The explosive dangers of dust and powders

In July 2015 an explosion at a wood mill is Bosley near Macclesfield killed 4 people. 

In subsequent investigations, the Health and Safety Executive implicated ‘Dust Issues’ as the cause of the explosion.

Aftermath of the dust explosion

The danger of explosive dust and fine powders is managed under the EU ATEX Directive which defines the classification of Zones where there is a risk of an explosive atmosphere.  In the UK, this legislation is embodied in the DSEAR Regulations, however the common practice is to use  ‘ATEX’ suffix to describe the UK rules too. 

Under ATEX/DSEAR, the zone classifications for gases, vapours and mists are Zones 0, 1 and 2. The equivalent for dust and powders and Zones 20, 21 and 22 

The Bosley incident highlighted a lack of widespread awareness of the risks surrounding dust accumulations in manufacturing and process environments at the time. This, despite existing ATEX regulations covering the risks.

While apparently innocent materials, dust and many fine powders, are intrinsically combustible. As a result, the danger exists across numerous industrial sectors including:

  • Food
  • Textiles
  • Metals
  • Chemicals
  • Pharmaceuticals

Since 2015 there has been a significant growth in understanding and awareness of the importance of managing dust and powders in industrial processes. Prevailing conditions can have a significant impact in these areas.

Ambient temperature is critical. Materials such as wood dust can release combustible gases when heated whilst particle size and volumes of powder/dust accumulation can lead to inherent risks.

Especially relevant is the nature of a dust-driven explosion. An initial (even minor) primary explosion may, in itself be containable. However, the blast shock can lift other dust accumulations into the atmosphere where they ignite from the heat of the primary explosion. Additionally, this secondary (and potentially larger) explosion can repeat in a chain reaction of explosions as more dust is shaken into the air and heated up again to a temperature at which it will explode. 

Managing Explosive Dust Risks

As with many other areas in manufacturing and process sectors, managing explosive dust risks combines good practice, training and housekeeping. Appropriate ATEX zone classification is vitally important. Correct ATEX zoning helps ensure that suitable safety processes and procedures are in place. In turn, these safeguard both staff and the production area. It’s also important from a commercial perspective as higher ratings will cost more to implement correctly.

Housekeeping is particularly important. Reducing or even eliminating the risk can be as simple as having an effective cleaning plan in place. Simply avoiding unnecessary build-up of dust can suffice. Consequently, combining good practice with effective training creates a solid platform for effective dust risk management.

Denca is finding ATEX zones 20/21/22 applying in an increasing number of projects where there needs to be consideration of dust-borne risks. 

To find out more, please contact us. 

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