HP Officejet 300 All-in-One Printer - Manual (Page 110)

Maintaining Your HP OfficeJet
Use these guidelines to keep your HP OfficeJet in the best possible
operating condition:
:
Print cartridges dry out and may become unusable when exposed
to air, so:
a) Keep the print cartridge in the print cartridge cradle at all
times.
b) Keep new print cartridges in their sealed packages at room
temperature until you are ready to use them.
c) Do not turn off the HP OfficeJet before printing is complete.
:
Use a soft cloth moistened with water to wipe dust, smudges, and
stains off of the HP OfficeJet's exterior case.
:
The inside of the HP OfficeJet does not require cleaning. Keep
fluids away from the interior of the HP OfficeJet.