Abstract: A gas-fired heater, in particular of the type having radiant bodies (6) to be heated by gas flames, in which fuel gas and combustion air are supplied under pressure to at least one burner nozzle (19, 10) in a proportion ensuring complete combustion, and further comprising an air chamber (9) in association with the or each burner (20), and the chamber having an outlet terminating in the ambient space of sufficient dimensions to offer no essential resistance to air flowing out into the ambient. A venturi (10) extends from the chamber (9) into the burner (20). A gas supply nozzle (18) is arranged coaxially in front of the throat of the venturi (19) within the chamber (9). Means (3, 7, 8) are provided for supplying air to the chamber (9) in a quantity slightly in excess of that needed for complete combustion at maximum capacity of the burner (20).