5 CFR §550.181

1. (a)Each employee meeting the definition of criminal investigator in § 550.103, and fulfilling the conditions and requirements of 5 U.S.C. 5545a and §§ 550.181 through 550.186, must receive availability pay to compensate the criminal investigator for unscheduled duty in excess of the 40-hour workweek based on the needs of the employing agency, except as provided in paragraph (b) of this section.
2. (b)Any Office of Inspector General that employs fewer than five criminal investigators may elect not to cover such criminal investigators under the availability pay provisions of 5 U.S.C. 5545a.