As stand alone gas fired heaters they are suitable for modular installation. Each Robur heater is a separate, independent heating unit with the dual function of generating and diffusing heat. The heaters adapt to the variable heat requirements of different buildings, thus allowing the number of appliances to install to be chosen, according to different requirements. Each appliance can operate independently from the others that are installed, autonomously regulating the temperature of each single zone for the length of time desired and therefore adjusting fuel consumption to actual requirements. Robur heaters are particularly suited to locations where the modifications or expansion of the existing plant are foreseen. Finally, the Robur system guarantees constant heat even in the event of failure of one appliance, thanks to the autonomy and independence of those remaining in operation.