Oki C3520 - Manual (Page 94)

Maintenance > 94
5. Starting from the rear, lift each of the image drum units,
out of the printer and place them in a safe place away
from direct sources of heat and light.
CAUTION!
The green image drum surface at the base of each
cartridge is very delicate and light sensitive. Do not
touch it and do not expose it to normal room light for
more than 5 minutes. If the drum unit needs to be out
of the printer for longer than this, please wrap the
cartridge inside a black plastic bag to keep it away
from light. Never expose the drum to direct sunlight
or very bright room lighting.