The RIOPA project comprised three studies, one funded by the Mickey Leland National Urban Air Toxics Research Center (NUATRC) and two funded by HEI, that investigated seasonal concentrations of 16 VOCs, 10 carbonyls, and PM2.5 in homes in Los Angeles CA, Houston TX, and Elizabeth NJ. The project was jointly funded and reviewed by a Special Review Panel of the two organizations. It generated a rich database on concentrations of air toxics and PM2.5 in the personal breathing zone of 100 adults in each city as well as inside and outside their homes. Part I describes the sample collection methods and analyses for the VOCs and carbonyls. Information on PM2.5 composition is provided in Part II.