Process facilities should be designed as far as possible to be inherently safe. Inherent safety involves reducing hazardous inventory and making the process mechanical design sufficiently robust.
However, it is not always possible to reduce risk to tolerable levels by inherent safety measures. Where further risk reduction is required, protection layers will be needed to prevent incidents propagating into accidents. Mitigation layers will be needed to minimise the consequences of hazardous failure events. LoPA provides special rules for protection layer credit which, when applied correctly, should ensure that adequate risk reduction is applied in the design.