(a) Except as provided by Section 6001.156, an individual, other than an apprentice, must hold a license issued by the department before:
(1) installing or servicing portable fire extinguishers;
(2) installing, servicing, or certifying preengineered fixed fire extinguisher systems; or
(3) planning, supervising, servicing, or certifying the installation of fixed fire extinguisher systems other than preengineered systems.
(b) An individual who holds a license to install or service portable fire extinguishers or install and service fixed fire extinguisher systems must be an employee or agent of a registered firm.