The back of the housing has a 70mm x 25mm fan on the back. What makesthe fan unique is that it is a squirrel fan and is set to blow down into the bottom of the case. The sensor selection jumper is on the upper right on the back of the ISWAP, which allows you to choose from 3 different temperatures: 45 C, 55C (Default), and 65C. When the sensor detects a hard drive failure or over heat it will trigger an alarm and a LED to let you know something is wrong.