Exhaust system Law in the United States and other countries to not have a catalytic converter. Converters may not be removed from a vehicle that is used only for "off-road" driving in the United States. The main purpose of a catalytic converter on an automobile is to reduce harmful emissions of hydrocarbons, carbon monoxide and nitrogen oxides into the atmosphere. They work by transforming the polluted exhaust components into water and carbon dioxide. Cat-back (also cat back and catback) refers to the portion of the exhaust system from the outlet of the catalytic converter to the final vent to open air. This
Exhaust system are not properly vented to the outdoors. Also, 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. Also this should meet the regulation norms maintained in each country. In China, China 5; In European countries, EURO 5; In India, BS-4, etc., In most motorcycles