Increase in use of hybrid hydrogen fuel cell and battery energy storage systems in modern energy applications brings significant safety challenges. The example of SIRIH₂ hybrid system combines hydrogen-based energy conversion with battery storage, creating a complex interaction between high-voltage components, control electronics, and management systems. Ensuring safe and reliable operation under both normal and fault conditions requires detail and structured approach to functional safety. This thesis focuses on a functional safety of the SIRIH₂ hybrid hydrogen fuel cell and battery system, with particular emphasis on the Battery Management System (BMS) as a safety-critical subsystem. The study applies the safety standards of IEC 61508 and ISO 13849 to identify hazards, assess risks, define safety goals, and assign appropriate Safety Integrity Level (SIL) and Performance Level (PLr) targets.