In addition to fires, buildings, especially industrial buildings, are also haunted by another risk, namely explosions. There are various types of explosions that can occur in a building, depending on what components are contained in the building. Previously we have discussed Aerosol Explosion, one of the explosions that is rarely discussed by the public. This time, we will discuss the types of explosions that are often overlooked or underestimated because of their very small trigger when viewed with the naked eye – dust. Yes, this time we will discuss Dust Explosion.

Fire vs. Explosion

Technically, the difference between fire and explosion can be seen from the processes and components that support the occurrence of these two events. Judging from the process, fires occur due to the exothermic chemical reaction of the combustion process where oxidation occurs. In fires, there is usually a gradual process of energy release. On the other hand, explosions occur as a result of the release of energy that has previously accumulated and been suspended. Compared with fires, explosions occur rapidly. A fire does not necessarily result in an explosion, and an explosion can occur in the absence of a fire.

Apart from the process of releasing energy, the difference between fire and explosion can also be seen from the components involved when these two events occur. This can be seen through the fire triangle and the explosion pentagon.  The fire triangle explains that fires can occur due to the following three components: heat, oxygen, and fuel.  The pentagon explosion adds two components to the fire triangle. The two components are confinement and dispersion.

About Dust Explosions

According to the National Fire Protection Association (NFPA), combustible dust is a finely divided combustible particulate solid, which poses a flash fire or explosion hazard when suspended in air or a process-specific oxidizing medium at a certain concentration range. The occurrence of dust explosions can also be explained through the explosion pentagon. According to this model, dust explosion can occur if there are the following five components: combustible dust, oxygen, confinement of dust clouds, heat/source of fire (ignition), and dispersion of dust particles.

To understand the dust explosion more easily, let's consider the following example. Suppose we have flour, and this flour is exposed to a source of fire, we can start a fire at the top of the pile of flour because it is where the surface area of the flour interacts and reacts with oxygen. Still with the same flour, if we spread it in the air, we can get a flash fire. Now, if we spread the flour inside a closed space, we get confinement. Exposure of confinement of dust cloud to heat/fire sources causes the pressure on the enclosed space to increase. At some point, the pressure becomes so great that it exceeds the maximum pressure that a closed space can bear, and an explosion occurs.

We need to remember that combustion can occur only on the surface of a solid or liquid object. With the same mass, dust of a smaller size will result in a larger area. The larger the total area, the faster the dust burns and the explosion is also greater.

Flammable Dust

Flammable dust can include:

• most solid organic matter (flour, sugar, wood, grains, etc.)

• carbon-containing materials (charcoal, soot, etc.)

• textile fibers

• some inorganic nonmetallic materials

Flammable dust is usually produced from flammable materials as well. However, not all flammable dust comes from combustible materials. Some of the materials already mentioned above are "usually" not flammable but can burn or even explode if the particle size and concentration are right.

Therefore, any activity that generates dust must be analyzed to see the risk that the dust produced is flammable dust and can cause a dust explosion. Dust can collect almost on all surfaces of objects or equipment. If it turns out that there is a potential for a dust explosion, even a very small buildup of dust can cause serious damage.