Vehicle emissions are the gasses released through a vehicle's exhaust system. Carbon monoxide, hydro-carbons and sulfur-oxide along with nitrogen-oxides and particulates are all harmful vehicle emissions that spew out of the exhaust gasses of an internal combustion engine. While catalytic converters were designed to reduce these harmful vehicle emissions, automobile designers worldwide to explore new methods of vehicle propulsion, such as electricity and hydrogen, that produce little or no pollution.
The automobile industry has been working on improving vehicle emissions since the 1950s. This started with the first positive crankcase ventilation system valve, or PCV valve, being introduced on American-made vehicles. This device was designed to draw harmful vehicle emissions out of the exhaust system and run it through the combustion system to burn off the toxins.
In the United States in 1961, California was the first state to mandate the PCV system on all new vehicles sold. This was done in an attempt to slow the growth of smog and pollution. New York state was the next to mandate this system, and by 1964 all vehicles sold in the United States were required to have a PCV system installed. The requirement was soon implemented worldwide.
The introduction of clean air laws and restrictions of harmful vehicle emissions around the world soon paved the pathway for unleaded gasoline to be used extensively in vehicles. The lead found in regular gasoline was causing the platinum in catalytic converters to become plugged and damaged. General Motors Corporation led the way for car manufacturers and asked that only unleaded fuels be used in new vehicles — this had now been a new vehicle release requirement since 1975.
Prior to the introduction of unleaded fuel, vehicle manufacturers were simply de-tuning vehicles in order to meet strict exhaust emission requirements. This caused vehicles to operate with very poor fuel mileage. By burning unleaded fuels, vehicles could once again be tuned for optimum performance and utilize a catalytic converter to reduce vehicle emissions effectively.
Many new engine and exhaust systems have been designed to combat the harmful pollutants that are released into the atmosphere from the tailpipes of vehicles. Smog systems, or air injection and exhaust gas recirculation systems, have helped to clean vehicle emissions a great deal as compared to the 1950-era vehicles. Hybrid gas and electric automobiles and new technology such as hydrogen-powered cars that produce water as exhaust have hit the market.