Dr. Alfons Maier

Dust explosions –When the air catches fire

It is estimated that not a day goes by in Europe without a dust explosion. According to a current study from the United States, combustible dust represents a danger in any industrial facility – given an adequate concentration in the air and an ignition source. The explosive mix costs insurers millions of euros.

The fact is that the smaller the particles and the finer their distribution in the air, the greater the explosivity of combustible dust. The ignition source may be no more than a small electrical discharge triggered by a plug being removed from a socket or a hot metal component. Dust explosion is a familiar hazard particularly in the woodworking, metalworking, plastics processing, chemicals, paper, agricultural, food, and fodder industries. Precautions are taken to prevent such events from occurring, and many facilities go on producing for years and years without any mishap.

Statistics on dust explosion losses

In spite of all the precautions taken, the agricultural and food industries are particularly known for large losses and a certain loss frequency. Although large individual losses regularly occur in other industries, too, meaningful statistics are compiled and maintained only for individual fields or branches of these industries and only for individual countries. In most cases, it is almost impossible to compare these statistics because they draw on sources that differ in terms of the designation and composition of dusts, facility types, and ignition sources. In contrast, dust explosions in the agricultural sector and coal dust explosions – in the mining industry, for instance – are generally well-documented.

Dust explosions in the US agricultural sector

In the dust explosion statistics of the US agricultural sector there are records of

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  490 explosions from 1900 to 1956 with losses of US$ 70m,
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  192 explosions from 1957 to 1975 with losses of US$ 55m,
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  202 explosions from 1979 to 1988 with losses of US$ 169m,
• —
  106 explosions from 1996 to 2005 with losses of US$ 163m.

This averages out at about one event a month. The annual number of events ranges from six to 18, with individual loss amounts of between US$ 4m and US$ 56m.

The long-term trend that emerges in the agricultural sector is that dust explosions mainly occur in elevators (e.g. chain or bucket elevators operating as grain conveyors), fodder and flour mills, and silos.

Documentation of dust explosions in Germany

The institute for occupational health and safety of the German statutory accident insurance institutions has analysed 599 dust explosions that occurred in different sectors of industry over a period of about 25 years up to and including 1995.

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