Atmospheric Processes Laboratory is the most advanced facility in the world for the study of chemical processes in the troposphere using smog chambers. The smog chamber facility, constructed with $2.9 million in support from the Environmental Protection Agency, allows precise control of variables such as temperature, pressure, humidity, light and heat. Its unique design allows for experiments at very low reactant concentrations, a minimization of particle losses, and sampling with high flow-rate analyzers. Since its opening in 2001, a significant amount of research has been conducted on the formation of ozone and particulate matter.