Section 550.183 - Substantial hours requirement(a) A criminal investigator shall be eligible for availability pay only if the annual average number of hours of unscheduled duty per regular workday is 2 hours or more, as certified in accordance with § 550.184 . This average is computed by dividing the total unscheduled duty hours for the annual period (numerator) by the number of regular workdays (denominator).(b) For the purpose of this section, regular workday means each day in the criminal investigator's basic workweek during which the investigator works at least 4 hours, excluding- (1) Overtime hours compensated under 5 U.S.C. 5542 and § 550.111 ;(2) Unscheduled duty hours compensated by availability pay under 5 U.S.C. 5545a and this subpart; and(3) Hours during which an investigator is engaged in agency-approved training, is traveling under official travel orders, is on approved leave, or is on excused absence with pay (including paid holidays).(c) In computing average hours under paragraph (a) of this section, the total unscheduled duty hours in the numerator shall include-(1) Any unscheduled duty hours on a regular workday; and(2) Any unscheduled duty hours actually worked by an investigator on days that are not regular workdays.59 FR 66151, Dec. 23, 1994