Your car may be equipped with a system that reduces exhaust fumes by mixing air with the exhaust to help dilute potentially harmful substances. It's known as an air injector reaction system. When gasoline or other fuel is burned in an internal combustion engine, some of the fuel fails to ignite, resulting in the formation of carbon monoxide. When additional air is mixed with unburned fuel, it may have a better chance of fully combusting and thereby reducing emissions. In some systems, the air is injected directly into the manifold of the engine. In others, air is pumped into the exhaust pipes near the catalytic converter. Since catalytic converters rely on oxygen to work properly, air injection systems may help them function more efficiently. Contact a qualified mechanic for more information on air injection systems.