29 CFR § 780.11 - Exempt and nonexempt work during the same workweek.

Where an employee in the same workweek performs work which is exempt under one section of the Act and also engages in work to which the Act applies but is not exempt under some other section of the Act, he is not exempt that week, and the wage and hour requirements of the Act are applicable (see Mitchell v. Hunt, 263 F. 2d 913; Mitchell v. Maxfield, 12 WH Cases 792 (S.D. Ohio), 29 Labor Cases 69, 781; Jordan v. Stark Bros. Nurseries, 45 F. Supp. 769; McComb v. Puerto Rico Tobacco Marketing Co-op Ass'n, 80 F. Supp. 953, affirmed 181 F. 2d 697; Walling v. Peacock Corp., 58 F. Supp. 880–883). On the other hand, an employee who performs exempt activities during a workweek will not lose the exemption by virtue of the fact that he performs other activities outside the scope of the exemption if the other activities are not covered by the Act.