- There are four types of vehicle pollutants that emissions standards try to control and reduce: Hydrocarbons (HC) that result from unburned fuel or fuel evaporation released into the atmosphere and which may cause eye, throat and lung irritation; carbon monoxide (CO) produced by partially burned fuel that is colorless, odorless and lethal if inhaled in large quantities; oxides of nitrogen (NOx) generated by the intense heat during combustion that produce ozone in smog and may irritate lungs and eyes; and particulates, or solid particles of carbon soot produced by a rich air-fuel mixture in the engine, which may easily find their way into your respiratory system.
- During the establishment of the Environmental Protection Agency (EPA) in the United States in 1970, scientists discovered that from 1900 to 1970, the rise in vehicle use around the world dangerously increased the presence of nitrogen oxide in the atmosphere by 690 percent. The EPA then received the task of controlling and reducing air pollutants, including those from automobiles through the implementation of federal auto emissions standards.
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Smog covers a French town at midday-photo courtesy of Lamiot at Commons Wikimedia.org.Chemicals released from vehicles' exhaust systems become airborne and combine with oxygen, nitrogen and other elements in the atmosphere. In the worst cases, these harmful chemicals can be seen as smog during sunlight, specially in large industrialized cities. Air pollution lets dangerous radiation from the sun enter the atmosphere and prevents heat from being released into space. This global warming effect, according to scientists, will have a negative impact on world food supplies, sea level, weather and human health if it gets out of control. - Auto emissions standards have identified three main sources of air pollution coming from internal combustion engines: 20 percent of harmful emissions come from crankcase vapors, 20 percent from fuel vapors and 60 percent from engine exhaust.
- To reduce those harmful emissions and comply with emissions standards, auto manufacturers have integrated specific--and some times sophisticated--systems into their engines. These include positive crankcase ventilation, evaporative emissions control, exhaust gas recirculation, air injection, thermostatic air cleaner, catalytic converter and computer control systems.
