Chimney (locomotive)

Great Western locomotives with their distinctive copper-rimmed chimneys
The new-build steam locomotive Leviathan, a 4-4-0 with a large spark-arresting chimney

The chimney (smokestack or stack in American and Canadian English) is the part of a steam locomotive through which smoke leaves the boiler. As well, steam locomotive exhaust systems typically vent cylinder steam exhaust through the chimney, to enhance the draught through the boiler. Chimneys are designed to carry the exhaust steam and smoke clear of the driver's line of sight while remaining short enough to clear overhead structures. Some chimneys included apparatus to suppress the dispersal of sparks.