29 C.F.R. § 785.22 : Labor — REGULATIONS RELATING TO LABOR — WAGE AND HOUR DIVISION, DEPARTMENT OF LABOR — STATEMENTS OF GENERAL POLICY OR INTERPRETATION NOT DIRECTLY RELATED TO REGULATIONS — HOURS WORKED — APPLICATION OF PRINCIPLES —SLEEPING TIME AND CERTAIN OTHER ACTIVITIES — Duty of 24 hours or more

(a) General. Where an employee is required to be on duty for 24 hours or more, the employer and the employee may agree to exclude bona fide meal periods and a bona fide regularly scheduled sleeping period of not more than 8 hours from hours worked, provided adequate sleeping facilities are furnished by the employer and the employee can usually enjoy an uninterrupted night's sleep. If sleeping period is of more than 8 hours, only 8 hours will be credited. Where no expressed or implied agreement to the contrary is present, the 8 hours of sleeping time and lunch periods constitute hours worked. ( Armour v. Wantock,323 U.S. 126(1944); Skidmore v. Swift,323 U.S. 134(1944); General Electric Co. v. Porter, 208 F. 2d 805 (C.A. 9, 1953), cert. denied, 347 U.S. 951, 975(1954); Bowers v. Remington Rand, 64 F. Supp. 620 (S.D. Ill, 1946), aff'd 159 F. 2d 114 (C.A. 7, 1946) cert. denied 330 U.S. 843(1947); Bell v. Porter, 159 F. 2d 117 (C.A. 7, 1946) cert. denied 330 U.S. 813(1947); Bridgeman v. Ford, Bacon & Davis, 161 F. 2d 962 (C.A. 8, 1947); Rokey v. Day & Zimmerman, 157 F. 2d 736 (C.A. 8, 1946); McLaughlin v. Todd & Brown, Inc., 7 W.H. Cases 1014; 15 Labor Cases para. 64,606 (N.D. Ind. 1948); Campbell v. Jones & Laughlin, 70 F. Supp. 996 (W.D. Pa. 1947).)
(b) Interruptions of sleep. If the sleeping period is interrupted by a call to duty, the interruption must be counted as hours worked. If the period is interrupted to such an extent that the employee cannot get a reasonable night's sleep, the entire period must be counted. For enforcement purposes, the Divisons have adopted the rule that if the employee cannot get at least 5 hours' sleep during the scheduled period the entire time is working time. (See Eustice v. Federal Cartridge Corp., 66 F. Supp. 55 (D. Minn. 1946).)

29 C.F.R. § 785.22