[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.