Mo. Rev. Stat. § 293.410

In coal mines welding and cutting with electricity or flame shall be restricted to places where trolley locomotives are permitted to operate. Where it is necessary to do welding and cutting in face regions, perceptible ventilation is required, and such work shall be under the direct supervision of a mine official, who shall test for explosive gas before starting operations and frequently thereafter. In all welding and cutting operations, precautions shall be taken against starting a fire, and the area shall be rock-dusted.