fire sprinkler vs sprinkler head

fire sprinkler

noun

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

sprinkler head

noun

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

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