OSU maintains a wide variety of research activities, including a nuclear reactor. Thus, radioisotopes present can vary widely in both identities and quantities. However, if one excludes the reactor itself and the large sealed isotope sources at the Radiation Center, then OSU has only a dozen or so different radioisotopes of any importance, with quantities in any container ranging from sub-microcuries to a few tens of millicuries with only rare instances of larger quantities of tritium. The bulk of the person-hours at OSU around radioisotopes involve unsealed chemicals containing tritium, carbon-14, phosphorous-32, sulfur-35, and iodine-125 for use as tracers in various life sciences research. Although use of the reactor involves the largest quantity of radioisotopes, this life sciences research constitutes the majority of the personnel risk.