Carl Keith, a co-inventor of the three-way automotive catalytic converter — a major advance in eliminating the toxic tailpipe emissions that once blanketed cities in smog — died Nov. 9 while visiting one of his daughters in New Bern, N.C. He was 88 and lived on Marco Island in Florida.

His grandson Leonard Hardesty Jr. confirmed the death.

Working with John Mooney and a team of other chemical engineers at the Engelhard Corp., one of the world’s largest mineral-refining companies, Keith designed the three-way catalytic converter in the early 1970s, just as the stricter emission requirements of the Clean Air Act Extension of 1970 were coming into effect.

“Billions of people around the world breathe cleaner air because of this invention,” Margo Oge, director of the Office of Transportation and Air Quality at the Environmental Protection Agency, said Friday.

The three-way converter was a significant improvement over what is called the oxidizing converter, the patent for which is held by General Motors. The three-way is now standard for cars and light trucks made in the United States and in most of the rest of the world.

Lindsay Brooke, a senior editor of Automotive Engineering International, the magazine of the Society of Automotive Engineers, said Thursday in an interview, “The catalytic converter, combined with the transition to unleaded gasoline, led to a dramatic improvement in air quality and enabled the auto industry to meet the Clean Air Act regulations.”

A catalytic converter is a can-shaped device installed beneath a vehicle as part of the exhaust pipe. Inside the converter, a bricklike ceramic honeycomb with hundreds of tiny passages is coated with a catalyst material, typically platinum or palladium. When the exhaust flows out of the engine and passes over and through the catalyst coating, a chemical reaction renders three toxic compounds harmless.

The oxidizing converter worked for two of those compounds, turning carbon monoxide into carbon dioxide and hydrocarbons into carbon dioxide and water. The three-way device designed by Keith and his colleagues added the conversion of nitrogen oxides into nitrogen and water.

In 2002, President Bush presented Keith and Mooney with the National Medal of Technology, the nation’s highest honor for technological innovation.