The application of a hand-made air GM counter as a training material is presented based on evaluation by 16 participants of a workshop by International Atomic Energy Agency (IAEA) technical cooperation programme (TCP) project RAS0079, held in Japan in 2019. A questionnaire survey was administered to evaluate the attributes of the device as well as each respondent’s self-assessment of their level of understanding and ability to communicate associated content. The performance of participants in the lecture tests related to the device was also analyzed. The device had an overall effectiveness rating of 8.3/10 with all attributes above 8/10. The respondents’ level of understanding and ability to communicate was significantly different before and after using the device. The study also revealed some knowledge deficiencies that can be addressed by using such simple
devices and may need more attention for future teacher training programmes.