Which condition makes a solid fuel most hazardous?

Which condition makes a solid fuel most hazardous?

• A. Turnings or ribbons
• B. Powder or dusts
• C. Shredded materials
• D. Large blocks

Answer: (B)

Fineness of the material drives how hazardous it is. When solid fuel is in powder or dust form, it can become airborne and mix with air to create a combustible cloud. That cloud can ignite and, in confined spaces, propagate rapidly enough to cause a dust explosion. The large surface area of fine dust makes ignition much easier and the reaction much more vigorous than with other forms. Turnings or ribbons and shredded materials are still solid pieces and burn, but they don’t form the uniform, explosive dust cloud as readily as powders. Large blocks have the smallest surface area relative to mass and burn slowly, without producing the rapid, explosive pressure rise seen with dust clouds. So the key idea is the ability of powder or dust to form an ignitable, ventilated cloud that can explode.

Fineness of the material drives how hazardous it is. When solid fuel is in powder or dust form, it can become airborne and mix with air to create a combustible cloud. That cloud can ignite and, in confined spaces, propagate rapidly enough to cause a dust explosion. The large surface area of fine dust makes ignition much easier and the reaction much more vigorous than with other forms.

Turnings or ribbons and shredded materials are still solid pieces and burn, but they don’t form the uniform, explosive dust cloud as readily as powders. Large blocks have the smallest surface area relative to mass and burn slowly, without producing the rapid, explosive pressure rise seen with dust clouds. So the key idea is the ability of powder or dust to form an ignitable, ventilated cloud that can explode.