Personal radiation dose meters (dosimeters). The types seen here are: radon radiation detector (yellow, upper left); thermoluminescent dosimeter (TLD, pink, upper right), and a neutron dosimeter (green, lower right). The ring-shaped and finger glove (finger stall) dosimeters (upper centre and lower left) are variations on the TLD design. Radon is a radioactive gas naturally formed from the decay of uranium. Neutrons are particles found in atomic nuclei, which can be emitted in some types of radioactive decays. TLDs are used to detect several types of radiation, including beta radiation. These detectors are from the UK's Health Protection Agency.