Automation offers the possibility of building production systems more and more complex. This evolution leads to a modification of human operator’s activities which sets out problems, particularly when a failure occurs in the process. The first part of the paper presents, after the human operator’s work and manmachine interfaces in a supervision room, a synthesis of different problems linked to alarms. The second part of the paper is a proposal to design and to treat alarms. The goal is to design and display “educational” alarms, well defined and well treated, giving to the human operator the means to perform correctly his work. On that subject, the Multilevel Flow modelling (MFM) for the functional analysis and methods from the dependability science like FMEA (Failure Mode and Effects Analysis) are interesting.