Students of chemistry should achieve certain safety competencies. Among other things they should be able to learn from undesirable events that happen during their work. In order to facilitate this we decided to analyze, together with our students, the specific causes of a few undesirable events which have happened in our school laboratories. We applied an approach based on root cause analysis and on the classification of four levels of safety assurance. Our examples showed the effectiveness of this approach, leading us at once not only to the identification of errors committed by students, but to those of teachers as well. This enabled us to compile a set of recommendations for the possible prevention of such incidents. Above all, our analysis strongly reinforced the conviction that this approach - learning from actual incidents - is more than just a cause analysis technique. It is a pattern of behavior, a cultural pattern. A technique may be analyzed and taught, but the most effective way to pass on a behavioral pattern is to set an example. The best way to show students how to learn from their own errors is for teachers to demonstrate how they have learned from their own experiences. Work in chemistry labs provides ample opportunities for this. (C) 2010 Elsevier Ltd. All rights reserved.