Where an employee in the same workweek performs work which is exempt
from the overtime requirements of the Act under section 13(b)(9), and
also engages in work to which the overtime requirements apply, he is not
exempt from overtime provisions of the Act in that week. (See McComb v.
Puerto Rico Tobacco Marketing Co-op Ass'n., 80 F. Supp. 953, affirmed,
181 F. 2d 697; Mitchell v. Hunt, 263 F. 2d 913; Abram v. San Joaquin
Cotton Oil Co., 46 F. Supp. 969; McComb v. del Valle, 80 F. Supp. 945;
Walling v. Peacock Corp., 58 F. Supp.
880.) As explained in Sec. 793.13, work which does not come within the
occupational duties of an announcer, news editor, or chief engineer, or
which is not related and incidental thereto, is not exempt work under
section 13(b)(9). The mere isolated or occasional performance of
insubstantial amounts of such nonexempt work will not defeat the
exemption for the employee. Where, however, an employee, in a particular
workweek, performs a substantial amount of nonexempt work to which the
overtime provisions of the Act are applicable, the employee is not
exempt under section 13(b)(9) in that workweek. For administrative
purposes an employee who spends 20 percent or more of the hours he works
in a workweek in such nonexempt work, will not be considered exempt
under section 13(b)(9) in that workweek.