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Why do flour particles explode when they reach a certain concentration and encounter a trace of open flame?
Explosion accidents caused by flour often occur, generally in flour processing plants with limited environment and small restaurants with small space. The particle size of flour is very small, which is dispersed in the air and reacts with oxygen very quickly, which is the cause of the explosion.

Flour explosion is only a kind of dust explosion. Dust explosion refers to the violent explosion caused by combustible dust (flour, pulverized coal, etc.) or dust (aluminum powder) that can react with oxygen more rapidly and spread in the air more evenly, and there are factors such as open flame, high temperature and electric spark that stimulate chemical reactions such as combustion to occur rapidly.

For the convenience of eating and processing, flour particles are generally very small. If it is dispersed in the air, it is full of sufficient oxygen around the flour. When it meets an open flame, the flour will burn rapidly under the supply of sufficient oxygen, and it will continue to cause the burning of the flour floating around, forming a rapid chain reaction, generating a lot of heat in a short time, which makes the gas in the space expand rapidly, thus forming an explosion. Moreover, the smaller the particle size of flour, the more quickly the flour can be burned and the explosion will be more violent. In some small restaurants with limited space, sometimes there are explosion accidents caused by dumping flour beside an open flame.

Dust explosion usually occurs in the air. The explosion limit has an upper limit and a lower limit. The upper limit refers to the highest concentration where dust explosion may occur. When it is higher than this concentration, combustible dust robs oxygen, and it is difficult to form full combustion, and the effect of heat generation is limited. Moreover, the combustion of oxygen in the air is more limited, which makes it difficult to cause an explosion. The dust concentration below the lower explosion limit is too dispersed, so it is difficult to form a chain of dust combustion and explosion.

The ignition point of flour is lower than the temperature of flame, so if the concentration of flour in the air is between the upper limit and the lower limit, as long as there is an open flame, it will cause rapid flour combustion, and the environment is relatively limited, and the result of rapid gas expansion is explosion. Moreover, dust explosions often occur many times because the dust aroused by the first wave of explosions explodes again.

Dust explosions often occur in many industrial places. In order to protect workers' health and life safety in modern times, it is generally necessary to set up dust removal measures in the workplace, on the one hand, to prevent workers from inhaling too much dust and causing lung diseases, on the other hand, to prevent dust explosions and other events.