As used in this part, unless the context otherwise requires:
(1) “Commission” means the commission on firefighting personnel standards and education created by this chapter;
(2) “Firefighter” means any person in the employ of a unit of government who is a member of the fire department of such unit, is trained in firefighting or prevention of fires, and is actively engaged in such work, and whose primary livelihood is derived from such work; and
(3) “Unit of government” means any county, municipality, the state of Tennessee or any political subdivision or agency thereof, employing firefighters, all of whom must meet the minimum employment standards established by the commission.