For most desktop Baby AT systems, the processor is located near the front, and thus intake vents on the front panel work best. For Baby AT tower systems, vents on the bottom of the front panel work best. For ATX and microATX systems, vents should be located both in the bottom front and bottom rear of the chassis. For most ATX and microATX systems, power supplies that act as an exhaust fan, drawing air out of the system, work most efficiently with active fan heatsinks. For most Baby AT systems, the power supply fan acts as an exhaust fan, venting system air outside the chassis.
Some power supplies have markings noting airflow direction.
Ensure the proper power supply is used based upon the system form factor. Depending upon the type of power supply, the fan either draws air into or out of the chassis. If intake and exhaust vents are properly located, the power supply fan can draw enough air for most systems. For some chassis where the processor is running too warm, changing to a power supply with a stronger fan can greatly improve the airflow. Choose a power supply unit with large vents.