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.