To support the knowledge of specialists during a HAZOP brainstorming session, a support system, which is able to automatically generate a preliminary HAZOP report was developed. The support system, which is based on Coloured Petri Nets (CPNs), simulates the behaviour of the system when different abnormal scenarios occur. The research demonstrates that integration of CPNs and HAZOP is very effective to obtain a smart tool for risk assessment of complex systems, improving the HAZOP analysis procedures.