Most cleaning professionals and facility managers are aware of the four "fundamentals" of cleaning: agitation, chemicals, time, and heat. But they may not know why is heat so important when it comes to effective cleaning.
To help answer this question, carpet care experts at  U.S. Products, a manufacturer of hot-water carpet extractors, answer the following "heated" questions:
Q: OK, why is heat so critical to cleaning?
A: Heat increases reaction rates, also known as kinetics or the scientific study of motion. When it comes to cleaning, this means that heat increases the reaction the molecular activity of most cleaning chemicals, helping to dissolve, melt, and loosen soils and generally to increase effectiveness
Q: So when it comes to cleaning, is the hotter the better?
A:  As a general rule yes. And in carpet cleaning specifically, you want to maximize the heating performance of your truckmount or portable extractor. There are a few cases where you may want to turn down your heat.
Q: Is using hot water always preferable for carpet cleaning?
A: In most cases, again the answer is yes. There are certain spots on a carpet, such as blood spots, where using too hot of water can make the stain more difficult to remove.  And, as a general rule, we recommend turning down the temperature to a maximum of 160 F for wool carpets.
Q: Is using hot water for carpet cleaning good for the environment?
A: It definitely can be. Because cleaning chemicals clean more effectively due to heat, cleaning professionals may be able to use less of these products, reducing cleaning's impact on the environment overall. According to author Dr. Michael Barry, "Even without soap, small amounts of grease will dissolve in water, [but] the amount increases sometimes ten-fold in hot water."