Guidelines for Enabling Conditions and Conditional Modifiers in Layer of Protection Analysis - CCPS (Center for Chemical Process Safety) - Bog

The initial Layer of protection analysis (LOPA) book published in 2001 set the rules and approaches for using LOPA as an intermediate method between purely qualitative hazards evaluation/analysis and more quantitative analysis methods. Basic LOPA provides an order-of-magnitude risk estimate of risk with fairly reproducible results.