LOPA is a semi-quantitative risk analysis technique. PI Asset Integrity Ltd use LOPA to evaluate risks with more rigour than basing it solely upon the qualitative approach.

By taking into account the fact that plants are protected by various layers of protection such as Pressure Relief Devices, Flare System, Fire Suppression System etc., Safety Integrity Level (SIL) ratings determined using the risk graph method (which inherently err on the side of caution) can be significantly altered confidently by using a more detailed analysis approach.