29 C.F.R. § 541.106 : Labor — REGULATIONS RELATING TO LABOR — WAGE AND HOUR DIVISION, DEPARTMENT OF LABOR — REGULATIONS — DEFINING AND DELIMITING THE EXEMPTIONS FOR EXECUTIVE, ADMINISTRATIVE, PROFESSIONAL, COMPUTER AND OUTSIDE SALES EMPLOYEES — EXECUTIVE EMPLOYEES — Concurrent duties

(a) Concurrent performance of exempt and nonexempt work does not disqualify an employee from the executive exemption if the requirements of §541.100 are otherwise met. Whether an employee meets the requirements of §541.100 when the employee performs concurrent duties is determined on a case-by-case basis and based on the factors set forth in §541.700. Generally, exempt executives make the decision regarding when to perform nonexempt duties and remain responsible for the success or failure of business operations under their management while performing the nonexempt work. In contrast, the nonexempt employee generally is directed by a supervisor to perform the exempt work or performs the exempt work for defined time periods. An employee whose primary duty is ordinary production work or routine, recurrent or repetitive tasks cannot qualify for exemption as an executive.
(b) For example, an assistant manager in a retail establishment may perform work such as serving customers, cooking food, stocking shelves and cleaning the establishment, but performance of such nonexempt work does not preclude the exemption if the assistant manager's primary duty is management. An assistant manager can supervise employees and serve customers at the same time without losing the exemption. An exempt employee can also simultaneously direct the work of other employees and stock shelves.
(c) In contrast, a relief supervisor or working supervisor whose primary duty is performing nonexempt work on the production line in a manufacturing plant does not become exempt merely because the nonexempt production line employee occasionally has some responsibility for directing the work of other nonexempt production line employees when, for example, the exempt supervisor is unavailable. Similarly, an employee whose primary duty is to work as an electrician is not an exempt executive even if the employee also directs the work of other employees on the job site, orders parts and materials for the job, and handles requests from the prime contractor.

29 C.F.R. §541.106