Influence of size and shape of magnesium dust, inert component in the dust (particle) and moving velocity of magnesium dust cloud on the magnesium dust explosion, and explosion index, both volume and surface resistivities for electrostatic safety, detection of igniting spark to prevent the explosion, etc. were studied. Larger dust required larger ignition energy and fibrous (flake) dust was hard to form explosive dust cloud. Inert components in material contributed to suppress explosive character basically but too much of the component (Ca) could not be blended because of casting characteristic, thus making inert component (Ca : about 1 wt%) ineffective to reduce the magnesium explosibility. The dust cloud was not ignited when the dust cloud moved fast (over about 4 ms-1). The Kstvalue was 321 [×102 kPa•ms-1], showing extremely strong explosion severity. Monitoring a spark could be practical to assess the ignition risk of the dust cloud. The volume resistivity was 6.5×109Ω•m and surface resistivity was 8.3×1011Ω, indicating slightly poor conductive characteristic.
マグネシウム材料の利用に伴うマグネシウム粉じん爆発災害の防止に関し，マグネシウム粉じんの粒度と形状，含有不燃物質（Ca），および粉じん雲の流動速度が爆発に及ぼす影響，爆発指数を調べ，静電気災害の見地から体積固有抵抗と表面固有抵抗，着火源となりうる火花の検知等を検討した。これらの実験結果より，粒度の増大に伴い，着火エネルギーが大きくなること，繊維状の粉じんは爆発性粉じん雲の形成が困難であること，不燃物質（Ca）の含有率１％では爆発抑制が困難であること，粉じん雲の流動速度が約４ms-1程度以上では着火しないこと，爆発指数は321［×102kPa・ms-1］でマグネシウム粉じんは激しい爆発性を有すること，体積固有抵抗は6.5×109Ω・m，表面固有抵抗は8.3×1011Ωで，導電性はやや弱いことなどが明らかになった。
magnesium, explosion, spark, ignition