In summary, reverse rotation is the phenomenon caused by airflow moving backwards through a fan and causing the impeller to spin in the opposite direction. Reverse rotation can happen due to a variety of different operating conditions. Due consideration should be taken to prevent a failure of equipment with multiple fans or hot swapping functionality. Reducing the speed or adding a Louver System are the best ways to prevent reverse rotation in high static hot swapping applications. Reverse rotation at startup can be prevented by starting up all fans simultaneously or start up all fans at reduced speed prior to increasing to full speed. When proper steps have been taken, reverse rotation can be prevented which will reduce system down time.