snorkel breather vs air passage

snorkel breather and air passage both are nouns.

Word	Noun	Adjective	Verb	Adverb
snorkel breather	Yes	No	No	No
air passage	Yes	No	No	No

As nouns, air passage is a hypernym of snorkel breather; that is, air passage is a word with a broader meaning than snorkel breather:

snorkel breather: air passage provided by a retractable device containing intake and exhaust pipes; permits a submarine to stay submerged for extended periods of time
air passage: a duct that provides ventilation (as in mines)

Other hypernyms of snorkel breather include air duct, airway.

snorkel breather (noun)	air passage (noun)
air passage provided by a retractable device containing intake and exhaust pipes; permits a submarine to stay submerged for extended periods of time	a duct that provides ventilation (as in mines)