At the current state of development, the automobile is primarily a liquid fuel based vehicle. That is, the Auto uses an internal combustion engine that compresses a vaporized, liquid fuel for ignition, then ignites it with an electrical spark. That spark causes an explosion that drives the piston, turns the crankshaft and starts the cycle for another cylinder. After the fuel is burnt, it is passed into the exhaust system to be released outside of the vehicle. For the safety of any passengers and the vehicle's driver, the exhaust should release the fumes at the rear of the automobile and away from the passenger area.
The problem with this system is the chemicals that are released by the combustion of petroleum based fuels, the most common of which is carbon monoxide. To ensure the gases are a bit less harmful, the Exhaust system has a feature known as the Catalytic Converter. This simple device was first developed in the mid seventies as a way to meet government regulations. It handles this task surprisingly well. The catalytic converter functions by filtering the exhaust fumes through one or more catalyzing agents. These are typically platinum, but others may include rhodium and palladium.
The primary functions of the catalytic converter are to channel the exhaust past the catalyst and to provide the largest surface space of catalyzing materials. This is usually handled by placing a ceramic container coated with the catalyzing material inside the converter. There are typically two catalysts used in each converter. The first is the oxidizing catalyst and the second is the reduction catalyst. The purpose of reduction is the change or convert the molecule into a more harmless form.
Methods for filtering the exhaust through a catalyst use either a honeycomb shaped filtration system or ceramic beads coated with the material. The typical automobile uses the honeycomb method. This solution provides the best coverage for the volume of exhaust treated without restricting the exhaust flow. This is important with many modern vehicles because holding the exhaust too long could cause performance problems, but failing to treat it properly will definitely result in too many Vehicle emissions.