In 1941, the Montreal-based Canadian Liquid Air Company (CLA) bought the property and remaining buildings. This company’s main business was the manufacture of liquid oxygen for various industrial purposes. At first, the company sold much of its oxygen to the city’s metal fabricating firms to fuel their oxyacetylene welding processes.

In 1946, Stelco and CLA teamed up to perform combustion air enrichment experiments in an open hearth furnace. Using basic oxygen drastically increases steelmaking capacity. In 1954, Dofasco built the first oxygen steelmaking plant in North America and became a major CLA customer.

Now called Air Liquide, the Hamilton plant has become one of the largest oxygen plants in North America. The company uses an elaborate underground pipeline network to supply oxygen to Stelco and Dofasco, as well as other industries and hospitals in the city.

Percy Moule worked as a pipefitter before taking a job at CLA in 1941. He supervised the mechanical process which brought air into the plant through a large intake pipe on the roof, split it up into nitrogen, oxygen and argon, and then channeled it to special containers to await delivery. It was an odd job, he remarked in 1958, because "you’re dealing with transformations and processes you can’t see, and with substances you can’t see."