What does emission control system refer to?

• A. Systems designed to reduce harmful emissions from the engine
• B. Systems that cool the engine
• C. Systems that boost horsepower
• D. Systems that manage vehicle speed

Answer: (A)

Emission control systems are the parts of the engine and exhaust that reduce the pollutants released into the air. They treat exhaust so harmful gases are converted or trapped before leaving the tailpipe. For example, catalytic converters transform carbon monoxide and hydrocarbons into less harmful substances, diesel particulate filters trap soot, and exhaust gas recirculation lowers combustion temperatures to reduce NOx formation. Some buses use selective catalytic reduction with a urea solution to further convert NOx into nitrogen and water. These systems exist to meet environmental regulations and are distinct from cooling the engine, boosting horsepower, or managing vehicle speed.