At least one kind of solvent selected from among nitromethane, nitroethane, d-limonene and 3-methoxybutyl acetate is mixed to 1,1,1,3,3-pentafluorobutane to such an extent as not imparting any flammability. Also, propylene glycol based solvent(s) is mixed to 1,1,1,3,3-pentafluorobutane to such an extent as not imparting any flammability.