chimney stack vs exhaust pipe

chimney stack

noun
  • A vertical structure, normally of brick, rising from a roof, containing one or more flues, each one terminating in a chimney pot. 

exhaust pipe

noun
  • For internal combustion engines, the pipe that vents waste gases from the engine. 

  • On a steam locomotive, a pipe which takes away steam exhausted from a cylinder. 

How often have the words chimney stack and exhaust pipe occurred in a corpus of books? (source: Google Ngram Viewer )