Hatenkou Yuugi – Dust Explosions
Several unsavory characters are pursuing Rahzel, the main character of Hatenkou Yuugi. She has recently promised to refrain from using her magical powers for a week. While she could probably hold her own against one combatant, she doesn’t stand much of a chance against a group. Rahzel and her companion escape into a brewery where an idea strikes her. They smash open several containers filled with flour and other powdery substance. Then they hide in the wine cellar. When the bad guys arrive, they can’t see anything from all the powder, so one of them strikes a light. They die in a massive explosion. Rahzel offers an explanation, but it still leaves you wondering: Does this happen in real life?
Well there goes the neighborhood...
Yes, it does, and it’s actually a massive problem. OSHA and other safety regulating committees have continually written and revised standards for work areas producing large quantities of powder. All it takes is a large quantity of powder and an ignition source to have a spontaneous explosion capable of destroying entire facilities in the worst-case scenario. If you’re not familiar with this phenomena, you might be scratching your head right now. After all, flour and other powdery substances aren’t very flammable when sitting on your kitchen counter. It all has to do with the exposed surface area, which I’ll illustrate in a small math demonstration. 
You can see the difference pretty clearly. When all the boxes sit together, they form an n^2 function for surface area (n = number of sides). If you separate all of them, the function becomes n^3. The percentage difference between the two numbers steadily increases as you add more and more layers. Of course, powder doesn’t organize itself with anything resembling this uniform pattern, nor are they cubic particles, but you get the idea. With this knowledge, what determines whether a powder will burn or not?
We're going to make them an explosive treat!
You need oxygen for combustion. You can use another oxidizing agent, but oxygen is readily available and all around us. Now, when you set flour on the table, very little of its actual surface area is exposed. All the particles that form the top layer have half or less of their area exposed to oxygen, and there are thousands of particles who aren’t exposed at all. However, when you put the powder in the air, it doesn’t fall uniformly. All the particles separate. Suddenly, you have exposed the entire potential surface area to oxygen, and now it has enough oxygen to combust. As each particle catches on fire, it transfers heat to other particles in a quick and intense reaction. It doesn’t stop here though. The initial explosion can disturb powders at rest, kicking them into the air and causing secondary explosions. These related explosions usually cause the most damage in a dust explosion.
A chain reaction will trigger what he doesn't grab.
It doesn’t take much powder to cause an explosion either. For flour in particular, you only need 56 grams suspended in the air to cause an explosion covering a cubic yard. So, next time you walk into a room filled with powder, be wary. Otherwise, this might happen to you.
They're gonna have to glue you back together, in hell!
