"Introduction Many of us will recall the winter smog of the 1950s in Europe??a combination of smoke and fog??and the need to put a scarf or handkerchief over one's mouth when venturing outside. In those days@ we were remarkably tolerant of smog@ almost accepting that it was a fact of life in winter. We heated our homes with coal fires@ and factories belched out smoke as we traveled to the city by steam train. Occasionally@ we had the luxury of riding in a motor car. This was considered very much a symbol of quality of life. The main concern seemed to be the grimy buildings@ which needed to be cleaned every so often. We knew that human health was affected@ but our priorities were different. Indeed@ if we had to list the sources of this smog pollution in those early days@ we probably would have excluded motor vehicles and no one would have even understood the term ""fuel reformulation."" Time has moved on. Nowadays@ concern is expressed about how to arrest global warming and minimize the impact of air pollution on the living environment@ and how we can improve air quality. We realize that the air that we breathe is not precisely 20% oxygen and 80% nitrogen@ but very much a cocktail of chemical compounds@ of which oxygen and nitrogen are major components. Other compounds that we breathe each day include carbon monoxide@ hydrocarbons (the most notorious of which is benzene)@ nitric oxide and nitrogen dioxide (both referred to as nitrogen oxides)@ small particles or particulates??some of which are formed by chemical reaction in the atmosphere@ sulfur dioxide@ and ozone. Let us examine each pollutant in turn and make a first assessment of their relative importance and influence on our health."
SAE R-232-2001 history
2001SAE R-232-2001 Improving Air Quality Progress and Challenges for the Auto Industry