Which indicators may suggest a malfunctioning Cabin Atmosphere Control System (CACS)?

Unusual cabin temperature or noise are key indicators that may suggest a malfunctioning Cabin Atmosphere Control System (CACS). The CACS is responsible for maintaining proper temperature, humidity, and air quality within the cabin environment. If the system is not functioning correctly, it can lead to discomfort for passengers and crew, which typically presents as unusual temperature changes—either too hot or too cold—or unexpected noise levels from equipment that is malfunctioning or working harder than normal to compensate for a fault.

By closely monitoring these parameters, crew members can assess the system's functionality and determine if immediate action is necessary to ensure passenger safety and comfort.