Maryland Code, Business Occupations and Professions § 12-301

(c) This section does not apply to an employee of a gas company regulated by the Public Service Commission while making a connection to a gas appliance for domestic purposes or while installing, repairing, maintaining, replacing, or performing any other work on a natural gas, propane gas, or other gas distribution system, including customer-owned gas piping systems.

(d) This section does not apply to an individual performing work that is only incidental to the licensee providing or assisting in providing plumbing services.

(e) This section does not apply to an individual who, without compensation, provides plumbing services that the Board defines by regulation to be only incidental plumbing services.

(f) This section does not apply to an employee of a building owner, manager, or maintenance company who provides plumbing services that the Board defines by regulation to be only minor plumbing repair services.

(g) This section does not apply to an individual who is licensed as an appliance installer in Allegany County, Frederick County, Garrett County, or Washington County while acting within the scope of the license.

(h) This section does not apply to an individual who is licensed in Washington County to work as or for a septic system installer or an on-site utility contractor installing water or sewer service in the county at least 5 feet from a building being served.

(i) Subsection (a)(3) and (4) of this section does not apply to an individual licensed by the State Board of Heating, Ventilation, Air-Conditioning, and Refrigeration Contractors while servicing an existing propane gas or existing natural gas appliance if the individual has completed a manufacturer's training course certifying competence to work on that particular type of appliance.