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Determination of Dust Explosion Parameters

In accordance with the specification R 003 6/2000 of the Chemical Industry Trade Co-operative Association, a 20 l dust explosion sphere or a 1 m³ vessel serves as a standard laboratory apparatus which is suitable for examining explosive gases, fumes and dusts. The maximum operating pressure is 25 bar. The following parameters, among others, are determined in this sphere:

  • Maximum explosion pressure
  • Maximum speed of pressure increase
  • K values for division into explosion classes
  • Explosion limits
  • Oxygen limit concentrations

In connection with dust explosions the maximum pressure pmax and the maximum pressure increase over time (dp/dt)max are determined for the explosion of a dust/air mixture in closed vessels at optimum concentration.

A dust in the respectively examined form (e. g. grade, humidity) is not explosive when no ignition occurs over a wide range of concentration (at least 30–2000 g/m³).

A material can only be classified as "non-dust-explosive" if exothermal oxidation reactions can be ruled out by its chemical characteristics or if the examinations of the explosiveness have not led to an explosion either for fine dust (< 63 µm).

The maximum pressure increase over time is volume-dependent. The product of the maximum pressure increase over time and the cubic root of the volume concerned is constant (cubic law) and is known as the KSt-value.

Different explosion classes can be defined for combustible dust based on this:


KSt-Wert Staubexplosionsklassen
< 200 bar m s-1 St 1
< 300 bar m s-1 St 2
> 200 bar m s-1 St 3





The dust explosion class only gives a recommendation for which protection concept or what constructive explosion protection measures are to be applied in connection with dust explosions.