machine room vs plant room

machine room

noun
  • A limited-access room in a larger building dedicated to HVAC equipment and other machinery. 

  • A dedicated room for computers and related data processing equipment, often having a raised floor, abundant and dedicated air conditioning, and specialized power supply and fire suppression systems. 

plant room

noun
  • A room used to house large machinery (plant), such as air-conditioning equipment. 

  • A room used to grow plants. 

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