Computer cooling is required to remove the waste heat produced by contamination of dust or computer components, to keep them within their safe operating temperature (otherwise it could cause an explosion) limits. Mostly, Computer Exhaust Fan are used for this purpose (Case or wall mounts, Graphics card fan, CPU Exhaust fan, etc.). These fans are manufactured by Panasonic, Sharkoon, Thermaltake, Ebm-papst, Nexus, Nidec, Noctua and NorthQ. Usually, these fans are sound proof, but sometimes they produce undesired noises. Like all other things, there exists varied cooling methods for computers.Many computers, such as simple home computers and business (industrial) computers, can rely on passive cooling alone, and usually do not require a case fan to keep a computer in case at ordinary operating temperature. Under clocking and/or undervolting reduces high power dissipation. Larger heat sinks are more unusual solutions and examples of which are water cooling, heat pipes bonded to the metal case, or refrigeration. Motherboards dipped in liquid oil provides excellent convection cooling and protects components from humidity and water without the need for fans or heat sinks. Blowers can also be used to remove the dust from components, which is by far, biggest source of heat. Ionic wind cooling is being researched, where air is moved by ionizing air between two electrodes. It replaces the fan and has the advantage of no moving parts.