Causes of releases considered in traditional QRA are usually mechanicalfailure and not this type of events. They further concluded that mainhazards not included in QRAs too, are those occurring in abnormal situations and not in the normal continuous operation. Also, not includedare non-mechanical wear failure modes of equipment, such as thosecaused by human error, or rather human variability, and overload.(Here should be noted that the OREDA (2009) database often takesthose factors into account). The same of not being included is true formaterial reactive hazards causing runaway reactions, which are knownas possible. Likewise, HAZOP does not take into account detailed effectsof external threats as storm, flooding, lightning, and cyber-attack.Usually in QRAs only mitigation barriers are considered and not thepossible failure of preventive barriers. A reason may be that HAZOPresults are not available in the early stages of design