sprinkler head vs vaporizer

sprinkler head

noun
  • A heat-activated device that sprays water in the event of a fire, usually mounted on a ceiling. 

vaporizer

noun
  • A device with a heating element, used to vaporize a liquid. 

  • A device with a heating element, used to vaporize a liquid solution with medicine. The produced vapor condensates into fine aerosols, forming a mist inside the device, to be inhaled by the patient for delivery of the medicine into the lungs. 

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