Keeping the air clean is one of the most important aims in environmental protection. The fugitive emissions especially volatile organic compounds (VOC's) and the ozone-precursors nitrogen oxides (NOX) have a great impact on the quality of the atmospheric air. Fugitive emissions from leaking valves, pumps and flanges are one of the main problems in industrial applications. Elimination or reduction of fugitive emissions could potentially save the industry millions of dollars and prolong scarce resources. This book discusses fugitive emissions, their sources and their impact on the environment.