What is the primary purpose of an exhaust emission system?

The primary purpose of an exhaust emission system is to reduce air pollution. These systems are designed to filter and treat the gases produced during the combustion process in a vehicle's engine before they are released into the atmosphere. By containing various components such as catalytic converters, mufflers, and exhaust gas recirculation (EGR) systems, the exhaust emission system reduces harmful emissions, including carbon monoxide, hydrocarbons, and nitrogen oxides. This reduction is crucial for protecting air quality and public health, as vehicle emissions can contribute significantly to environmental pollution and respiratory issues.

While options like improving fuel efficiency and enhancing engine performance may seem beneficial, they are secondary outcomes related to the proper functioning of the exhaust emission system rather than its primary goal. Creating noise for safety is not relevant to the object's intended use in pollution control.