Why is the freezing station made of incombustible materials?

Prevent fire. According to Article 47 of "Coal Mine Safety Regulations", in order to prevent the occurrence of fire, the freezing station must be built with non-combustible materials and equipped with ventilation devices, and the ammonia concentration in the air in the station should be measured regularly, and the ammonia concentration should not be greater than 0.004%. Fireworks and firecrackers are strictly prohibited in the station.