Section 550.903 - Establishment of hazard pay differentials(a) A schedule of hazard pay differentials, the hazardous duties or duties involving physical hardship for which they are payable, and the period during which they are payable is set out as appendix A to this subpart and incorporated in and made a part of this section.(b) Amendments to appendix A of this subpart may be made by OPM on its own motion or at the request of the head of an agency (or authorized designee). The head of an agency (or authorized designee) may recommend the rate of hazard pay differential to be established and must submit, with its request for an amendment, information about the hazardous duty or duty involving physical hardship showing-(1) The nature of the duty;(2) The degree to which the employee is exposed to hazard or physical hardship;(3) The length of time during which the duty will continue to exist;(4) The degree to which control may be exercised over the physical hardship or hazard; and(5) The estimated annual cost to the agency if the request is approved.56 FR 20344, May 3, 1991, as amended at 64 FR 69179, Dec. 10, 1999