Emergency response is only ever effective if potential, credible emergency incidents are pre-planned and exercised. There is a need for effective response training that considers the site specific incidents that could occur and provides responders with a clear view of the scenario. How is it possible to estimate the performance of an Emergency Response System (ERS)? This paper resumes the past experience on the inspections and audits of ERS carried out and discuss about the weak points met to achieve an effective response in case of emergency.