Carpet Cleaning Methods

November 5, 2002
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The Institute of Inspection, Cleaning and Restoration Certification states that the objective of carpet cleaning is soil removal, that it can be achieved using any of a variety of cleaning methods and, before a method is selected, a number of factors, including carpet type, use, condition and soiling, must first be assessed.

Once that assessment has been made, a method is selected. But what are the options? The IICRC describes five primary methods of cleaning that encompass the majority of professional cleaning occurring today.

This is an abridged look at the methods themselves, not the start-to-finish procedures that are ultimately responsible for successful cleaning. Vacuuming, soil suspension, pre-conditioning, grooming and other procedures are integral parts of the cleaning process; be sure to follow manufacturer recommendations and adhere to the detailed guidelines laid out in the IICRC’s S100 Standard and Reference Guide for Carpet Cleaning Professionals.

Absorbent Compound Method
The absorbent compound method is a minimum-moisture system that uses a granular carrier. Once it is uniformly distributed and dried, the carrier with the absorbed soil is vacuumed from the carpet.

In normal soiling situations, the chemical action is accomplished by using an absorbent compound consisting of cellulose- or polymer-based carrier. The compound is mixed with an anionic or nonionic detergent with a pH range of 5 to 10. Application rates and dispersion methods must follow the manufacturer’s recommendations.

The temperature of the absorbent compound will approximate that of the ambient air in the room being cleaned. Uniform distribution of the compound is generally accomplished using equipment incorporating two counter-rotating brushes, rotary-brush action or hand pile-brushing action.

The compound remains in the carpet until dry, at which time it is extracted with thorough dry vacuuming, preferably with a machine incorporating high-efficiency filtering systems to prevent redistribution of the soils into the air.

Anticipated dry time: 30 to 60 minutes, depending on the use of a pre-conditioner and the quantity of absorbent compound applied.

Dry Foam Cleaning Method
Dry foam cleaning is a minimum-moisture method. Following vacuuming, a dense foam is produced and distributed via a mechanical brush. The excess foam and suspended soil is extracted using a wet vacuum typically incorporated into the same machine.

A properly diluted and aerated (follow the manufacturer’s label directions) dry foam cleaning agent is used. The solution is aerated with mechanical agitation into a dense foam. Agitation may be achieved during or immediately after the application of the dry foam. This is usually accomplished by rotary or cylindrical (reel-type) brushes.

Once the appropriate dwell time has been observed, a wet vacuum attached to or separate from the application machine is used to extract excess foam and the suspended soil. Additional dry vacuuming procedures may also be used after the carpet has dried to extract crystallized detergent residue along with attached soils. High-efficiency filtering systems should be used.

Anticipated dry time: one to three hours, not including heavily soiled areas.

Bonnet Cleaning Method
The bonnet cleaning method is also referred to as the absorbent pad method. It is a minimum-moisture method in which, following vacuuming, a detergent solution is applied to the carpet, then extracted using a bonnet/absorbent pad attached to a drive block on a low-rpm rotary floor machine.

In normal soiling situations, cleaning products used in bonnet cleaning consist of anionic or nonionic detergents and solvents for suspending soils. A carbonated or non-carbonated water-based carrier with a resulting pH of 10 or less may also be used.
Cationic cleaners are not recommended unless specified.

Cleaning agent distribution is accomplished using the aforementioned rotary floor machine. The drive block transmits rotating motions to a bonnet made of cotton, rayon or a combination of both. During the agitation phase of soil extraction, the bonnet absorbs suspended soils. The rate of absorption must be monitored, and the pad must be turned over or replaced as significant soil accumulates. When both sides of the pad are soil-saturated, it must be replaced.

When the carpet is dry, further soil extraction may be accomplished when remaining detergents are extracted through dry vacuuming during daily maintenance. Again, a high-efficiency filtering system is recommended.

Anticipated dry time: one to three hours.

Shampoo Cleaning Method
Following vacuuming, a shampoo is distributed to the carpet and agitated with a mechanical brush. The shampoo and suspended soil are extracted by either a wet vacuum or through dry vacuuming.

When a non-foaming detergent is applied with a pump-up or electric sprayer, agitation is accomplished with counter-rotating, cylindrical brushes. Application through the shower or channel-fed brush is accompanied with uniform shampoo distribution, using rotating brush action at the recommended speed. Conditions may require multiple passes over heavily soiled and high-traffic areas.

Once shampoo application and agitation are complete, suspended soil extraction must be accomplished with wet vacuuming of excess shampoo and the suspended soil, using simultaneous or supplemental wet vacuum equipment designed for the purpose. Further soil extraction is accomplished once the carpet is dry and the remaining dry detergent residues, along with attached suspended soils, are vacuumed from the carpet during routine maintenance.

Anticipated dry time: drying must be accomplished within 12 hours.

Hot Water Extraction Method
Once vacuuming is complete, a cleaning product is applied to the carpet and agitated. The cleaning product is extracted by rinsing with water from a portable or truck-mounted extraction unit that may contain rinsing agents or emulsifiers.

In normal soiling situations, it is recommended that an appropriate cleaning agent be used during the injection phase of hot water extraction. This is essential for suspending soils. Heated pre-conditioners and rinse detergents increase detergent activity. A heated solution requires less detergent and minimizes residue. However, excessive temperature may cause accelerated color migration. Cut-pile wool and velvet-plush carpet styles may distort when excessive heat and injection pressure are combined.

Pre-conditioner application must be followed with uniform cleaning agent distribution using hand brushing or mechanical brush action. Such action may include the use of cylindrical or rotary brush agitation equipment. Additional agitation is achieved during the injection phase using solution pressure, or when using rotary extraction equipment.

Following agitation, suspended soil must be flushed from the carpet using hot water extraction equipment. Multiple passes may be required to rinse suspended soil from the base of yarns.

Anticipated dry time: complete drying must be accomplished within 24 hours. Additional procedures may be necessary to expedite drying.

For more information on these methods or any other area of carpet cleaning, contact the IICRC at (360) 693-5675 or online at

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