Some employees are covered because their work, although not actually
a part of such production, is ``closely related'' and ``directly
essential'' to it. This group of employees includes bookkeepers,
stenographers, clerks, accountants and auditors and other office and
white collar workers, and employees doing payroll, timekeeping and time
study work for the producer of goods; employees in the personnel,
labor relations, advertising, promotion, and public relations activities
of the producing enterprise; work instructors for the producer;
employees maintaining, servicing, repairing or improving the buildings,
machinery, equipment, vehicles or other facilities used in the
production of goods for commerce, 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 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 illustrative, rather than
exhaustive, of the group of employees of a producer who are ``engaged in
the production of goods for commerce'' by reason of performing
activities closely related and directly essential to such production.