This grant funds a research project by Rachel Adams, research scientist at the University of California, Berkeley, to expand our understanding of how microorganisms shape the chemistry of indoor environments. Adams and colleagues will undertake a series of controlled chamber experiments to identify the boundaries of microbial production of chemical volatile organic compounds due to humidity on various surfaces fundamental to homes, including drywall, carpets, and wood. The team also plans to investigate the relative importance of growth substrate, including the dust matrix in which most household environmental microbes are embedded, and, by varying substrate and inoculum in a controlled manner, of microbial taxonomic identity. In addition to creating a more thorough inventory of MVOCs, these research activities will determine how changing environmental conditions underlie the microbial processes that determine chemical emissions. This project will result in new knowledge about microbially mediated processes that impact the chemistry of indoor spaces. The results will be shared through peer-reviewed publications and presentations at meetings and workshops. Two undergraduate, one master’s and one Ph.D. student will be trained.