What are the two main types of emissions control systems?

The two main types of emissions control systems refer to technology designed to reduce the harmful emissions produced by vehicles. Positive Crankcase Ventilation (PCV) and Exhaust Gas Recirculation (EGR) are both critical in this context.

Positive Crankcase Ventilation (PCV) is a system that reroutes gases from the crankcase back into the intake manifold. This process helps to prevent the release of unburned hydrocarbons into the atmosphere, which contributes to air pollution. By allowing these gases to be reintroduced into the combustion process, where they can be burned more thoroughly, PCV systems play a vital role in minimizing emissions.

Exhaust Gas Recirculation (EGR) works by taking a portion of the engine's exhaust gas and directing it back into the combustion chamber. This helps to lower the combustion temperature, which reduces the formation of nitrogen oxides (NOx), a significant component of vehicle emissions. By utilizing this system, engines can achieve better fuel efficiency and lower emissions, adhering to environmental regulations.

Both PCV and EGR systems are widely used and recognized for their effectiveness in managing and controlling vehicle emissions, making their combination the correct answer to the question regarding the main types of emissions control systems.