Many factors figure into this decision. Among those are obvious things such as the amount of foot traffic, the frequency of vacuuming, the number of kids in the home, and the number and types of indoor pets. Other, less noticeable, factors include internal and external pollution levels, the age of the carpet and, possibly, existing manufacturer warranties. Most manufacturers require that in order to maintain the warranty the carpet should be professionally cleaned every 18 to 24 months. As a general rule, however, most residential carpets should be cleaned at least once per year. Carpets in commercial buildings should be done at least two or three times annually. Remember, if you think your carpets might be dirty – they probably are.