HP ProBook 5220m Notebook PC - Manual (Page 20)

Bottom components
Component Description
(1) Battery release latches (2) Release the battery from the battery bay.
(2) Battery bay Holds the battery and the subscriber identity module (SIM).
(3) Service access door release latches (2). Release the service access door.
(4) Vents (3) Enable airflow to cool internal components.
NOTE: The computer fan starts up automatically to cool internal
components and prevent overheating. It is normal for the internal
fan to cycle on and off during routine operation.
(5) Service access bay Provides access to the hard drive, 2 memory module slots, the
wireless local area network (WLAN) module, and the HP Mobile
Broadband Module (not supported by the Linux operating system).
8 Chapter 1 Features