Section 18 Optical, photographic, cinematographic, measuring, checking, precision, medical or surgical instruments and apparatus; clocks and watches; musical instruments; parts and accessories thereof 90 Optical, photographic, cinematographic, measuring, checking, precision, medical or surgical instruments and apparatus; parts and accessories thereof 90 27 Instruments and apparatus for physical or chemical analysis, etc 90 27 10 Gas or smoke analysis apparatus 90 27 10 00 Gas or smoke analysis apparatus Commodity Code Description 90 27 10 00 000 Gas or smoke analysis apparatus