MINIMUN IGNITION TEMPERATURE (LAYER)
For the determination of the minimum ignition temperature of a 5 mm dust layer (also called smoldering or glow temperature) a layer of 5 mm thickness and with a diameter of 10 cm is prepared on a heating plate.
Then it is exposed during 2 h to a constant elevated temperature of the plate.
The smoldering/glow temperature is the lowest temperature of the plate, at which the layer ignites, smolders or self-heats to a temperature of 450°C (absolute) or 250°C (relative) above the temperature of the plate.
If none of these three conditions is met during four trials of 2 h each, the result for the plate temperature used is negative and the test is carried out at high temperatures.
The smoldering/glow temperature can only be determined for substances that do not decompose, melt or evaporate before smoldering.
The smoldering temperature of a given substance depends from its physical form, e.g., crystal form, particle size or bulk density.
For the determination of self-ignition temperatures of layers > 5 mm, heat accumulation tests in wire baskets are carried out.