4. Discussions and countermeasure
4.1. Danger of toner cartridge
Toner powder is not hazardous materials in the UN recommendations, not in the Japanese Fire Service law. We
regulated them as designated combustibles, which are less hazardous, in Japanese law.
Based on these data, it is clear that toner powder is easy to make dust explosion. Evaluation tests were also
conducted at the Research Institute of Safety and Engineering [4]. Sample powders were new and recycled toner
powder which was taken from the incident facilities in Hatano city, Japan. There is not large difference between
both samples, but recycled one might be much danger than new one in regard to lower limit of dust concentration.
In the near future, particle size will be smaller and will be more dangerous because of request for fine printing
technology. All samples we used, were for black. There consists of four colours (black, cyan, magenta, yellow), and
effects of colour difference was not studied in this paper because Yashima and Yamakuma reported there was no
difference in particle distribution and hazard [3]. We may study on this effect in the future.