“Retained firefighter” and “volunteer firefighter”, A person employed by an authority–     as a firefighter, but not as a regular firefighter;      on terms under which he is, or may be, required to engage in fire fighting or, without a break in continuity of such employment, may be required to perform other duties appropriate to his role as a firefighter (whether instead of, or in addition to, engaging in fire fighting);      otherwise than in a temporary capacity; and      who is obliged to attend at such times as the officer in charge considers necessary, and in accordance with the orders that he receives.    ,