At the Belgian Nuclear Research Centre (SCK CEN) more than 850 employees advance the peaceful applications of ionising radiation through research, services and education and training. Several initiatives are taken to guarantee a safe working environment, one of them being a compulsory introductory safety training for all new employees, followed by refresher courses. With the objective to increase the flexibility for the participants and to optimise the teaching time of lecturers, the training format is adapted from face-to-face training to blended learning in which a significant amount of online learning is introduced. To appraise the perception and effectiveness of the original face-to-face training and the newly developed e-learning modules, and to compare both, information is gathered on two levels. Firstly, to monitor the perception of the participants regarding the face-to-face and e-learning formats an online questionnaire was launched. Secondly to evaluate the knowledge gain (difference between pre and post-test results), the participants were requested to answer the same set of technical/scientific questions before and after the training. Results of the perception study show that the e-learning format was well received by the learners. For both learning formats an overall knowledge gain was noticed. The highest knowledge gain was noticed for the e-learning format. The results on perception and effectivity of the e-learning format confirm the further use of this format.