Air filters are designed to maintain proper airflow within the Controller by keeping the air circulating inside the chassis clear and free of dust.
Each Controller has an air filter covering the front of the chassis. Air filters are customer replaceable units (CRUs). Replacing the air filter does not require you to bring the Controller offline. The following figure shows the Controller air filter.
Tip: Wait two minutes before re-seating the air filter to allow the energy storage modules (ESMs) to drain. Otherwise, potential damage might occur if the ESMs are not completely discharged.
Figure 1 Controller air filter 
Procedure Overview