From “Experiments on the metabolism of matter and energy in the human body, 1900-1902”.  US Department of Agriculture, Office of Experiment Stations – Bulletin No. 136, by W.O. Atwater and F.G. Benedict, frontispiece.

The respiration chamber was an open-circuit design. Carefully conditioned room air was drawn into the chamber and then evacuated through soda-lime canisters.  The chamber was carefully insulated and kept at a constant temperature by circulating water.