This part does not apply to:
(1) The filling or charging of a portable fire extinguisher by the manufacturer prior to its initial sale;
(2) The servicing by a firm of its own portable fire extinguishers or fixed systems, or both, by its own personnel specially trained for such servicing;
(3) The sale, installation, maintenance or service of a fire protection sprinkler system by a fire protection sprinkler contractor registered pursuant to part 1 of this chapter;
(4) Firms engaged in the retailing or wholesaling of portable fire extinguishers as defined in § 62-32-203, but not engaged in the installation or recharging of them; or
(5) Fire departments recharging portable fire extinguishers as a public service where no charge is made; provided, that members of the fire department performing such a public service shall be trained in the proper filling and recharging of the fire extinguishers.