Huawei EchoLife HG520 User Manual page 6

In a lightning storm, turn off the equipment and unplug the power
supply, to avoid lightning strike.
Unplug the power supply if the equipment is not used for a long
time.
In case of exceptions, turn off the equipment and unplug the
power supply immediately. Then contact your supplier for
maintenance. For example, the equipment emits smoke, peculiar
smell or exceptional sounds.
Cleaning
Before cleaning the equipment, turn off the equipment and unplug
the power supply.
Clean the equipment shell with a piece of soft cloth.
It is forbidden to spray liquid onto the equipment, to avoid damage
to the internal circuit.
Keep the power socket clean and dry, to avoid electric shock or
other dangers.
Note
If the device is in use for a long time, temperature of the shell will
go up. Please do not worry. This is normal and the device can
work normally.
Huawei Technologies Proprietary