This grant funds an extended field experiment, Chemical Assessment of Surfaces and Air (CASA), that will bring together a dozen research groups from across the country to advance the state of understanding of indoor chemistry. Led by Delphine Farmer of Colorado State University and Marina Vance of UC Boulder, CASA will occur at the Net-Zero Energy Residential Test Facility, a test house laboratory managed by the National Institute of Standards in Gaithersburg, Maryland. CASA will consist of a diverse series of experiments that revolve around disturbing a well-controlled, heavily-sensored, indoor environment in a variety of ways and observing how those disturbances affect the evolution of the chemical processes going on inside. Questions for investigation involve how perturbations in indoor environmental conditions, such as temperature, relative humidity, and ventilation rate, affect indoor surface and air composition; how the introduction of novel molecules like ozone or volatile organic compounds influence the chemical transformations happening in the air and on surfaces; and how changes to the acidity, reactivity, or other properties of indoor surfaces like countertops and floors affect indoor chemical processes. Grant funds will support the organization of CASA, coordination of the research teams, and associated data infrastructure and community-building activities aimed both at participating research groups and at connecting findings with the growing body of indoor chemistry research. The project will result in at least 10 new peer-reviewed publications and 20 conference presentations, a more developed website with links to an accessible data archive, data analysis tutorials, a set of unified datasets, and a conference for study participants to discuss preliminary findings.