The air-injection or AIR system is an exhaust-emission-control system that uses a low-pressure pump to inject fresh air into the exhaust system. It reduces hydrocarbons and carbon monoxide emissions by injecting fresh air into the exhaust gases after leaving the combustion chamber. The air causes the unburned and partially burned fuel to continue burning. This system reduces the amount of these pollutants and helps convert them into carbon dioxide and water. The air enters the exhaust manifold through the nozzles positioned opposite the exhaust ports. When the air hits the hot exhaust gas coming from the exhaust port, much of the hydrocarbons and carbon monoxide changes into water and carbon dioxide. The air-injection system requires no routine service except to replace the air filter if specified in the maintenance schedule. Most air pumps have a centrifugal filter which requires no service, so check the air-pump drive belt periodically for tension and wear.