Dell B3465dnf Mono Laser Multifunction Printer - Manual (Page 210)

Cleaning the scanner glass
Clean the scanner glass if you encounter print quality problems, such as streaks on copied or scanned images.
1 Slightly dampen a soft, lint-free cloth or paper towel with water.
2 Open the scanner cover.
3 Clean all the areas shown, and then let them dry.
1
2 3
4
1 White underside of the scanner cover
2 Scanner glass
3 ADF glass
4 White underside of the ADF cover
4 Close the scanner cover.
Maintaining the printer 210