escape valve vs relief valve

escape valve and relief valve both are nouns.

Word	Noun	Adjective	Verb	Adverb
escape valve	Yes	No	No	No
relief valve	Yes	No	No	No

As nouns, escape valve and relief valve are synonyms defined as:

escape valve and relief valve: a valve in a container in which pressure can build up (as a steam boiler); it opens automatically when the pressure reaches a dangerous level

Other synonyms of escape valve include escape, escape cock, safety valve.

escape valve (noun)	relief valve (noun)
a valve in a container in which pressure can build up (as a steam boiler); it opens automatically when the pressure reaches a dangerous level	a valve in a container in which pressure can build up (as a steam boiler); it opens automatically when the pressure reaches a dangerous level