A welder was killed while welding on a wastewater recovery tank. He had been welding a pipe onto an empty 55-foot (16.7-meter) tank. Residual material inside the tank ignited and the tank exploded. When emergency workers arrived, they found his body outside the building, across the road. A competent person should inspect all hot worksites and test conditions inside containment vessels before welding starts. Structures contaminated with organic materials should never be inerted with steam. Even if you won't be in this particular situation, learn to recognize and avoid hazardous situations.