so on. An example of a product classified according to its form is personal hygiene soap. When in the form of a bar, cake or moulded shape, such soap is classified under subheading 3401.11, which provides for Soap and organic surface-active products and preparations, in the form of bars, cakes, moulded pieces or shapes, and paper, wadding, felt and nonwovens, impregnated, coated or covered with soap or detergent: For toilet use (including medicated products). Conversely, liquid personal hygiene soap is classified under either 3401.20, which provides for Soap in other forms, or 3401.30, which provides for Organic surface-active products and preparations for washing the skin, in the form of liquid or cream and put up for retail sale, whether or not containing soap. An example of a product classified according to its function is a carbon monoxide (CO) detector. If the CO detector captures and displays gas measurements, then it is properly classified under subheading 9027.10, which provides for Instruments and apparatus for physical or chemical analysis (for example, polarimeters, refractometers, spectrometers, gas or smoke analysis apparatus; instruments and apparatus for measuring or checking viscosity, porosity, expansion, surface tension or the like; instruments and apparatus for measuring or checking quantities of heat, sound or light (including exposure meters); microtomes. Gas or smoke analysis apparatus. If the CO detector does not capture and display gas measurements, then it is properly classified under subheading 8531.10, which provides for Electric sound or visual signaling apparatus (for example, bells, sirens, indicator panels, burglar or fire alarms), other than those of heading 85.12 or 85.30. Burglar or fire alarms and similar apparatus. Although every product and every part of every product is classifiable in the HS, very few are explicitly described in the HS nomenclature. Any product for which there is no explicit description can be classified under a "residual" or "basket" heading or subheading, which provide for Other goods. Residual codes normally occur last in numerical order under their related headings and subheadings. An example of a product classified under a residual heading is a live dog, which must be classified under heading 01.06, which provides for Other live animals because dogs are not covered by headings 01.01 through 01.05, which explicitly provide for live equine, live bovine, live swine, live sheep and goats, and live poultry, respectively. Applications As of 2015, there were 180 countries or territories applying the Harmonized System worldwide, HS