People who have carpets and live in areas that are very humid will have to have a carpet cleaning done by carpet professionals more often than those who live in dry areas. A dirty carpet in a humid area has a much higher risk of developing a mold growth. This is especially true when exposed to moisture.
A professional carpet cleaning company will use a high-powered tool to dry the carpet and reduce moisture. Many homeowners who decide to clean their own carpets do not have this type of equipment and try to dry their carpets by turning on a fan.