service staff vs maintenance staff

service staff and maintenance staff both are nouns.

Word	Noun	Adjective	Verb	Adverb
service staff	Yes	No	No	No
maintenance staff	Yes	No	No	No

As nouns, service staff and maintenance staff are synonyms defined as:

service staff and maintenance staff: those in a business responsible for maintaining the physical plant

service staff (noun)	maintenance staff (noun)
those in a business responsible for maintaining the physical plant	those in a business responsible for maintaining the physical plant