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Personal Radiation Monitor

A personal radiation monitor is often referred to as a “badge” or a “film badge.” Some types of these monitors still use film while others use a small, thin crystal (often called a "TLD") or a special powder. All of these devices are used to measure the amount of radiation to which someone has been exposed, usually in an occupational setting (e.g., an x-ray technologist in a hospital).

Each type of personal radiation monitor works differently:

  • The degree of darkening on a film badge is related to the amount of radiation exposure.
  • The amount of light given off when the thin crystal is heated is related to the amount of radiation exposure.
  • The amount of light given off when the special powder is excited by a laser of a certain wavelength is related to the amount of radiation exposure.

These monitors generally are issued to people exposed to penetrating radiation such as x rays and medium- to high-energy gamma rays. They are not routinely issued to people working with radionuclides in academic research laboratories for two reasons: the activity of the radioactive materials used is too small to measure external exposure and the most commonly used radionuclides are not external radiation exposure hazards (many are medium- and low-energy beta emitters).