The subject of the invention is a hot gas generator (8), particularly for a dehydration or drying unit, the generator comprising a burner or hearth (9) and being characterized in that it comprises at least one exchange circuit (10) comprising at least one pipe through which the gas to be heated flows, the pipe comprising a cool gas inlet end (11) and a hot gas discharge outlet (12), the pipe having a surface for heat exchange between the combustion gases generated by the burner or hearth (9) and the gas to be heated which flows through the pipe, the pipe also providing a physical barrier between the heated gases and the combustion gases generated by the burner or hearth. Application to producing a drying or dehydration installation.