Dr. Robert Pfanstiel, 94, a retired research chemist who had worked for the government on chemical warfare after World War I and on development of the atomic bomb during World War II, died of a respiratory ailment Saturday at the Leewood Nursing Home in Annandale, where he had lived for about three years.

A former resident f Lakewood, Ohio, Dr. Pfanstiel moved to Springfield in 1972 to live with his daughter, Irene A. Bowman.

Dr. Pfanstiel was a research chemist for the Graselli Chemical Division of the E.I DuPont de Nemours Co. in Cleveland from about 1928 until his retirement in 1950.

From 1922 to 1925, he worked for the Army's Chemical Warfare Service at Edgewood (Md.) Arsenal, where he was in charge of research on chemical agents to counteract the effects of mustard gas, which was widely used in World War I. He held a number of patents in this field. w

During World War II, Dr. Pfanstiel was one of three scientists selected to calculate the explosive power of both the atom and hydrogen bombs as part of this country's Manhattan Project, which led to development of the atomic bomb. He was cited by President Franklin D. Roosevelt for his work on the project.

Dr. Pfanstiel was born in Morning View, Ky. He earned a bachelor's degree and a master's degree in industrial chemistry from the University of Kentucky and a doctorate in physical chemistry from the University of Pennsylvania in 1922. He was a 50-year member of the American Chemical Society.

His marriage to the late Luella S. Pennington ended in divorce.

Besides his daughter, survivors include two grandchildren and one great-grandson.