The objective of the Traditional HAZOP study is (with collaboration of multidisciplinary team of employees of contractor) to identify potential hazards operability issues in process (Hazard and Operability Analysis) and to propose preventing actions. But there can be used also quantitative HAZOP study, which is able to estimate the risks in accordance to multi-factor Risk Assessment. The qualitative HAZOP analysis technique uses a systematic approach to identify possible deviations from normal operations and ensure that appropriate safeguards are in place to help prevent accidents with keywords for generating deviations from safe condition. Quantitative HAZOP is based on development of scenarios and finding the causes deviations, to identify safety functions and estimate the final effects, but it more complements the assessment of severity and probability of each scenario -it allows selecting the most important preventive recommendations for implementation.