Table 1: Classification criteria of “three zones” in gob.

Criteria	Heat dissipation zone	Oxidation zone	Choking zone
Oxygen concentration/%	>18	18-10	<10
Ventilation leakage velocity/m s-1	>0.004	0.004-0.00167	<0.00167
Temperature rising rate/°C d-1	The temperature rising rate is not less than 1°C per day in the gob, then it is considered that the gob is in the oxidation zone.