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Speaker 1: Welcome to Brainstuff from hose stuff works dot com where

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Speaker 1: smart happens. Hi. I'm Marshall Brain with today's question, why

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Speaker 1: doesn't gasoline burn cleanly? Why do we end up with

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Speaker 1: things like smog and ozone that pollute disguise? Gasoline is

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Speaker 1: a liquid formed almost purely of carbon and hydrogen. If

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Speaker 1: you could somehow burn gasoline as a vapor with a

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Speaker 1: hot flame and plenty of oxygen, you would get nearly

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Speaker 1: pure carbon dioxide and water as the combustion products. That's

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Speaker 1: why you can burn natural gas, LP gas and kerosene

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Speaker 1: indoors in the winter, and appropriately designed kerosene heater, for example,

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Speaker 1: can be ventless. Automobile exhaust, unfortunately, contains a lot more

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Speaker 1: than carbon dioxide and water. The most important pollutants and

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Speaker 1: car exhaust include first, carbon monoxide, which is a poison.

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Speaker 1: Carbon monoxide is formed because combustion is incomplete in the cylinder,

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Speaker 1: not enough oxygen is available fast enough to react completely

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Speaker 1: with all the carbon available. Second is nitrogen oxides. Because

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Speaker 1: of the pressure and temperature inside the cylinder, nitrogen and

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Speaker 1: oxygen in the air combined in various ways, we would

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Speaker 1: rather it didn't. And third is unburned hydrocarbons. Not all

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Speaker 1: of the hydrocarbons participate in the reaction because there's so

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Speaker 1: little time available during the combustion phase. There can also

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Speaker 1: be some impurities, like sulfur in the gas to form

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Speaker 1: sulfur oxides. The idea behind a kettalytic converter is to

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Speaker 1: try to eliminate the carbon monoxide, nitrogen oxides, and hydrocarbons

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Speaker 1: by reacting them with plenty of oxygen on a platinum catalyst. However,

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Speaker 1: catalytic converters aren't perfect either, so some of the pollutants

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Speaker 1: still escape. On hot summer days, we see the effect

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Speaker 1: of these pollutants in the form of smog and ozone.

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Speaker 1: Nitrogen oxides and hydrocarbons mixed with air and get bombarded

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Speaker 1: by ultraviolet rays and sunlight. Nitrogen dioxide releases an oxygen atom,

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Speaker 1: which combines with oxygen gas to form O three or

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Speaker 1: ozone at ground level. Do you have any ideas or

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Speaker 1: suggestions for this podcast? If so, please send me an

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Speaker 1: email at podcast at how stuff works dot com. For

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Speaker 1: more on this and thousands of other topics, go to

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Speaker 1: how stuff works dot com and be sure to check

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Speaker 1: out the brain Stuff blog on the how stuff works

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Speaker 1: dot com home page. This episode of brain Stuff is

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