respirator vs breathing device

respirator and breathing device both are nouns.

Word	Noun	Adjective	Verb	Adverb
respirator	Yes	No	No	No
breathing device	Yes	No	No	No

As nouns, breathing device is a hypernym of respirator; that is, breathing device is a word with a broader meaning than respirator:

respirator: a breathing device for administering long-term artificial respiration
breathing device: a device that facilitates breathing in cases of respiratory failure

Other hypernyms of respirator include breathing apparatus, breathing machine, ventilator.

respirator (noun)	breathing device (noun)
a breathing device for administering long-term artificial respiration	a device that facilitates breathing in cases of respiratory failure
a protective mask with a filter; protects the face and lungs against poisonous gases