes (cgs unit)

Other hypernyms of gas pressure include force per unit area, pressure.

gas pressure (noun)	pressure level (noun)
the pressure exerted by a gas	the force applied to a unit area of surface; measured in pascals (SI unit) or in dynes (cgs unit)