An exhaust system is usually piping used to guide reaction exhaust gases away from a controlled combustion inside an engine. The entire system conveys burnt gases from the engine and includes one or more exhaust pipes. Depending on the overall system design, the exhaust gas may flow through one or more of:

Cylinder head (header) and exhaust manifold or extractor.
A turbocharger to increase engine power.
A catalytic converter to reduce air pollution.
A muffler (North America) / silencer(UK/India), to reduce noise.

An exhaust pipe must be carefully designed to carry toxic and/or noxious gases away from the machine/engine. The gases from most types of machines are very hot; the pipe must be heat-resistant, and it must not pass through or near anything that can burn or can be damaged by heat. A chimney serves as an exhaust pipe in a stationary structure. For the internal combustion engine it is important to have the exhaust system “tuned” (refer to tuned exhaust) for optimal efficiency.