The standard regards the legend (wording on marker) to be the primary means of identifying the content of the pipe. The marker should give the name of the contents of the pipe in either the full name or abbreviated form. Arrows are also required to indicate the directional flow of the contents. Legends should be brief, pointed, and simple for greatest effectiveness. Contents should be identified with sufficient additional details such as temperature, pressure, etc., as are necessary to identify the hazard. Legends should be applied close to valves or flanges and adjacent to changes in direction, branches and where pipes pass through walls or floors; and at intervals on straight pipe runs sufficient for identification.