D.C. Mun. Regs. tit. 17, r. 17-402
The Board of Examiners (appointed by the Mayor in accordance with the provisions of D.C. Code § 2-2402 (1981)) shall meet not less than thirty (30) times per year for the examination of applicants for steam and other operating engineer licenses and for the transaction of other business which may be necessary in connection with their office.
The examination for steam and other operating engineer licenses shall include questions, diagrams, and practical tests of sufficient scope to thoroughly demonstrate to the Board that the applicant has the necessary experience; knowledge of the basic principles involved in the safe operation, care, and maintenance of the applicable equipment; and is qualified to take complete charge of and safely operate the engine or steam or hot water boiler or machinery of the class for which an application for a license has been made.
An applicant for a license for portable and construction equipment operator shall not be required to be examined unless the Board is in doubt about the applicant's ability as expressed by his or her statement of experience and endorsers.
D.C. Mun. Regs. tit. 17, r. 17-402