exhaust chimney; stack; flue
Refers to a duct or pipe for discharging exhaust gases, smoke, or fumes from engines, factories, or heating systems.
White smoke is coming out of the factory's exhaust chimney.
Please inspect the boiler flue regularly.
気筒 refers to the combustion chamber inside an engine, while 排気筒 refers to the exhaust pipe or flue that carries gases away, despite sharing the 筒 character.
Compound of 排気 (exhaust) + 筒 (pipe, cylinder).