[VDI-Guideline-2263, Part 1]
A small heap of powder (length approx. 4cm, high approx. 1cm) is prepared inside a horizontal glass tube. The heap is then ignited at one end with a hot platinum wire (1000 °C).
The test is carried out in a hood with an airflow of approx. 0,2 m/s from the ignition point towards the heap.
The combustibility is observed and rated in combustion classes 1 to 6 as follows:
CC 1: no ignition (no spreading of fire);
CC 2: extinction after short burning (no spreading of fire);
CC 3: local burning or glowing, limited spread of the flame (no spreading of fire);
CC 4: Smoldering fire or slow flameless decomposition (fire spreads);
CC 5: complete combustion of the heap (fire spreads);
CC 6: very fast combustion or fast flameless decomposition (fire spreads).
In the plant substances with BC > 3 may form smoldering nests, e.g., after local ignition or overheating.
Substances with BC > 4 are candidates for classification as "flammable solids" according to the UN Recommendations on the Transport of Hazardous Goods. The burning velocity should be determined.
Substances with a low melting point very often show a higher combustibility index, if they are mixed with an inert solid, such a silica powder.
Depending upon the type of operation the combustibility at elevated temperature should be considered.