Film badges are used to monitor personal exposure to beta and gamma radiation. To assess various radiations simultaneously, a strip of film is covered with absorbers. By varying the type and thickness of the absorbers, one can determine skin dose, dose to the lens of the eye, and whole-body dose. Some film badges have a small window shielded by a sheet of mylar which can detect beta radiation, and one or more sections shielded by metal foils for detecting gamma radiation. The radiation exposure of the film is determined by the degree of darkening of the film after the film is developed.
Film badges look like badges and can be clipped onto a pocket or a belt.
While film badges and TLDs measure a workers dose over an extended period of time, pocket dosimeters measure a worker's radiation dose each day. Rather than waiting weeks, pocket dosimeters can detect whether a worker might have received a dangerous dose during a given workshift. In principle, one should wear a film badge or TLD and a pocket dosimeter at the same time. They are basically devices that can store an electric charge. They consist of an exterior wall, which is essentially a plastic tube coated with a conducting material, and an interior central wire which is insulated from the outer wall.