As an essential component of a CCD, Integrity operating windows (IOW’s) are gaining recognition as a valuable input into a corrosion control document. What are IOWs? The American Petroleum Institute (API) has a new recommended practice in the ballot stage (API RP 584) that discuss the need to establish operating limits that address the controls necessary for process variables that might affect the integrity or reliability of the process unit. An example of an IOW is the establishment of furnace tube temperature limits to avoid premature rupture. At some established limit, say 800F, a furnace tube designed for 775 F would have a shortened service life, so operators would understand the need to maintain control of furnace firing to remain below the 775F limit. That limit of 775F would be an IOW limit for the furnace tubes.