It is becoming increasingly important to understand how and why semivolatile atmospheric pollutants partition between gas phase and particulate matter in the atmosphere. In this text the world's leading researchers in the field explain the significance of gas/particle ratios; physical and chemical parameters determining how semivolatiles partition in the atmosphere; how gas/particle ratio measurements are made; what artefacts occur during sampling; and novel new techniques and instruments for obtaining artefact-free results. Intended to be a reference book and a guide for those who study the gas/particle ratios of semivolatile atmospheric compounds. This book will be of interest to beginners in the field as well as those who have been involved in the field for many years and would like, in a single reference text, a comprehensive compendium of what is known about the theory and practice of gas/particle phase measurements.