What happens when gasoline is burned in a car?

Dear Tom,
Cars are often mentioned as being major polluters of the air. What happens when gasoline is burned in a car?
Joyce Minorston, Chicago
Dear Joyce,
The complete combustion of one pound of gasoline combines with gases in the atmosphere to produce 3.1 pounds of carbon dioxide and 1.4 pounds of water vapor as exhaust gases. If combustion is not complete, and as a rule it isn’t, then carbon monoxide is also one of the gaseous byproducts. Carbon dioxide exists naturally as a trace component of the atmosphere, currently amounting to 415 parts per million of dry air. Despite its low concentration, it is a powerful “greenhouse gas” in that it contributes to the atmosphere’s ability to retain heat (the so-called greenhouse effect). Carbon monoxide is a colorless, tasteless, odorless gas that exists naturally only in minute quantities in the free atmosphere.

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