What is a Safety Integrity Level (SIL) target and how is it determined?

• A. A label for the physical dimensions of a robot
• B. A measure of the required reliability of a safety function; determined by risk assessment and required risk reduction
• C. A price indicator for safety components
• D. A temperature rating for control units

Answer: (B)

A Safety Integrity Level target expresses how reliable a safety function must be to reduce risk to an acceptable level. It’s not about physical size, cost, or temperature. The target comes from a risk assessment: you identify hazards, evaluate how serious the harm could be, how often people might be exposed, and how effectively existing safeguards reduce risk. Based on what residual risk you’re willing to accept, you set an SIL level that will provide the needed reliability—often described in terms of required probability of failure on demand or similar reliability metrics. Once the SIL target is set, you design, implement, and verify the safety function to meet that level, using appropriate architecture, diagnostics, testing, and proven components.

So, the correct choice captures that the SIL target is about the required reliability of a safety function determined by risk reduction needs. The other options describe physical dimensions, price indicators, or temperature ratings, which do not relate to how safely a function must perform.