Film badges are widely used for personnel monitoring because:

Film badges are widely used for personnel monitoring primarily because they provide a permanent record of radiation exposure. These badges contain photographic film that darkens in proportion to the amount of radiation exposure over time. This allows for accurate and long-term tracking of an individual's exposure history. The recorded information can be analyzed later to assess cumulative exposure, which is critical for ensuring compliance with regulatory limits and for the health and safety of personnel working with radiation.

While immediate indication of exposure is an important aspect of some dosimeter types, film badges do not offer a real-time readout. Instead, after a specified wear period, the badges are sent to a processing facility to be developed and analyzed. This processing does not provide immediate feedback but ensures a reliable historical record.

Regarding beta and X-radiation, film badges are affected by these types of radiation, although they are primarily designed to measure gamma radiation. Certain designs may include filters to help differentiate between different types of radiation, but they are not completely unaffected by them. Thus, while film badges have many advantages, including the potential to evaluate exposure from different sources, the statement regarding their permanence is what makes them particularly valuable.