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Explosive suction media properties

Minimum Ignition Energy

Minimum Ignition Energy MIE

  • Smallest energy that is required for the ignition of the explosive atmosphere

Minimum Ignition Temperature MIT (explosive atmosphere)

  • Relevant for the maximum equipment surface temperature

Minimum Glow Temperature (only for dust layer)

  • Relevant for the maximum equipment surface temperature



A basic classification can be made in order to decide about suction system specification as follows:

A Standard :

MIE > 10 mj

ST Class 1 or 2

B Specific :

MIE 3-10 mj

ST Class 1 or 2

C Extreme :

MIE 1 - 3 mj

ST Class 1 or 2 or 3

D Highly reactive:

MIE < 1 mj

ST Class 1 or 2 or 3


The Kst value is calculated as the equivalent pressure in a 1 m3 sphere from the cube law (Kst value = cube root of volume x explosion pressure rise).

The ST class is based on the Kst value as follows:
ST class 0 - Kst value = 0
ST class 1 - Kst value less than 200 bar m/sec
ST class 2 - Kst value between 200 and 300 bar m/sec
ST class 3 - Kst value greater than 300 bar m/sec

Explosion testing for Kst value & Pmax is essential to validate protection design (explosion venting, explosion suppression and explosion containment). Results of testing from our database for common dusts are shown in the table below.


Kst, Pmax & ST class test results table

Grain dust 89bar.m/sec 9.3bar g ST1
Coal dust 85bar.m/sec 6.4bar g ST1
Flour 63bar.m/sec 9.7bar g ST1
Sugar 138bar.m/sec 8.5bar g ST1
Wood dust 224bar.m/sec 10.3bar g ST2
Aluminium dust 515bar.m/sec 11.2bar g ST3
Sewage sludge 102bar.m/sec 8.1bar g ST1
GRP dust 216bar.m/sec 7.6bar g ST2