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Globe & seagull
Date Issued: 1970-10-28
Postage Value: 6 cents

Commemorative issue
Anti-pollution
Globe & seagull

The techniques used for the removal of air pollutants from stationary sources are distinguished between those that remove solids and those that remove gases. Extremely small particulates (solids) are the most dangerous because they may penetrate deeply into human lungs. Emission of gases generally is more difficult to control than solids. Automobile emissions have been reduced by lowering engine combustion temperatures and by completing the oxidation of unburned gases by means of a catalytic converter in the exhaust system.

Topic: Bird (278)  

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