Catalytic converters are emissions control devices installed in a vehicle’s exhaust system, downstream of the exhaust manifold. They utilize catalysts – typically platinum, palladium, and rhodium – to convert harmful hydrocarbons, carbon monoxide, and nitrogen oxides into less toxic substances like water, carbon dioxide, and nitrogen. Construction commonly features a ceramic or metallic honeycomb substrate to maximize surface area for catalytic reaction. Modern units often incorporate oxygen sensors upstream and downstream to monitor converter efficiency and feedback to the engine control unit. Variations exist based on vehicle type and emissions standards, impacting substrate material, catalyst loading, and overall dimensions.