Differing legislation between the countries or unions of countries involved in pollution reduction has turned gas measuring technology into such an extremely extensive and complex field that only a few specialists in environmental agencies and the automobile industry have a grasp of it. This book is intended as an overview of the basics of exhaust gas measuring technology describing the interrelation between emissions, immissions and the effects of pollutants. It aims to provide experts and students alike with an understanding of the interrelationships and details within this field. The results presented are based on the experience gathered by the author during work spanning more than two decades in the automobile industry.