Section 591.230 - When does OPM establish post differential areas?(a) OPM establishes post differential areas in response to agency requests when- (1) Conditions of environment within the post differential area differ substantially from conditions of environment in the continental United States, and(2) The major Federal employers within the area believe payment of a post differential is warranted as a recruitment incentive to attract candidates from outside the post differential area to work for the Government in the post differential area.(b) If a department or agency wants OPM to consider establishing or revising the definition of a post differential area, the head of the department or agency or his or her designee must submit a request in writing to OPM.