Self Heating Testing of Dusts

“Spontaneous ignition” is a term that refers to the ignition in the absence of an
obvious ignition source. Such events can occur through a process called self
heating. An example of a common failure scenario due to self heating occurs
where dusts accumulate in deep layers in heated locations such as inside a
multi-pass web dryer. While the dryer temperature is nominally at a temperature
believed to be too low to cause ignition, an exothermic decomposition process
can occur within the mass of accumulated dust. The dust mass is thermally
insulating and, thereby, prevents escape of heat generated by the decomposition
process. The result is a rise in temperature within the dust mass to a level well
above the external temperature eventually leading to ignition.

Evaluation of the self heating tendency of dusts is conducted in accordance
with the procedure recommended but the U.S. DOT Packaging Classification
Test  as described in 49CFR173.125 Appendix E. 

For this procedure, dusts are normally tested in their 'as supplied' form.

Sample size: 2,500 g