What is a catalytic converter?

A catalytic converter is a device in a vehicle's exhaust system that chemically converts harmful exhaust gases into less harmful substances before they exit the tailpipe.

Vehicle engines produce three particularly harmful gases:

• Carbon monoxide (CO) — poisonous
• Nitrogen oxides (NOx) — contribute to smog and acid rain
• Hydrocarbons (HC) — unburnt fuel vapours, contribute to smog

Inside the converter is a ceramic or metallic honeycomb structure coated with platinum, palladium, and rhodium precious metals that act as catalysts, speeding up chemical reactions without being consumed.

Two reactions occur:

• Oxidation: CO and HC → CO₂ and water
• Reduction: NOx → harmless nitrogen and oxygen