Fans
Cooling Fans
The Acme Packet 3900 chassis pulls cool ambient air into the chassis through two front-installed intake fans and exhausts heated air through perforated air outlets located along the rear of the chassis. To avoid overheating the system, do not block the air intake or exhaust or otherwise obstruct airflow to the unit in any way.
Each individual fan attaches to the chassis with two captive screws, and is powered by a connector that joins the fan to the motherboard when screwed into the chassis.

Intake Fans
The intake fans are hot-pluggable and are covered by an air filter that prevents excess dust and contaminants from entering the system. The air filter is retained by the removable front bezel.
The Acme Packet 3900 automatically adjusts the fan speed based on the current operational status and environmental conditions. Fan speed regulation is an automated process that requires no user intervention. You can monitor the status of the fan speed from the Environment menu.
Each fan is a user-replaceable, hot-swappable component. If the Acme Packet 3900 experiences a fan malfunction and generates an alarm, you must remove the existing fan and replace it with a fully functioning fan.