This paper aims to show experimental research results of dust explosion of toner cartridges, and then propose countermeasure
way against such explosion. Toner is composed various materials, iron, carbon and other organic materials, and which sizes are
mostly less than 10μm (in diameter). Dust explosions sometimes occurred during usage, manufacture and recycled of toner
cartridges. And recently toner powder size becomes much smaller, and more danger of dust explosion. In Japan we experienced
incidents of dust explosion at toner cartridge manufacture and recycle facilities and other places. Therefore author studied its
danger of dust explosion using new and recycled toners with various dust explosion tests, such as the minimum ignition energy
test and the 30L explosion bomb test. Based on data, we found toner is safer than those of similar size of Al or Mg powder, but
have a potential like to most organic powder. To reduce ambient oxygen concentration at treatment equipment was one of
effective ways to reduce potential of dust explosion of toner cartridges.