29 CFR §776.18

1. (a)Covered employments illustrated. Some illustrative examples of the employees employed by a producer of goods for interstate or foreign commerce who are or are not engaged in the “production” of such goods within the meaning of the Act have already been given. Among the other employees of such a producer, doing work in connection with his production of goods for commerce, who are covered because their work, if not actually a part of such production, is “closely related” and “directly essential” to it, 86 are such employees as bookkeepers, stenographers, clerks, accountants and auditors, employees doing payroll, timekeeping and time study work, draftsmen, inspectors, testers and research workers, industrial safety men, employees in the personnel, labor relations, advertising, promotion, and public relations activities of the producing enterprise, work instructors, and other office and white collar workers; employees maintaining, servicing, repairing or improving the buildings, 87 machinery, equipment, vehicles, or other facilities used in the production of goods for commerce, 88 and such custodial and protective employees as watchmen, guards, firemen, patrolmen, caretakers, stockroom workers, and warehousemen; and transportation workers bringing supplies, materials, or equipment to the producer's premises, removing slag or other waste materials therefrom, or transporting materials or other goods, or performing such other transportation activities, as the needs of production may require. These examples are intended as illustrative, rather than exhaustive of the group of employees of a producer who are “engaged in the production” of goods for commerce, within the meaning of the Act, and who are therefore entitled to its wage and hours benefits unless specifically exempted by some provision of the Act.
2. (b)Employments not directly essential to production distinguished. Employees of a producer of goods for commerce are not covered as engaged in such production if they are employed solely in connection with essentially local activities which are undertaken by the employer independently of his productive operations or at most as a dispensable, collateral incident to them and not with a view to any direct function which the activities serve in production. It is clear, for example, that an employee would not be covered merely because he works as a domestic servant in the home of an employer whose factory produces goods for commerce, even though he is carried on the factory payroll. To illustrate further, a producer may engage in essentially local activities as a landlord, restauranteur, or merchant in order to utilize the opportunity for separate and additional profit from such ventures or to provide a convenient means of meeting personal needs of his employees. Employees exclusively employed in such activities of the producer are not engaged in work “closely related” and “directly essential” to his production of goods for commerce merely because they provide residential, eating, or other living facilities for his employees who are engaged in the production of such goods. 89 Such employees are to be distinguished from employees like cooks, cookees, and bull cooks in isolated lumber camps or mining camps, where the operation of a cookhouse may in fact be “closely related” and “directly essential” or, indeed, indispensable to the production of goods for commerce. 90