These waters are produced as a result of some sort of heat exchanger where heat is removed from the product. Waters can be used once or recycled. Recycling creates the necessity for periodic cleaning, where at least some may be released into the environment. This is the least dangerous the waste waters, but because of leaks within the process, could contaminate the surroundings. This type of waste must also be monitored and often treated, and is also a major factor in thermal pollution of water sources.