Most 5520 Series switches are available with front-to-back airflow. In this switch, the fan modules are labeled Air Out.
Models 5520-24T-BASE, 5520-24T-ACDC, 5520-24X-BASE, 5520-24X-ACDC, 5520-48T-BASE, 5520-48T-ACDC, 5520-48SE-BASE, and 5520-48SE-ACDC are available with back-to-front airflow or front-to-back airflow. In switches with back-to-front airflow, the fan modules are labeled Air In.
All installed fan modules must blow air in the same direction and must match the airflow direction of the installed power supplies.
The latch on the power supply is color-coded to indicate airflow direction. PSU modules with a red latch have front-to-back airflow. PSU modules with a blue latch have back-to-front airflow.