c the present embodiment is also provided with burner monitoring means 29 which monitors the operating state of the rotary regenerative burner 30 and finds whether or not the operating state is normal this burner monitoring means 29 comprises temperature detecting means 29a formed such as of a thermocouple for measuring the temperature of the exhaust gas in the outlet part of the regenerator of the rotary regenerative burner 30 which will be described specifically afterward electric current detecting means 29b formed such as of an ammeter for measuring the electric current of an electric motor for driving the regenerator or the duct revolution number detecting means 29c formed such as of a rotation meter for measuring the revolution number of the regenerator or the duct part and a thermal relay 29d in a motor control circuit and operated with an overcurrent optionally this burner monitoring means 29 may comprise at least one member selected from among the temperature detecting means 29a the current detecting means 29b the revolution number detecting means 29e and the thermal relay 29d in the rotary regenerative burner with a mechanical trouble the amount of radiative heat transfer to the heating tubes 11 is decreased from the normal level by a portion due to the incomplete exchange of heat between the exhaust gas and the oxidizing agent and the outlet temperature of the fluid subjected to heating is proportionately lowered to adjust this temperature drop the heating tube 11 is provided at the outlet part thereof with.