An independent research team found in 1972 that the “steam extraction method” using hot water was superior to all other types of carpet cleaning. In fact, in 1988 DuPont required that this method be used for their Stainmaster carpets. Read more here.
Be careful with retail steam cleaners and your carpet. Too much heat is not good, and some retail steamer products can damage or destroy your carpet. Professional steam cleaners do not use steam to clean your carpet, despite the name. Instead, they use hot water extraction. Read more about tips and info on cleaning your carpet.