Flat-pressed or moulded panels manufactured from particles of wood or other ligno-cellulosic materials bonded by a suitable, usually organic, binder in the presence of heat and pressure. They may also be manufactured by extruding the materials into a mould under heat and pressure. Extruded particle board may be solid or with hollow cavities. The density of particle boards varies with the density of raw materials used and the binder, pressures and temperatures used in manufacture. It includes special types of particle board as waferboard and oriented particle board. It excludes wood wool board or other boards with mineral binders.