Dell Precision T3400 (Late 2007) - Manual (Page 23)

Quick Reference Guide 23
• Leave 10.2 cm (4 in) minimum clearance on all vented sides of the
computer to permit the airflow required for proper ventilation.
• If your computer is installed in a corner on or under a desk, leave 5.1 cm
(2 in) minimum clearance from the back of the computer to the wall to
permit the airflow required for proper ventilation.
• If your enclosure has doors, ensure that they allow at least thirty percent
airflow through the enclosure (front and back).