This standard is the same as IEC 61511 only. All of the text of IEC 61511-1 (2003) has been retained, but deviations are shown by strikeout and added parts are indicated by putting underline below the added text in the standard. One of the major additions into this standard with respect IEC 61511, is Clause 1, “for existing SIS designed and constructed in accordance with codes, standards, or practices prior to the issue of this standard (e.g., ANSI/ISA-84.01-1996), the owner/operator shall determine that the equipment is designed, maintained, inspected, tested, and operating in a safe manner.” This clause is similar to one contained in ISA S84.10-1996. This popularly referred to as Grandfather clause (in the previous paragraph, a portion of the write-up is shown in italics as is found in the original standard to indicate some addition from IEC 61511). This will be clear from the following figures which actually are from IEC 61511, but when used in ISA there are some changes in Fig. VI/6.0-1B, where IEC 61511-1 has been struck off (not shown here), and ANSI/ISA reference has been put in. In order to bring these to reader's notice, this figure has been placed under this standard.