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Name: Wroblewski
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I am interested in knowing the breakdown of auto emission gases by percent.

Here is one try: auto exhaust contains carbon monoxide, unburnt hydrocarbons, water, nitrogen oxides, carbon dioxide, nitrogen, hydrogen, sulfur, and various trace metals such as lead, bromine, etc. The amount of lead has dropped drastically since the advent of unleaded gas. The proportions of the others vary with engine condition and type of driving. Water is generally about 13%. Hydrogen is 1-2%. CO is 1-5%, the rest is mostly hydrocarbons and nox, with hydrocarbons dominating during deceleration and idling and nox dominating during acceleration and cruising. Marc Fernau

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