A Safety Integrity Level (SIL) assessment determines the effectiveness of safety systems based on the probability of tolerable incidents that can occur within a number of processing demands. In land-based industry, as well as in offshore process plants, safety instrumented systems are applied in order to maintain the risk at an acceptable level. The performance of the instrumented protections is crucial for achieving the necessary risk reduction. The basic concept is to provide a risk-based approach for determining the required performance of safety related systems. This implies that requirements to a safety function should be based on the actual risk picture for the protected equipment, process unit or similar.