Cisco 350 Series Administration Manual page 71

5 Status and Statistics
Health and Power
Fans
In some devices the fans are mandatory for the device operation since without them the device
becomes too hot and automatically shut-down. Since a fan is a moving part, it is subject to
failures. A redundant fan is installed on the system. This fan is not operational unless one or
more of the system fans fails. In this case, the redundant fan becomes part of the environment
monitoring of the device.
It is recommended to let the redundant fan work for at least 1 minute once a day.
58 Cisco 350, 350X and 550X Series Managed Switches, Firmware Release 2.4, ver 0.4