If the flammable gas supply cannot be shut off, the continued escape of unburned gas can create an explosive mixture in the air.

When sucked up by a whirl of air, this unburned gas travels up the core until it reaches a region where there is enough fresh, heated oxygen to set it ablaze.

The results illustrate that primary air ratio has a major effect on pulverized coal ignition and minor effects on gas temperature, oxygen concentration and unburned carbon at furnace exit.