An exhaust pipe is usually a pipe used to guide waste exhaust gases away from a controlled combustion inside an engine or stove.

An exhaust pipe must be carefully designed to carry toxic and/or noxious gases away from the users of the machine. Indoor generators and furnaces can quickly fill an enclosed space with carbon monoxide or other poisonous exhaust if they are not properly vented to the outdoors. Also, the exhaust gases from most types of machine are very hot; the pipe must be heat-resistant, and it must not pass through or near any combustible materials.

An automobile's exhaust system usually connects to the exhaust manifold and usually includes a muffler (UK: silencer) to reduce engine noise, and often in recent years a catalytic converter to reduce the emissions that contribute to air pollution.

See also: Automobile emissions control

In a two-stroke engine, such as that used on dirt bikes, a bulge in the exhaust pipe known as an expansion chamber uses the pressure of the exhaust to create a pump that squeezes more air and fuel into the cylinder during the intake stroke. This provides greater power and fuel efficiency: see this link (http://science.howstuffworks.com//two-stroke.htm)

A chimney serves a similar function in a stationary structure.