Lenovo IdeaCentre B500 Safety And Warranty Manual page 24

Warning
Must fully remove the dustproof shield (if provided) to facilitate the heating
eradiation and ventilation when the computer is running or before the power
supply of the computer is completely switched off.
6. Keep the computer away from objects or environments with electromagnetic
interference (EMI) such as magnets, working mobile phones and electrical
appliances.
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Safety and warranty guide