Human and Organizational Factors (HOF) in ATEX Risk Assessment [Fattori umani e organizzativi nella valutazione del rischio ATEX]

ATEX (Explosive Atmosphere) risk assessment is required when any equipment or system could potentially cause explosive atmospheres. Despite many operations on plant and equipment containing dangerous substances are performed by operators, influences of human and organizational factor (HOF) are mostly not adequately considered during ATEX risk assessment. The integrated methodology here described (ATEX-HOF) is proposed to address two challenges: the identification and the quantification of HOF influence on ATEX risk assessment. The proposed methodology enriches the traditional ATEX risk assessment procedure, which consists of four steps: 1) Area classification, 2) Ignition source identification, 3) Damage analysis, and 4) ATEX Risk evaluation. ATEX risk assessment methodology is mainly semi-quantitative, while ATEX-HOF methodology provides a quantitative analysis for the Area classification and Ignition source identification, and a semi-quantitative approach for the Damage analysis. As a result, ATEX-HOF risk evaluation becomes more accurate. A probabilistic assessment based on event trees was introduced, taking into account both the technical barrier failure (Prtbf) and the human intervention in terms of Human Error Probability (HEP). The on-site application showed that taking into account HOFs could be particular important, especially for those companies where the safety culture is lower and consequently the usual hypothesis related to the correctness of the operator intervention (in maintenance, normal operations, and emergency) could bring to not conservative results.