What pollutant are catalytic converters primarily used to reduce in vehicle exhaust?

• A. They reduce nitrogen oxides in vehicle exhaust.
• B. They increase sulfur emissions.
• C. They generate nitrogen oxides.
• D. They remove oxygen from the air.

Answer: (A)

Catalytic converters clean exhaust by using a surface that speeds up reactions to turn harmful gases into less harmful ones. The pollutant they primarily target is nitrogen oxides, formed at high engine temperatures when nitrogen from the air reacts with oxygen. Inside the converter, NOx is reduced on the catalyst to nitrogen gas and oxygen, while carbon monoxide and unburnt hydrocarbons are oxidized to carbon dioxide and water. This is why nitrogen oxides are the main pollutant addressed. They do not increase sulfur emissions, they do not generate NOx, and they don’t remove oxygen from the air.