Hermann Rahn was born in East Lansing, Michigan in 1912, though he spent most of his primary years in Kiel, Germany. His father Otto, a professor of bacteriology, fostered in Rahn a scientific interest in the world around him and Rahn become a keen naturalist. In 1929, Rahn graduated from high school in Ithaca, New York. He earned his bachelor's degree in zoology from Cornell University in 1933 and a PhD from the University of Rochester in 1938.

After a fellowship at Harvard University, Rahn worked as an instructor in physiology at the University of Wyoming, Laramie. In 1941, he returned to the University of Rochester to teach physiology. Although Rahn's training was in zoology, World War II caused him to shift focus to human respiration. It was during his tenure at Rochester that Rahn partnered with friend and mentor Wallace O. Fenn to publish A Graphical Analysis of the Respiratory Gas Exchange in 1955. This paper included the landmark O2-CO2 diagram, which formed the basis for much of Rahn's future work. Rahn's research into applications of this diagram lead to the development of aerospace medicine and advancements in hyperbaric breathing and high-altitude respiration.

In 1956, Rahn joined the University at Buffalo (UB) as the Lawrence D. Bell Professor and Chairman of the Department of Physiology. During his early years as Chairman, Rahn built a strong faculty that could grow the department. With this faculty's support he garnered several grants on the effects of altitude, diving, temperature, and gravity on human performance. Due to his efforts and leadership, the Department become an internationally known research center.

While at UB, Rahn's research interests included ama (the diving women of Korea and Japan who are able to deep-dive without machine assistance) and the gas exchange of avian eggs. In 1973, Rahn was named State University of New York Distinguished Professor of Physiology and stepped down from the chairmanship to pursue more research. Although he spent much time in the lab, Rahn was a dedicated teacher who deeply cared about his students.

Throughout his career, Rahn published frequently and edited several publications, including the American Journal of Physiology and the Journal of Applied Physiology. He served as president of the American Physiological Society and vice president of the International Union of Physiological Sciences. Rahn was a member of the National Academy of Sciences and it's Institute of Medicine.

Rahn was a regular presenter at symposia and conferences and guest lectured often. He was a visiting professor at San Marcos University, Dartmouth Medical School, Laboratoire de Physiologie Respiratoire, and the Max-Planck Institut fur experimentalle Medizin. Rahn was awarded honorary degrees from the University of Paris, University of Yonsei, University of Rochester, University of Lima, and the University of Bern.

Rahn's wife Katherine F. was a landscape architect who was distinguished in her field as well. Together they had two children: Robert F. and Katharine B.

Hermann Rahn died of pancreatic cancer on 23 June 1990. He worked in the laboratory until his cancer prevented it. Always the committed scientist, Rahn was working on a manuscript in bed until the end.

Please see Hermann Rahn's biographical file for more detailed biographies.