Integration of HOFs into ATEX Risk Assessment Methodology

The current ATEX (Explosive Atmosphere) risk assessment methodology relies on a semi-quantitative approach based on the following indexes: probability of an explosive atmosphere formation, probability of the presence of an effective ignition source and consequences. The whole risk assessment procedure can be separated into four steps - area classification, ignition sources identification, consequence analysis, and risk evaluation. However, when reviewing the whole ATEX risk assessment procedures and their results, despite many operations on plant and equipment containing dangerous substances are performed by operators, the human and organizational influences are neglected. The study proposed in this paper is to develop an ATEX risk assessment methodology with the integration of human and organizational factors (HOFs), in order to provide an advanced methodology able to analyse the HOFs influences on ATEX hazards. The developed ATEX risk assessment methodology introduces in the procedure the Technique for Human Error Rate Prediction (THERP) to identify human and organizational weaknesses, and also provides a tool for calculating the human error probability (HEP) in the first two risk steps - area classification and ignition sources identification. During the risk evaluation procedure, human risk level, based on the results of HEP, has been introduced into the original ATEX risk assessment methodology.