At Hazardex Live 2025, Senior Consultant for TÜV Rheinland, Conal Brown, will argue that qualitative approaches are still relevant for risk assessment in a digital world, especially where there are substantial data gaps and uncertainties.

Engineers love numbers! We spent years at school, college and university learning how to manipulate them. Numbers give precision to our analyses and clarity to our thoughts. Machines love numbers too! Information about industrial facilities can be encoded into numbers and fed into Artificial Intelligence models to automate risk assessments and increasingly make decisions autonomously. Quantitative risk assessment and analysis may therefore seem like the future in a world of artificial intelligence tools and ubiquitous data.

A precise number, however, can mask significant uncertainties. In hazard and risk assessment it is critical to understand the uncertainties and other limitations associated with the information used in analysis. Otherwise, we may make decisions with either false confidence or undue conservatism.

This paper argues that there is still a place for qualitative methodologies in risk assessment, especially where there are substantial data gaps and uncertainties. In such a scenario, risk assessment is as much about the process of reaching consensus around uncertainty as it is about the final output. Better to have a qualitative assessment that is mutually understood to be only roughly right, than a quantitative one that is precisely wrong. Quantitative risk assessments are especially problematic when they are generated by ‘black box’ tools and the sensitivity of the result to uncertainties in the risk model and input data are poorly understood. Criticality and vulnerability assessment is used as an example to advocate for the continued relevance of qualitative approaches.

About the author:

Conal Brown is a Senior Consultant with TÜV Rheinland Industrial Services. He is an experienced practitioner involved in improving maintenance, reliability and integrity management for a wide range of companies across the chemical, oil and gas industries.