A Study on Preventing Spontaneous Combustion of Residual Coal in a Coal Mine Goaf

Table 2

Chinese safety standards for divided goaf zones [8].

Zone	Oxygen concentration	Airflow velocity	Temperature gradient
Radiating	—	m/s	—
Oxidized	O2 ≥ 8%	0.02 m/s ≥ ≥ 0.001 m/s	> 1°C/day
Asphyxiation	O2 < 8%	m/s	—