Proton transfer reaction mass spectrometry (PTR-MS) is a specialist technique for detecting and identifying very small quantities amounts of organic gases in air. It is used mostly in atmospheric research, but also has applications in environmental science, pollution science, food science, and medical diagnosis. It is used as a monitoring system in various industries, e.g. measuring volatile organic compounds (VOCs) emitted by waste incineration plants. This book aims to provide a comprehensive account of the technique, and includes coverage of the basic principles, experimental techniques, and a detailed account of its various applications. Written by two leading researchers, the book will be essential reading for researchers, technicians, postgraduate students and professionals in industry.