Abstract: A gas-fired heat gun has a housing, a nozzle in the housing for directing a stream of a combustible gas in a predetermined direction along an axis in the housing, and at least two mixing tubes including an upstream tube and a downstream tube in the housing coaxial with the nozzle and downstream therefrom. Each tube has a large-diameter upstream end and a small-diameter downstream end with the downstream end of the upstream tube spacedly received within the upstream end of the downstream tube so that air is entrained axially into both upstream ends by the combustible-gas stream. A combustion chamber is provided in the housing coaxial with and immediately downstream of the downstream end of the downstream tube.