(a) An agency may require that an employee with an uncommon tour of duty accrue and use leave on the basis of that uncommon tour of duty. The leave accrual rates for such employees shall be directly proportional (based on the number of hours in the biweekly tour of duty and the accrual rate of the corresponding leave category) to the standard leave accrual rates for employees who accrue and use leave on the basis of an 80-hour biweekly tour of duty. One hour (or appropriate fraction thereof) of leave shall be charged for each hour (or appropriate fraction thereof) of absence from the uncommon tour of duty.

(b) When an employee is converted to a different tour of duty for leave purposes, his or her leave balances shall be converted to the proper number of hours based on the proportion of hours in the new tour of duty compared to the former tour of duty.

(c) An agency shall establish an uncommon tour of duty for each firefighter compensated under part 550, subpart M, of this chapter. The uncommon tour of duty shall correspond directly to the firefighter's regular tour of duty, as defined in § 550.1302 of this chapter, so that each firefighter accrues and uses leave on the basis of that tour.

(d) In applying § 550.805(g) of this chapter, and §§ 630.306(b), and 630.310(d), the referenced number of hours for full-time employees (416 hours and 208 hours) shall be proportionally adjusted based on the percentage amount by which the number of hours in the uncommon tour of duty exceeds the number of hours in a regular full-time tour of duty. For example, if the uncommon tour of duty consists of 120 hours in a biweekly pay period instead of the 80 hours for a regular full-time employee, the percentage adjustment would be 50 percent [(120/80) − 1]; accordingly, 416 hours would be converted to 624 hours and 208 hours would be converted to 312 hours.