One of the most dangerous aspects of working in an iron mill is the potential exposure to various hazardous gases. In many blast furnaces, a mixture of natural gas and recycled furnace gases are transported and burned in order to generate heat. These gases are invisible and while they have a scent, this smell is the same smell most furnaces give off normally as they operate. Men working near the furnaces could enter into pockets of gas without realizing it and quickly be cut off from oxygen. A major gas leak could have the potential to harm or kill dozens of people. By the 1940s different oxygenation equipment was regulalry being used in blast furnaces, like the kind the men pictured are wearing while doing repairs. However, gas leaks remained a major issue well into the decline of steel in the 1970s and 1980s, and continue to be a danger to this day.