Although there is an industrial cleaning process that is in fact steam cleaning, in the context of carpet cleaning, “steam cleaning” is usually a misnomer for or mis-characterization of the hot water extraction cleaning method. The hot water extraction cleaning method uses equipment that sprays heated water (not steam), sometimes with added cleaning chemicals, on the carpet while simultaneously vacuuming the sprayed water along with any dislodged and dissolved dirt. Many carpet manufacturers recommend professional hot water extraction as the most effective carpet cleaning method. Actual steam could damage man-made carpet fibers or shrink natural fibers such as wool.
The primary advantage of the hot water extraction cleaning method is that effective cleaning is possible using only hot water, or hot water with very diluted detergent solutions. This avoids the problems associated with detergent residues that can remain in the carpet with other cleaning methods. Detergent residues on carpet fibers can attract dirt from the soles of shoes as people walk on a carpet, causing the carpet to become dirty again soon after cleaning.
However, in many cases there IS excessive chemical residue left in the carpets, either from the operator not following the recommended manufacturers’ dilution ratios for the cleaning solution products they are using, or just from simply thinking that “more cleaning chemicals will get it cleaner” while they are in the middle of actually doing the room-to-room “steam” cleaning hot water extraction process. Checking for excessive residue can be a simple as touching the carpet fibers in a section that has just been cleaned and rubbing the fingers and thumb together, feeling and smelling for a sensation of ‘slickness’ and a detergent odor on the fingertips.
The primary disadvantage of the hot water extraction cleaning method is that 100% of the water used cannot be removed. If poor water extraction is achieved, in conditions of high humidity, mold growth could occur or be exacerbated. This is not usually a problem with high end commercial water extraction equipment. Moisture left in carpets after cleaning will evaporate more quickly with ventilation, heating, air conditioning or dehumidification.