A dual illumination system is disclosed for use with an imaging apparatus. The piezoelectric film has a crystal structure of pseudo-cubic crystal, tetragonal crystal, orthorhombic crystal, monoclinic crystal or rhombohedral crystal, or has a state that at least two of the crystal structures coexist. The substrate being made of a material exhibiting a very high gas flux for the gas that the membrane is to let through. The method comprises the following: indicate identification information on a tag regarding the piping structure; and attach the tag to the piping structure.