A designation of radioactive sealed sources determined by the quantity and type of radioactive source, as well as any deterministic health effects. The IAEA Basic Safety Guide RS-G-1.9 establishes this categorization and it is used in the IAEA Code of Conduct.
- Category 1. As defined by the IAEA, an amount of radioactive material which, if not safely managed or securely protected, would be likely to cause permanent injury to a person who handled or were otherwise in contact with it, for more than a few minutes. It would probably be fatal to be close to this amount of unshielded material for a period of a few minutes to an hour.
- Category 2. As defined by the IAEA, an amount of radioactive material which, if not safely managed or securely protected, could cause permanent injury to a person who handled it, or were otherwise in contact with it for a short time (minutes or hours). It could possibly be fatal to be close to this amount of unshielded radioactive material for a period of hours to days.
- Category 3. As defined by the IAEA, an amount of radioactive material which, if not safely managed or securely protected, could cause permanent injury to a person who handled it, or were otherwise in contact with it for some hours. It could possibly, although it is unlikely, be fatal to be close to this amount of unshielded radioactive material for a period of days to weeks.