Cultural property inside museums - textiles and works of art on paper and pigments and leather bindings, for example - can be threatened by outdoor pollutants, such as automobile exhaust fumes, and by pollutants generated from indoor sources, such as gases from cleaning products. Indoor-generated pollutants generally pose the greatest threat to artefacts because of their continuous and close proximity. The focus of this volume, based on the Getty Trust Museum Monitoring Project as well case studies, is environmental monitoring for common gaseous pollutants, with emphasis on passive sampling. The volume begins with an overview of the history and nature of pollutants of concern to museums and a discussion of the challenges facing scientists, conservators, and collections managers seeking to develop target pollutant guidelines to protect cultural property. Subsequent chapters address passive sampling, the planning and conducting of an air quality monitoring program, and the interpretation of results and mitigation considerations. The appendix is a comprehensive compilation of the major gaseous pollutants encountered in museums, their sources, and the at-risk materials.