"The PAG Manual [EPA 1992] establishes protective actions based on the ability to control exposure to the radioactive material and the exposure pathways that are expected to exist as a nuclear incident progresses. This approach results in classifying the response to a nuclear incident into three phases, i.e., early, intermediate, and late (recovery) phase. (1) The early phase of a nuclear incident is from the beginning of the incident until the release of radioactive material is under control and is characterized by the need to make immediate decisions for protective actions. (2) The intermediate phase is the period beginning after the release of radioactive material has been brought under control or has stopped and is characterized by the ability to obtain reliable radiological measurements as a basis for decision making. (3) The late (recovery) phase is the period in which recovery actions are conducted to bring radiation levels to levels acceptable for the area to be returned to unrestricted use". (Health Physics Society, Background Information on "Guidance for Protective Actions Following a Radiological Terrorist Event" Position Statement of the Health Physics Society, 2004, p. 4)