The invention relates to a method for producing spherical activated carbon, wherein polymer globules, which comprise thermally decomposing chemical groups, are carbonized. A control section of the printer determines whether the printing jobs received by the receiving section include special printing, and causes a display section to display a list of the printing jobs including the special printing. The insulation porcelain has a groove formed on an outer peripheral wall thereof to define a portion of a reference gas passage communicating between an air inlet formed in the metallic cover and the reference gas chamber.