A form of semi-quantitative risk analysis used for a process or system that analyses individually the different forms or layers of protection; it is used to reduce or mitigate process risk in terms of reducing the likelihood of the occurrence of an undesirable event or reducing its severity. LOPA is used to determine and understand the safety integrity level (SIL) and is a widely used technique in the oil and gas industry. It uses various hazard analysis techniques and evaluates the frequency of potential incidents as well as the probability of failure of the layers of protection.