The industrial gases industry originated in 1886, when a London-based company began producing high-purity oxygen. Initially, purified oxygen was a solution in search of a problem, but demand for it soared early in the twentieth century with the emergence of welding technology. By then, dramatic technological improvements in air separation and purification had emerged, as had most key firms dominating the industry today. Building on air in the decades that followed, the firms expanded their product range and geographical reach to create applications that were essential to every manufacturing process in the modern world, from semiconductor production to oil refining, waste water treatment, and steel-making. This is the first scholarly history of this vital but invisible industry from its origins to the present. Based on unparalleled access to company and public archives, the book explores business and technological development, industrial evolution, and the industry’s local roots and international and global reach.