Passive cards do not include a built-in fan and therefore require an external mechanism to ensure proper airflow for cooling. Passive cards should not be powered without a forced airflow mechanism in place. The passively cooled Alveo U280 cards support airflow as illustrated below.
Figure 1. Airflow Direction for Passively Cooled Cards
Note: Other environmental conditions are possible, including bidirectional flow. However, this is specific to server configurations, and testing is performed by individual OEMs. Contact your server provider for more information and options.