Which component of the CRJ 700 interacts directly with the cabin atmosphere during flight?

The environmental control system is responsible for managing and regulating the cabin atmosphere during flight, including aspects such as air temperature, pressure, humidity, and airflow. This system ensures that passengers and crew have a comfortable and safe environment while in the aircraft. It interacts directly with the cabin atmosphere by bringing in fresh air, recycling cabin air, and controlling temperature through heating or cooling methods.

In contrast, the oxygen system is designed primarily for providing supplemental oxygen in emergency situations, and while it is related to cabin safety, it does not continuously interact with the cabin atmosphere under normal operations. The potable water system is focused on providing safe drinking water and does not play a role in managing the cabin atmosphere. The fire suppression system is critical for safety in case of fire but does not have any interaction with the cabin's overall atmosphere during flight. Thus, the environmental control system is the only component among the options that directly interacts with and manages the conditions of the cabin atmosphere.