Which component is not part of the environmental control system?

The fuel pump is not part of the environmental control system because its primary function is to supply fuel to the aircraft's engines, rather than to regulate the cabin environment. The environmental control system is designed to manage various factors within the aircraft’s cabin, such as temperature, humidity, and air quality. This system includes components like the air conditioning unit, which cools the air; the heating system, which warms the air; and the ventilation system, which circulates and replenishes cabin air. Each of these elements works together to ensure passenger comfort and safety by maintaining a suitable atmosphere within the aircraft. In contrast, the fuel pump is crucial for engine operation, not for maintaining the environmental conditions in the cabin.