Fujitsu fi-4120C Operator's Manual page 16

Do not use aerosol sprays near the scanner.
Do not use aerosol sprays to clean the scanner. Aerosol sprays cause dirt and dust to
enter the scanner, resulting scanner failure and malfunction.
Disconnect the power plug from the power outlet when the
scanner is not used for a long period of time.
When the scanner is not used for a long period of time, be sure to disconnect the
power plug from the power outlet for safety.
Do not install the scanner in the direct sunlight.
Do not install the scanner in the direct sunlight or near heating apparatus. Doing so
might cause excessive heat to build up inside the scanner, causing fire or scanner
trouble. Install the scanner in a well-ventilated location.