Accidental chemical poisoning causes more than 35 000 child deaths every year across the world, and it leads to disease, disability, and suffering for many more children. Children's ignorance of dangers and their failure to interpret hazard warning signs as intended contribute significantly to this problem. A new Globally Harmonized System for Classification and Labeling is being implemented internationally with a view to unifying the current multiple and disparate national systems. This study was designed to establish a productive, effective means of teaching the new GHS warning signs to primary school children (aged 7-11 years). A pre-test, post-test, follow-up test design was employed, with a teaching intervention informed by a Delphi survey of expert opinion. Children from one school formed the experimental group (n = 49) and a second school provided a control group (n = 23). Both groups showed a gain in knowledge from pre-test to post-test, the experimental group with a larger gain but which was not statistically significant. However, longer-term retention of knowledge, as shown by the follow-up test, was statistically significantly greater in the experimental group (p = 0.001). The employment of teaching to match children's preferred learning styles, and the use of active learning were found to be related to improved retention of knowledge. Part of the study involved eliciting children's interpretation of standard hazard warning symbols, and this provoked considerable concern over the potential for dangerous misinterpretation with disastrous consequences. This article focuses on the reasons for such misconception and the action required to address this successfully in testing the intervention.