Sustained combustility


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Sustained combustility (UN Test L.2)

Flammable liquids with a flash point in a closed crucible of ≥ 23 °C and ≤ 60 °C must always first be classified in UN Packing Group III for Class 3 as defined in UN transport regulations and in Category 3 as defined in the GHS and CLP Regulation (EC) No. 1272/2008, as well as marked with the signal word “Warning” and the hazard warning “H226: Flammable liquid and vapor”.

Such liquids may however be exempted from this classification if they have a flash point of > 35 °C and if they do not sustain spontaneous combustion in any way. For this purpose, a negative sustained combustibility test (UN Test L.2) as defined in DIN EN ISO 9038 is required.

This test examines whether, at certain test temperatures (60.5 °C and 75 °C) and under defined test conditions, a flammable liquid forms sufficient vapor to sustain spontaneous combustion after ignition by an ignition source (propane gas flame) and removal of this ignition source.

A pipette is used to introduce 2 mL of liquid into the test device’s heatable sample well, which is made from corrosion-resistant metal. The test substance is then brought to the specified temperature (60.5 °C or 75 °C) within a temperature-adjustment time of 60 ± 2 s. If the liquid has not yet ignited, the gas flame is moved to the test position above the edge of the liquid surface and the flame is held in this position for 15 seconds. Meanwhile, the behavior of the test substance is observed.

If no sustained combustion is observed during the temperature stabilizing time or after application and removal of the test flame, the test is repeated at a reduced temperature-adjustment time of 30 ± 1 s.

If no spontaneous sustained combustion occurs either during temperature adjustment or when the test flame is applied, the test substance is classified as not sustaining combustion and may therefore be excluded from the classification.

However, the test substance should be classified as sustaining combustion if one of the following reactions occurs during any of the tests performed:

(a) the test portion ignites during the temperature-adjustment time

(b) the test portion ignites while the test flame is in the test position and is held there for 15 s, and sustains combustion for more than 15 s after the test flame is returned to the “off” position.

Intermittent flashing lasting less than 15 s should not be regarded as sustained combustion.

Normally,  at  the  end  of  15  s,  the  combustion  has  either  clearly  ceased  or  continues. In case of doubt, the product is to be classified as sustaining combustion.

DIN EN ISO 9038: Test for sustained combustibility of liquids