Contaminants in indoor air have enormous impact on human health, productivity, building energy use, and sustainability. This course focuses on important contaminants, fundamental tools, and methodologies to measure and model the indoor environment, and on engineering solutions to improve indoor air quality. The course covers a rationale and motivation for the investigation of indoor contaminants, important contaminants and sources, the use of mass balances to assess indoor concentrations, fundamental transport and transformation processes that occur indoors, indoor exposure assessment, and methodologies to assess costs and benefits for technologies and techniques to improve indoor air. The course explicitly links the air inside of buildings to building materials, energy use, outdoor air quality, and human health.