Hydrocarbon as pollutants

In addition to nitrogen oxides and carbon monoxide, an automobile engine also emits unburned hydrocarbons as pollutants. These organic compounds, which are composed entirely of carbon and hydrogen, are the principal components of gasoline (Section 25.1). A typical engine without effective emission controls emits about 10 to 15 g of these compounds per mile. Current standards require that hydrocarbon emissions be less than 0.25 g/mi. 

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