HP EliteBook 840 G1 Notebook PC - Manual (Page 23)

Component Description
(2) Service door release lock Releases the service door from the computer.
A security screw is available to prevent the
service door from being accidentally removed.
(3) Vents (2) 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.
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