smokeshaft vs ventilator

smokeshaft

ventilator

noun
  • A machine that moves breathable air into and out of the lungs of a patient who is unable to breathe sufficiently. 

  • A device that circulates fresh air and expels stale or noxious air. 

  • Some behaviour or happening that relieves a tense atmosphere or situation. 

How often have the words smokeshaft and ventilator occurred in a corpus of books? (source: Google Ngram Viewer )