Carpet cleaning, for beautification, and the removal of stains, dirt, grit, sand, and allergens can be achieved by several methods, both traditional and modern. Clean carpets are recognized by manufacturers as being more visually pleasing, potentially longer-lasting, and probably healthier than poorly maintained carpets.

Sanitary Maintenance magazine reports that carpet cleaning is widely misunderstood, and chemical developers have only within recent decades created new carpet-care technologies. Particularly, encapsulation and other green technologies work better, are easier to use, require less training, save more time and money, and lead to less resoiling than prior methods.

The professional carpet-cleaning industry is primarily educated and unofficially governed by the Institute of Inspection, Cleaning, and Restoration Certification (IICRC). It is a nonprofit certifying body for the specialized fabric-cleaning industry that sets modern carpet-cleaning standards. It accepts five basic dry and wet professional cleaning methodologies.

Dry-cleaning

Many dry carpet-cleaning systems rely on specialized machines; dry carpet-cleaning machines include those manufactured by Brush and Clean, Host Dry, and Whittaker System. These systems are mostly technically "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, or of pretreatments, preconditioners, or "traffic-lane cleaners", which are detergents or emulsifiers that break the binding of different soils to carpet fibers over a short period of time, commonly sprayed onto carpet prior to the primary use of the dry-cleaning system. One chemical dissolves the greasy films that bind soils and prevent effective soil removal by 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.

Dry compound

A biodegradable absorbent powder and cleaning compound may be spread evenly over carpet and brushed or scrubbed in. For small areas, a household hand brush can work such a compound into carpet pile; dirt and grime is attracted to the compound, which is then vacuumed off, leaving carpet immediately clean and dry. For commercial applications, a specially designed cylindrical counter-rotating brushing system is used, without a vacuum cleaner. Machine scrubbing is more typical, in that hand scrubbing generally cleans only the top third of carpet.

Encapsulation

In the 1990s, new polymers began literally encapsulating (crystallizing) soil particles into dry residues on contact, in a process now regarded by the industry as a growing, up-and-coming technology; working like "tiny sponges", the deep-cleaning compound crystals dissolve and absorb dirt prior to its removal from the carpet. Cleaning solution is applied by rotary machine, brush applicator, or compression sprayer. Dry residue is vacuumable immediately, either separately or from a built-in unit of the cleaning-system machine. According to ICS Cleaning Specialist, evidence suggests encapsulation improves carpet appearance, compared to other systems; and it is favorable in terms of high-traffic needs, operator training, equipment expense, and lack of wet residue. Encapsulation also avoids the drying time of carpet shampoos, making the carpet immediately available for use.

The use of encapsulation to create a crystalline residue that can be immediately vacuumed (as opposed to the dry powder residue of wet-cleaning systems, which generally requires an additional day before vacuuming) has recently become an accepted method for commercial and residential carpet maintenance.

Bonnet

After club soda mixed with cleaning product is deposited onto the surface as mist, a round buffer or "bonnet" scrubs the mixture with rotating motion. This industry machine resembles a floor buffer, with an absorbent spin pad that attracts soil and is rinsed or replaced repeatedly. The bonnet method is not strictly dry-cleaning and involves significant drying time, and usually only addresses the top third of carpet, making it a quick solution rather than a deep cleaning of dirt or odor as considered suitable for valuable carpet. To reduce pile distortion, the absorbent pad should be kept well-lubricated with cleaning solution.

When there is a large amount of foreign material below the carpet backing, extraction with a wet process may be needed. The spin-bonnet method may not be as capable of sanitizing carpet fibers due to the lack of hot water, but a post-cleaning application of an antimicrobial agent is used to make up for this. Compared to steam cleaning, the small amounts of water required with spin-bonnet carpet cleaning favor water-conservation considerations.

Wet-cleaning

Wet-cleaning systems naturally require drying time, which has led to customer fears and concerns about very slow drying, the risk of discoloration returning during drying, and odors, bacteria, fungi, molds, and mildews. Balancing the need for 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) is a key technique that must be mastered by carpet-cleaning technicians.

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 resoiling.

Steam cleaning

In high-pressure hot water extraction ("steam cleaning"), after preconditioning with an alkaline agent, agitation with a grooming brush, and appropriate dwell time, a pressurized manual or automatic cleaning tool (such as a wand) passes over the surface several times to thoroughly rinse out all preconditioner, residue, and particulates, and, using an acetic acid solution, to restore neutral fiber pH. The acid rinse thus neutralizes the alkaline residues, and can contribute to softening cleaned fabrics.

Rather than soaps, the steam-cleaning system uses detergent-based solutions that dry to a powder or crystal. The surface is dried to avoid saturation, typically taking 3–4 hours if done correctly; inexperienced carpet-cleaning companies sometimes overwet carpeting, leading to mold and recurring stains (arising from the "wicking" effect, whereby deeper soils are water-driven upward along carpet fibers, thus reconstituting visible stains). Some carpet-cleaning solutions are carbonated to dissolve organic material more effectively. Beyond these treatments, antistaining and antisoiling products can be applied by the carpet owner, and have for this reason become recognized in the carpet-cleaning industry as some of its biggest profit centers.

Extraction is by far the most important step in this process. Since the hot-water extraction method uses much more water than other methods like bonnet or shampoo cleaning, proper extraction is critical to avoid oversaturation. When carpet is saturated, there is a risk that soils and residue from deep in the carpet fiber and backing will "wick" up to the surface, resulting in browning, or the carpet layers may delaminate.

Hot-water extraction generally involves slower drying times, lower production rates, and more labor-intensive processes than dry carpet cleaning. 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.

Shampoo

Wet shampoo cleaning with rotary machines, followed by thorough wet vacuuming, was widespread until about the 1970s, but industry perception of shampoo cleaning changed with the advent of encapsulation. 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.

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.

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

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. Models include upright (dirty-air and clean-air), canister and backpack, wet-dry and pneumatic, and other varieties. Robotic vacuum cleaners have recently become viable as well.

Vacuum-cleaner manufacturers are widespread and include Aerus LLC, Bissell Carpet Sweepers, Black & Decker DustBuster, Dirt Devil, Dyson, Electrolux, Eureka, Goblin Vacuum Cleaners, the Hoover Company, the Kirby Company, Nilfisk-Advance, Numatic International Limited, the Oreck Corporation, Regina Vacuum Cleaners, Rexair LLC, Samsung Electronics, Sebo Vacuum Cleaners, Tacony Corporation, Vax Vacuum Cleaner Ranges, Vorwerk, and Wertheim Vacuum Cleaners.

Stain removal

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. 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. 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 (Kool-Aid, Gatorade, Listerine, soda, etc.). These may be removed by professionals 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.

Misconceptions

Robert Wittkamp (1942–2007), IICRC-certified master cleaning 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.