chemical toilet vs small room

chemical toilet

noun
  • A toilet or chamber pot which treats waste in place with chemical disinfectants and deodorizers, as in airplane lavatories. 

small room

noun
  • A lavatory: a room intended for urination and defecation. 

  • Used other than figuratively or idiomatically: see small, room. 

How often have the words chemical toilet and small room occurred in a corpus of books? (source: Google Ngram Viewer )