The air pollutants released in a car exhaust are due to undesirable chemical reactions inside the engine. The main pollutants are carbon monoxide (CO), unburned hydrocarbon fuel, and nitrogen oxides, which include gases such as nitric oxide (NO) and nitrogen dioxide (NO2). Nitrogen oxides can lead to acid rain, ozone layer depletion, and respiratory health problems.
To prevent these chemicals from being released into the air, cars are equipped with a catalytic converter that breaks down these pollutants before they reach the tailpipe. As a catalytic converter adds additional resistance to the combustion gases moving through the vehicle, its use reduces the engine power and fuel economy. Car manufacturers have developed specially designed high-flow catalytic converters that provide minimal resistance, ensuring that the engine power and fuel economy are not affected too severely.