No. A safety integrity level is not directly applicable to individual subsystems or components. It applies to a safety function carried out by the E/E/PE safety-related system.

IEC 61508 covers all components of the E/E/PE safety-related system, including field equipment and specific project application logic. All these subsystems and components, when combined to implement the safety function (or functions), are required to meet the safety integrity level target of the relevant functions. Any design using supplied subsystems and components that are all quoted as suitable for the required safety integrity level target of the relevant functions will not necessarily comply with the requirements for that safety integrity level target. A simple example is when the subsystem or component is incorrectly installed.

Suppliers of products intended for use in E/E/PE safety-related systems should provide sufficient information to facilitate a demonstration that the E/E/PE safety-related system complies with IEC 61508.

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