They are operated by a control on the dash, either manually or automatically. The air pump pumps compressed air into the exhaust manifold and in a few cases to the catalytic converter. A belt from the engine drives the air pump. Here, the air is compressed and sent off to the exhaust manifold where it speeds up the emissions burning process. Stainless steel nozzles are used to shoot the air into the exhaust manifold, because they will not burn.
Some engines use a pulse air injection system.
Pulses of exhaust gases are used by the system to operate an air pump that delivers air into the exhaust system. The chief source of power of the electrical system is the alternating-current generator, or alternator. Its shaft is driven by the same belt that spins the fan and it keeps the engine running. It converts mechanical energy into alternating-current electricity, which is then channeled through diodes that alter it to direct current for the electrical system and for recharging the battery. The gauge should dip when the engine is started, then go up as the alternator re- charges the battery.