Maryland Business Occupations and Professions Section 12-401

      (a)      A person may engage in the business of providing plumbing services if:

            (1)      the person is a master plumber or holder of a limited master plumber license; or

            (2)      the person:

                  (i)      designates a master plumber or holder of a limited master plumber license who actively directs, controls, and is responsible for all plumbing services; and

                  (ii)      otherwise provides the plumbing services in accordance with this title.

      (b)      A person may engage in the business of providing propane gas services if:

            (1)      the person is the holder of a propane gas fitter certificate; or

            (2)      the person:

                  (i)      designates a holder of a propane gas fitter certificate who actively directs, controls, and is responsible for all propane gas services; and

                  (ii)      otherwise provides the propane gas services in accordance with this title.

      (c)      A person may engage in the business of providing natural gas services if:

            (1)      the person is the holder of a master natural gas fitters license; or

            (2)      the person:

                  (i)      designates a holder of a master natural gas fitters license who actively directs, controls, and is responsible for all natural gas services; and

                  (ii)      otherwise provides natural gas services in accordance with this title.