General view of the blowing out process for the experimental blast furnace at a Fixed Nitrogen Research Laboratory facility. The process of blowing out, also known as "raking out," is undertaken when production from a blast furnace is no longer required and serves as a means of shutting the furnace down.

The Fixed Nitrogen Research Laboratory (F.N.R.L.) was established at American University in 1919 under the directorship of Arthur B. Lamb. Initially part of the War Department, the F.N.R.L. was the successor to several wartime initiatives to develop a secure domestic supply of nitrate compounds necessary for the manufacture of explosives during World War I. With a staff of about 110 individuals, including 35 to 50 chemists, the F.N.R.L. focused on the manufacture, production, and development of products of atmospheric nitrogen, including munitions and fertilizers.