Identifying the detrimental effect of environmental factors and subsystem interactions are one of themost challenging aspects of early hazard assessment in the design of complex safety critical systems.Therefore, a complete understanding of potential failure effects before the catastrophe happens is a verydifficult task. The thesis proposes a model-based hazard analysis procedure for early identification ofpotential safety issues caused by unexpected environmental factors and subsystem interactions within acomplex safety critical system. The proposed methodology maps hazard and vulnerability modes tospecific components in the system and analyzes the hazard propagation paths for risk control andprotection strategies. The main advantage of the proposed method is the ability to provide the designerswith means to use low-fidelity, high level models to identify hazardous interactions. Using thistechnique, designers can examine the collective impacts of environmental and subsystem risks onoverall system during early stages of design and develop a hazard mitigation strategy.