This week we welcome one of the top IAQ researchers in the world William "Bill" Nazaroff, PhD. Dr. Nazaroff is a Daniel Tellep Distinguished Professor at the University of California Berkeley and has served as a Faculty Senior Scientist at Lawrence Berkeley Laboratory. His research centers on air quality engineering, emphasizing two themes: pollutant dynamics in indoor air and exposure science. On the first, his primary interest is to better understand the physics and chemistry that control the concentrations, fates, and effects of pollutants in indoor environments. On the second topic, he and his group apply basic knowledge about air pollutants to build a quantitative and mechanistic understanding of the relationship between emissions from sources and consequent human exposures. His group pursues research through a combination of laboratory and field experiments, modeling, and data analysis. In recent years, in addition to maintaining vigorous activities in the two primary areas, he has had a growing concern about and interest in the themes of sustainability, climate change, and energy-use efficiency. He has recently been pursuing research opportunities in these newer thematic areas, especially when opportunities arise that intersect with his primary research themes.