A Case fan, sometimes called a system fan, is a computer case mounted internal fan designed to bring cool air in and exhaust hot air out of your PC. They come in a variety of sizes, with 120mm, 140mm and 200mm fans being the most popular. They are available with various options for performance and aesthetics, such as LED lighting.

The function of a case fan is to draw air into the computer, where it passes over critical components that generate heat during operation. Cool air is then dissipated, and the Case fans positioned at the back and top of the case help to exhaust the heated air. This creates a continuous flow of cool air in and out, helping to keep the components inside your computer cool and performing at peak performance.

When choosing a case fan, pay attention to its CFM (Cubic Feet Per Minute) rating and noise level, as well as its bearing type. Fan noise is measured in decibels, and the lower the decibel rating, the quieter the fan. Fan size also has an impact on how much air it moves, with larger fans able to spin more slowly while still moving the same amount of air as smaller fans.

Keeping in mind that the goal is to create a continuous stream of cool air passing over the CPU, GPU and other hot components, you should try to position your case fans for the best results. Front, Rear, and Top configuration is ideal, as is having the front intake fan with a rear exhaust to push air upward.