A common process of hot water extraction  begins with preconditioning. Alkaline agents such as ammonia solution for synthetic carpets, or acidic solution (such as vinegar solution) for woolen carpets, are sprayed into the carpet, then agitated with a grooming brush or an automatic scrubbing machine. Next, a pressurized manual or automatic cleaning tool (such as a wand) passes over the surface to rinse out all pre-conditioner, residue, and particulates. If an alkaline detergent is used on a woolen fibre, use of an acetic acid solution will restore neutral fiber pH. The acid rinse thus neutralizes the alkaline residues, and can contribute to softening cleaned fabrics. The hot water extraction method is the preferred method of many carpet manufacturers. Extraction is, by far, the most important step in the hot water extraction process. Since the hot-water extraction method uses much more water than other methods like bonnet or shampoo cleaning, proper extraction and air flow are critical to avoid drying issues. Drying time may also be decreased by extra use of fans, air conditioning, and/or outdoor ventilation. Older surfaces, such as double jute-backed carpets and loose rugs with natural foundation yarns, could shrink after a wet treatment, leading to suppositions that wet-cleaning could also remove wrinkles. However, this notion is antiquated and this method could also occasionally tear seams or uproot strips. Newer carpets, such as with synthetic backing and foundation yarns, do not shrink, and they smooth easily; in such carpets, wrinkles indicate an underlying problem, such as adhesive, that may need a certified carpet inspector to determine. Wet-cleaning systems naturally require drying time, which may lead to concerns about very slow drying, the risk of discoloration returning during drying, and odors, bacteria, fungi, molds, and mildews. Carpet cleaning specialists try to find a balance between rapid drying (attributable to lower flow rate through the cleaning jets of a spray system) and the need to remove the most soil (attributable to higher flow rate). Pretreatments similar to those in dry-cleaning and "very low moisture" systems are employed, but require a longer dwell time of 15 to 20 minutes, because of lower amounts of carpet agitation. Ideal pretreatments should rinse easily and leave dry, powdery, or crystalline residue that can be flushed without contributing to re-soiling. Dry-cleaning For more details on this topic, see Dry carpet cleaning. Many dry carpet-cleaning systems rely on specialized machines. These systems are mostly "very low moisture" (VLM) systems, relying on dry compounds complemented by application cleaning solutions, and are growing significantly in market share due in part to their very rapid drying time, a significant factor for 24-hour commercial installations. Dry-cleaning and "very low moisture" systems are also often faster and less labor-intensive than wet-extraction systems. Heavily soiled areas require the application of manual spotting, pretreatments, preconditioners, and/or "traffic-lane cleaners", (commonly sprayed onto carpet prior to the primary use of the dry-cleaning system) which are detergents or emulsifiers which break the binding of different soils to carpet fibers over a short period of time. For example, one chemical may dissolve the greasy films that bind soils to the carpet, and thus prevent effective soil removal through vacuuming. The solution may add a solvent like d-limonene, petroleum byproducts, glycol ethers, or butyl agents. The amount of time the pretreatment dwells in the carpet should be less than 15 minutes, due to the thorough carpet brushing common to these "very low moisture" systems, which provides added agitation to ensure the pretreatment works fully through the carpet. The benefit of dry carpet cleaning, over wet solutions, is that dry chemical compounds don't attract dirt, like dried shampoo. While dry carpet cleaning is more expensive and more time consuming to clean than Bonnet or extraction, dry cleaning formulas put less stress on the carpets themselves. Dry compound This section does not cite any sources. Please help improve this section by adding citations to reliable sources.
Hot-water extraction, also regarded as preferable, had not been introduced either. Wet shampoos were once formulated from coconut oil soaps; wet shampoo residues can be foamy or sticky, and steam cleaning often reveals dirt unextracted by shampoos. Since no rinse is performed, the powerful residue can continue to collect dirt after cleaning, leading to the misconception that carpet cleaning can lead to the carpet getting "dirtier faster" after the cleaning. The best method is to combine shampoo and extraction, first shampoo with a spin brush to loosen the dirt and the pile, then extraction the carpet. But this needs time and double rinsed is necessary and the drying time is up to 24 h. When wet-shampoo chemistry standards converted from coconut oil soaps to synthetic detergents as a base, the shampoos dried to a powder, and loosened dirt would attach to the powder components, requiring vacuuming by the consumer the day after cleaning. Dry foam carpet cleaning This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (March 2015) (Learn how and when to remove this template message) Dry foam cleaning involves applying cleaning foam and immediately vacuuming the foam. It is not a completely dry method since the foam is 90% air and 10% liquid. A dry foam machine consists of a pressure tank in which a solution of water and shampoo is added. This method is used for water sensitive carpets, needle felt, and other carpet types whose construction inhibits sufficient water extraction. Vacuum wash This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (March 2015) (Learn how and when to remove this template message) Vacuum washing employs a washhead that sprays water without detergent and immediately removes it by suction, creating a swirl of water. This ensures high cleaning performance, extracting the dirt from the carpet to a depth of half inch. By immediately reabsorbing the wash water, the drying time greatly shortened. This method is suitable for intermediate and basic cleaning. Because it does not require cleaning products, it leaves no detergent residue. Vacuum washing has long been in use in Europe, mostly in larger train and bus companies, schools, and historic preservation. The system works on all surfaces which are water resistant (carpet, upholstered furniture, wooden floors, stone, plastics). A great advantage is that this system works without brushes or pads so there is no abrasion on pile. Household processes
Other household carpet-cleaning processes are much older than industry standardization, and have varying degrees of effectiveness as supplements to the more thorough cleaning methods accepted in the industry. Vacuum For more details on this topic, see Vacuum cleaner. Vacuum cleaners use air pumps to create partial vacuums to suck up dust and dirt, usually from floors and carpets. Filtering systems or cyclones collect dirt for later disposal. Modern carpet cleaning equipment use rotary vacuum heads and spray jets to deep clean the carpet through hundreds of multi-directional cleaning passes. Some add steam and agitation. Models include upright (dirty-air and clean-air), canister and backpack, wet-dry and pneumatic, and other varieties. Robotic vacuum cleaners have recently become available. Stain removal Cleaned and uncleaned areas of a carpet Tea leaves and cut grass were formerly common for floor cleaning, to collect dust from carpets, albeit with risks of stains. Ink was removed with lemon or with oxalic acid and hartshorn; oil with white bread or with pipe clay; grease fats with turpentine; ox gall and naphtha were also general cleaners. Ammonia and chloroform were recommended for acid discoloration. Benzine and alum were suggested for removing insects; diatomaceous earth and material similar to cat litter are still common for removing infestations. Candle wax is removed by placing a towel over the affected carpet area and applying steam from a clothes iron until the wax absorbs into the towel. Some traditional methods of stain removal remain successful and ecological. Caution should be addressed when treating natural fibers such as wool. The longer the stain material remains in the carpet, the higher the chance of permanent color change, even if all the original stain material is removed. At times pets urinate on the carpet and this results in a bad odor especially when it is hot and humid.The carpet or rug is usually taken outside and immersed in water to remove such stains. Immediately blotting (not rubbing) the stain material as soon as possible will help reduce the chances of permanent color change. Artificial food coloring stains are generally considered permanent stains. These may be removed by professional cleaners or deep cleaning rental machines with heat-transfer stain-reducing chemicals, but carry risks of burning the carpet. Stain removal products can be combined with anti-allergen treatments to kill house dust mites. Other Carpet rods, rattan rugbeaters, and carpet-beating machines for beating out dust, and also brooms, brushes, dustpans, and shaking and hanging were all carpet-cleaning methods of the 19th century; brooms particularly carry risks of wear. Steam cleaning increases the lifespan of your carpet. Misconceptions Robert Wittkamp (1942–2007), IICRC-certified master Carpet Cleaners technician with 30 years' expertise in carpet cleaning, commented that old wives' tales persist and thrive within the industry. For instance, the concept that walking barefoot on a carpet may lead to damage from body oils has not been supported or disproven by standardized reports or testing or by industry evidence.