An aspect of the present invention provides an internal and the like. The internal is easily handled and is capable of yielding a satisfactory defoaming effect. An internal (50) is used in a fluidized bed reaction device (1), in which a first material and a second material are brought into contact with each other and reacted with each other. The internal (50) is attached to a ceiling part of the fluidized bed reaction device (1), and includes a plurality of chains (21).