Dragon Ball Specials - episode 2 - 07 Jun, 1988

The story begins with two young children playing with fireworks, until one of them lands in what looks like a garbage bin, starting a fire with explosions that could destroy the whole building, which a nearby Goku notices, and puts out with a hose. He warns the children never to play with fire, and have an adult around when with fireworks, and he reveals he is a volunteer fireman. Afterwards, Goku, Krillin, Master Roshi, and Yamcha (all working as volunteer firemen) put out a fire in a home, with Roshi explaining ways fires can start. (Source: Dragon Ball Wiki)