Film or thermoluminescent dosimeter badges give radiographers a way of determining the total radiation exposure for a period of time. Radiation exposed film turns black when it is developed. Plastic, aluminum, cadmium and/or lead filters in the holder for the film packet allow determination of types of radiation and its approximate energy. Lead filters out low energy radiation so that the film records only high energy radiation exposure under the lead filters. Plastic filters out most beta particles. Aluminum and cadmium filter out different energies of X-rays as well as beta particles. Cadmium converts neutrons into gamma radiation so that the neutron exposure may be measured. Unfortunately, film also detects heat and mechanical damage so the film dosimeters must be handled carefully.
National Dosimetry Services (NDS) offers dosimetry monitor services in Canada. This service is offered by Health Canada.
How Does Thermoluminescent Dosimetry Work gives an excellent description on the function of TLD.
Comparison of Dose Response in Fricke Dosimeters and Thermoluminescent Detectors describes how these devices work. Under construction!!!