Radiation and Radiological Disasters. A dosimeter is an instrument capable of reliably collecting, logging, processing and communicating valid real-time exposure-rate and dose-rate information. Modern real-time radiation dosimeters translate ionizing radiation, a physical entity, into an electrical signal using a variety of technologies. The electrical signal is then translated into a dose-rate by applying well-established biological models of internal radiation dose. Similarly, real-time chemical dosimeter accurately measure exposure-rate, and calculates a corresponding human dose-rate from well-established biological models of internal dose. In this context, it is interesting to read the many different definitions of "radiation dosimeter". Many of the definitions don't make the connection to radiation biology and models of internal dose. As we work to develop and transfer chemical dosimeter technologies into the marketplace, it behooves us to make the link between exposure monitoring and dosimetrics. (a) Instrument to measure dose; many so-called dosimeters actually measure exposure rather than dose. [USEPA, 1992: GL for Exposure Assessment] [USEPA, 1992a: Dermal Exposure Assessment]; (b) An instrument to measure dosage; many so called dosimeters actually measure exposure rather than dosage. "Glossary of Exposure Assessment Related Terms: A Compilation". Prepared by the Exposure Terminology Subcommittee of the IPCS Exposure Assessment Planning Workgroup for the International Programme on Chemical Safety Harmonization of Approaches to the Assessment of Risk from Exposure to Chemicals, November 1, 2001