Automobile emissions are gasses expelled from a vehicle's exhaust system. These automobile emissions contain many types of toxic gasses, many of which can harm the environment as well as cause illness to humans if they are exposed to the emissions for an extended period of time. Catalytic converters and oxygen pumps and sensors installed on the vehicle do their part in keeping automobile emissions to a minimum. Hydrocarbons, carbon monoxide, sulfur oxide and particulate matter such as soot are some of the most prevalent automobile emissions.
Exhaust gasses are not the only type of automobile emissions that can cause problems with the environment. Evaporative gasses, such as motor oil fumes, grease burning that evaporates off of a hot running engine, and fumes that come from adding fuel to a vehicle, are also dangerous automobile emissions that must be monitored and controlled. Methane is also a factor in automobile emissions; however, it is nontoxic in nature, and there is debate over the amount of concern that should be attributed to the gas. Most automobile emissions are greenhouse gas-qualified. Put in the most basic terms, this means that the emissions are dangerous or detrimental to the environment.
The Positive Crankcase Ventilation (PCV) valve was the first effort of automobile manufacturers designed to address the automobile emissions problem head-on. The PCV valve allows the gasses from the engine's crankcase to be recycled into the intake system. From there, they are introduced into the combustion chamber to be re-ignited. This causes less dangerous emissions to be spewed out of the exhaust and into the atmosphere. The PCV valve was first implemented in the US state of California in 1961 and became standard fare on most vehicles sold in the US by 1964—the PCV valve soon become standard on all vehicles worldwide.
Automobile emission testing first began in California with the 1966 model year. This was the first attempt anywhere to actually test the tailpipe emissions on a regular basis. By the release of the 1968 vehicle model year, this practice was nationwide in the US. The fuel shortage as well as the ecology push found 1974-released vehicles actually being de-tuned and equipped to reduce engine emissions as well as improve fuel mileage. The catalytic converter made its debut in 1975, and with it came the move to unleaded fuel only—this marked the beginning of an attempt to seriously address the emission problems of new vehicles.