Tehran University of Medical Sciences International Journal of Occupational Hygiene 2008-5109 5 3 2015 10 11 101 108 EN MOHAMMAD JAVAD JAFARI Department of Occupational Health Eng, Faculty of Health, Shahid Beheshti University of Medical Sciences, Evin, Chamran freeway, Tehran, Iran. SHIMASADAT LAJEVARDI Department of Environment and Energy, Islamic Azad University, Science & Re-search Branch, Simon Bolivar Blvd, Poonak, Tehran, Iran. IRAJ MOHAMMADFAM Department of Occupational Health Eng, Faculty of Health, Hamadan University of Medical Sciences, Hamadan, Iran. 2015 10 10 2015 10 10 The safety of hydrogen generation facilities is the main concern in their process operation. This study was conducted to identify the hazards and evaluate the risks of a hydrogen generation plant. For this purpose, PrHA (Process Hazard Analysis) was applied for hazard identification while LOPA (Layer of Protection Analysis) was used for risk assessment. The study was conducted in the hydrogen production unit of Behshahr Industrial Complex, Iran in 2011 and 2012. In the process of risk assessment, the records of the accidents and plant flow diagrams were studied. Then, the knowledge of the experts and operators were used through brainstorming prior to the application of LOPA technique. LOPA standard template was applied using PHA-Pro6 software. The initiating events, consequences, independent protection layers and probability of failure were determined for 16 scenarios in 7 nodes. The results showed that without the application of IPLs, the risks of 2 scenarios needed immediate action, 9 scenarios required action at next opportunity and 5 scenarios were operational. The application of IPLs would significantly decrease the risks. The study concluded that LOPA has sufficient credibility for semi quantitative risk assessment of high potentially hazardous plants. https://ijoh.tums.ac.ir/index.php/ijoh/article/view/75 https://ijoh.tums.ac.ir/index.php/ijoh/article/download/75/75