William T. Smith, 79, a retired government engineer who owned and operated his own consulting firm in Silver Spring for nine years before retiring a second time earlier this year, died of cancer Sept. 19 at Washington Adventist Hospital.

Mr Smith joined the government in 1943 as a civilian air-conditioning engineer with the Army in Atlanta. He came to Washington in 1949 and became the Air Force's senior engineer responsible for its refrigeration and air conditioning projects.

He also was a senior engineering consultant to a number of other organizations, including the United Nations and the State Department, on cooling projects.

Upon retiring from the Defense Department in 1970, he was awarded the Department's Distinguished Service Medal.

Mr. Smith was a member of the Toastmasters Club and the Kiwanis Club, both in Silver Spring. He helped found an awards program with the Kiwanis Club for the Silver Spring police.

He was a member of the Society of American Military Engineers, and a life member of the American Society of Heating, Refrigerating and Air Conditioning Engineers.

Survivors include his wife, the former Frances Medders, of the home in Silver Spring; a daughter, Sue Tammen, of Rockville; and a brother, Stone, and a sister, Lucille Smith, both of Mississippi.