The 1976 Volvo 240 was the first production automobile fitted with a three-way catalytic converter.
Volvo developed the emissions system with California requirements in mind and introduced it on selected 240 models. A three-way catalytic converter reduces three major pollutants: carbon monoxide, hydrocarbons, and nitrogen oxides.
The system depended on a feedback-controlled fuel mixture and an oxygen sensor so the engine could operate near the chemically correct air-fuel ratio. That allowed the catalyst to treat exhaust gases efficiently rather than merely reducing one pollutant.
The Volvo 240 is sometimes confused with earlier catalytic-converter applications, including oxidation catalysts that mainly targeted hydrocarbons and carbon monoxide. The three-way design was a more complete emissions-control milestone and became standard across much of the industry.