The Science of Carpet Cleaning: How It Works

INTRODUCTION 

In a broad sense, carpet cleaning includes two things. Such as-

Observe and evaluate/analyze the carpets: Includes the fiber type, color, age, high traffic areas, dirt and debris type, stain types, soiling type and condition, fungus and mold growth, contamination type, volume of the mess etc.

Cleaning the carpets: Includes different cleaning products (chemical, organic, commercial, homemade, dry cleaning agents, encapsulants etc.), cleaning methods (all the methods written by alldiysolutios.com), cleaning devices (shampooers, steaming machines, vacuum machines, cleaning wands etc.), pre-treating old and stubborn stains, using the machines properly, spot testing with different cleaning products, repeating the process if necessary, preparing the home made solutions with right ratio, executing the methods properly, using enough water, not overusing water and cleaning products etc.

Carpets get dirty and weird quickly (within a short term use) because of the following reasons-

• Not cleaning them routinely 
• Not vacuuming on a regular basis.
• Not treating the high traffic areas
• Not Cleaning The Stains Immediately when they are fresh
• Not using door mats or, rags

As carpet cleaning becomes a part of hygiene inside home, we must do it in a proper scientific way. Otherwise, all those efforts and hard work will go in vain. Such maintenance includes time sense, planning for the task, recommended chemicals and cleaning devices, other requirements and supplies needed. Here, we can gladly tell you that all our contents and articles are based on profound scientific research (peer reviewed journals). Also, we’ve cited all those secondary resources and shared the references with you. So, we can request you with confidence to follow all our contents and carpet cleaning procedures for better results.     

Carpet Soil 

Carpet soil refers to deposition of unwanted and unexpected substances on the carpets and gets trapped there. 

These unwanted substances include suspended particles (dust, silt), loose hair and fibers, organic matter (human waste, pet urine and faeces), feed particles (human and pet food, juice, soft drinks, and wines), oil, grease, wax, gums, paints etc. Among these carpet soiling substances, some are water soluble and some are water insoluble matters. So, you have to determine the type first and then choose a carpet cleaning method with the right cleaning products and equipment.  

Prevent soiling:

First, find out the sources of carpet soiling and the soil type, and then decide how to handle and solve this issue. You cannot stop the problem of carpet soiling permanently, because it is a daily occurrence. All you can do is prevent this soil or, dirt accumulation by some simple strategies-

• Maintaining the exterior walkways periodically 
• Use entry mats or, rags inside and outside the house
• If you maintain the exterior walkways properly with entry mats and barrier matting systems, you will be able to prevent the fast and heavy soiling on your carpets.

In such cases, you have to focus on vacuuming, brushing, and cleaning these entry mats routinely. 

Sources of soiling:

The sources from where soils accumulate and trapped on your carpets are-

• From the outside or, surrounding your home, several particles like mud, sand, clay, dried leaves, and dust enter into the home along with airborne pollutants and trapped in the carpet fiber. 
• Some common sources are animal and human dander and hair, fibers from paper goods and fabrics, human and pet body oils and food particles.
•  Another significant source of soiling on carpets is from the kitchen and dining areas inside every home. These sources include edible oils, raw vegetable wastes, fat and other food wastes etc.
• Strong winds blow light and heavy dust particles inside home and deposition on every surface especially the carpets.

Types of Soil: 

For effective cleaning the chemical and physical properties of different soils must be known and understood.

• Water-soluble soil: This type of soils dissolves in water easily and can be cleaned quickly from carpet with less effort. Some examples are- sugar, salts on urines, body fluids etc. 

• Dry solvent-soluble soil: This type of soils includes tar and grease from vehicles and garages, animal and vegetable oils produced during cooking food in the kitchen. If such oily soils accumulate on the carpets and are not cleaned immediately then they will dry out and sit permanently in the deep carpet fibers. Also, many stubborn yellowish or brownish stains resemble on the carpets, which are really tough to remove. With appropriate cleaning products and pre-treatment methods these messes can be cleaned at home easily. 
• Insoluble soil: These soils are insoluble or don’t dissolve in water and normal chemicals used for cleaning. That’s why they must be cleaned with specific manners different from usual cleaning. Insoluble soils on carpets include clay, sand, limestone, quartz (silica), gypsum, carbon etc. Also, paper products, cloth fibers, protein fibers from pets and humans etc. are considered as insoluble soils when deposited on the carpets.

Composition and sources of different types of soil from carpets:

Insoluble soil:

Composition: Clay, sand, quartz, carbon feldspar, gypsum, Protein fiber, Cellulosic matter and fiber.

Sources: Tracked from exterior (grass, leaf fragments); shed from newspaper, magazines, paper, clothing; interior plants.

Water-soluble soil:

Composition: Sugar, starch, salts, fluidic residues

Sources: Foodstuffs, body fluids

Dry solvent-soluble soil:

Composition: Tars, asphalt, animal and vegetable oils

Sources: Tracking, cooking vapors, body oil (human & animal)

Moisture: 

Composition: Humidity

Sources: Outside air; inside activities

Soil Buildup:

Soil accumulation starts at the entry areas (high traffic areas) first. When entry areas get saturated soiling starts to sit persistently in the deep carpet fibers. Eventually, the whole carpet starts to become heavily soiled if they are not treated in time. That’s why, the entry areas or the high traffic areas need to be well maintained by barrier matting or, using rags before stepping on the carpets. 

Soil accumulation on carpets occurs on three levels/layers.

1. Light and sticky soils such as hair, cellulose, dust etc. accumulate at the upper surface within the carpet pile.
2. The mid level contains relatively heavier soil particles like fiber and vegetable matter. 
3. The lower level contains the heaviest soil particles like sand and grit which damages the carpet most. Also they are tough to clean.

A review of literature on soil’ done by Dr. Al Luedtke in 1997 is summarized as follow- 

Plenty of studies conducted on soils from different parts of the world have shown that it is remarkably similar in makeup or formation. 

The soil is mostly consists of-

• 60% inorganic salts (silicates, phosphates, etc.), 
• 20% fiber (animal and cellulosic)
• 15% macromolecular organic components (resins, gums, etc.) and
• 3-5 % lowers molecular weight organics (non-volatile greases, fats, and oils). 

The binding of soil particles to the carpet fibers is ascribed to 3 mechanisms. Such as-

1. Occlusion in the fiber surface structure and within the fiber bundle
2. Electrostatic forces and 
3. Oil binding: The particles embedded in a soft organic matrix. 

Most researchers concluded that the oil binding mechanism is mostly responsible for soil accumulation and deposition on deep carpet fibers. Also, such soiling on carpet is hard to clean.  The first two mechanisms occur certainly but the forces that are holding soil particles in the carpet fiber can be easily cleaned or vacuumed by routine cleaning. 

The first contact of the soil particles with the carpet fibers is appeared to be by foot traffic. Most studies concluded that 80% soiling is associated with shoes (foot traffic) and 20% is associated with airborne ways. 

Preventive Maintenance: 

To prevent heavy soiling on your carpets you have to vacuum them routinely beside entry maintenance and barrier matting. 

 You cannot remove all the fine particle soils from your carpets if they accumulate slowly in the deep carpet fibers. 

Heavy soiling not only affects the appearance but also starts to damage the building materials of the carpet.

That’s why your carpets should be vacuumed regularly, otherwise soil accumulation and damage of the carpet fibers are inevitable. 

There are two types of vacuum machines-

1. Canister vacuum machine: they are designed for vacuuming drapery, upholstery and hard surfaces. They are not that effective at removing soils from carpets.
2. Upright vacuum machine: they are specially designed for removing maximum dry soil from carpets. The brush-bar of upright vacuum machines combs out the loose hair, strings and lint. The air stream generated in these vacuum machines can easily lift and suck up the dust, sand and grit trapped in the carpet fibers. These sucked up soil particles are then stored or deposited in a disposable recovery chamber or bag. Without this high-efficiency disposable chamber, the vacuumed up soil particles, especially the dust will pass through and deposit back on the carpets as well as the other surfaces inside home.

We recommend thoroughly vacuuming your carpets twice a week. It will prevent soils from sitting downward or in the deep carpet fibers. High traffic spots should receive repeated back and forth vacuuming each time. 

Particle Size of Common Soils:

Particles that range from 0.3 to 5 micron size remain suspended in the air for several minutes to days. They continue to be breathed in by the occupants or cleaning personnel.

Human lungs and bronchial passages are lined with ciliated surfaces (hair-like structures). These hair-like structures are capable of capturing and filtering the inhaled particles that are smaller than 10 microns. 

Smaller particles (<10 microns) can deeply penetrate within the lungs to the alveoli. Alveoli transfer oxygen from air to the body’s circulatory system through delicate membranes. When small particles are trapped and penetrate into deep lung tissues, they cause irritation and respiratory problems to the individual. Similar thing happens to cigarette smokers. 

During routine cleaning, consideration should be given to the breathing bioaerosol particles like bacteria, fungi spores or fragments and their metabolites (endotoxins, mycotoxins). Because, during vacuuming they become airborne and remain suspended for several minutes. And if inhaled by any person, may suffer from many bronchial diseases. 

For this reason, high-efficiency vacuum cleaners with disposable bags are essential for routine cleaning of your carpets.  

A list of common soils with their particle size that are found in the carpet is given bellow-

Airborne Particle Size Range in Microns 

Tobacco smoke: 0.01 to 1.0 

Combustion smoke (wood, etc.): 0.1 to 4.0 

Atmospheric dust: 0.01 to 1.0 

Household dust: 0.01 to 300.0 

Skin flakes: 1.0 to 10.0 

Insecticide dust: 0.1 to 10.0 

Fumes: 0.1 to 1.0 

Fungi spores (mold, mildew): 3.0 to 30.0 

Bacteria: 0.1 to 10.0 

Virus: 0.03 to 0.25 

Pollen: 10.0 to 100.0 

Hair: 30.0 to 120.0 

Particles below 0.2 microns are visible with an electron microscope (0.001 to 0.2 microns). Particles >0.2 to 10 microns are visible with a microscope. Particles >10 micrometers are visible to the naked eye. (Source: Stanford Research Institute)

Principles of Cleaning Carpets:

Carpet cleaning refers to the activities of removing/cleaning dust, dirt, contaminants and undesirable substances that are trapped or deposited on carpet fibers. Carpet cleaning includes locating, identifying, loosening, removing and properly disposing the filths or unwanted substances. DIY carpet cleaning can be accomplished on three levels-

1. Housekeeping – Keeping your house organized is an important factor for maintaining your indoor carpets. Housekeeping requires routine activities, skills and labor. Routine activities include emptying trash, dusting furniture, vacuuming carpets, mopping floors and other daily activities.
2. Maintenance – to perform these routine activities (housekeeping) you will need some machinery (vacuums, cleaning machines, air filters) or equipment, cleaning products (chemicals, solvents, detergents). These machines and equipment should be maintained properly for effective results.  
3. Restoration – This stage includes deep cleaning and other periodical activities. Restoration is needed when the soiling on carpets creates bad odors, unhygienic and irritating living conditions at home. In such situations, you need to deep clean your carpets to bring back freshness and a healthy environment inside your home. Restoration activities are not normal cleaning processes performed at housekeeping. These activities require knowledge and skills.  

[When someone cleans his carpet, he must emphasize on regaining the healthy condition of the house rather than visuals. We, the DIY solution team, think that the result of visual appearance after cleaning your carpets is desired by all, but the principal/primary goal should be your health’s safety. Fortunately these two goals (visual results and human health) can be achieved at same time with proper cleaning methods, products and equipments. ]

Principles of Cleaning – Five Major Components 

1. Dry Soil Removal Principle: Removing dry soil from the carpet (by vacuuming or brushing) is the first and essential step before starting wet cleaning or deep cleaning.

This step is accomplished in four phases (one preparatory phase and three physical removal phases). 

• Preparatory phase: First, pile preparation (using grooming tools) to untangle the pile of some high-pile residential carpet may be necessary before dry vacuuming. With commercial carpet, pile preparation simply is not an issue. 

Three Physical soil removal phases (phases of vacuuming): 

• Vacuuming the whole carpet with an upright vacuum machine.
• Hand vacuuming the entry areas and other high traffic areas.
• Vacuuming the edges periodically to remove the fine dust and soils from the carpet that the upright vacuum machine was unable to remove. 

2. Soil Suspension Principle: After removal of dry soil from the carpet it is time to begin with the soil suspension procedure or pre-conditioning. Soil suspension procedure is considered as the critical step in carpet cleaning by the professionals. Soil suspension helps to separate the soil particles from the deep carpet fibers. 

Soil suspension principle includes four fundamental factors. Such as chemical action, heat or temperature, agitation and time. They are discussed as below- 

3. Chemical action: Chemical action refers to the use of cleaning products like detergent, dish soap, vinegar, baking soda, borax, hydrogen peroxide….. etc. It is a fact that without a specific cleaner it is not possible to clean carpets at satisfactory level.  Without a carpet cleaner only physical damage of the carpet fiber or removal of a little amount of soil happens which makes the carpets messier. 

Chemical activity includes two phases of the cleaning process. such as- 

• Firstly chemicals or different cleaning agents are used to clean the carpets by reducing surface tension, dissolving, emulsifying, suspending, and sequestering all types of soils. This step is called pre-conditioning which is essential for quality cleaning.
• After dissolving the dirt and soils on the carpet surface the chemicals then make it easy to separate and remove them. 

4. Heat or Temperature: Warm water enables faster and more efficient cleaning of carpets than cold water. Because, heat reduces the surface tension of water which triggers the cleaning process. Also, heat can accelerate the activity of different chemicals that are used in carpet cleaning.   

Latest truck-mounted extraction devices are able to generate a safe and consistent water temperature (more or less 2000 F or 930 C) at the machine. This heating feature of different devices has made the carpet cleaning easier than ever before. If a consistent and optimum temperature is maintained during the cleaning process then it will bring best results and won’t damage the carpet fibers. Also, these machines have features for automatically controlling the temperature at a suitable range for the whole operation.  

5. Agitation: Agitation is important for uniform penetration and distribution of chemicals or cleaners in the carpet fiber. Without this step, soil suspension does not get done uniformly.

Agitation includes two phases in the soil suspension process. Such as- 

Hand brush agitation: Using a bristled brush or comb for pre-conditioning the carpets is an effective, time-efficient and less aggressive process of agitation. Brush agitation enables proper pre-conditioning of carpet piles in the high traffic areas like the entry, pivot, and heavily soiled areas. 

Mechanical agitation: It involves the use of mechanized nylon-bristled brush to achieve aggressive agitation and distribution of chemicals or cleaners into the carpet pile to ensure maximum soil suspension. 

6. Time: Residential or household carpets are cleaned on average once or twice a year. Soils that deposit during this time don’t get suspended in seconds, even with the best and strongest chemicals. But the good news is if you give 20 to 30 minutes (required) with the good chemicals then it is enough for a proper cleaning. Within this time the chemicals will be distributed on the whole carpet through agitation and loosen up all the dirt and stains for removal.

Recovered Waste Disposal: 

To dispose of the recovered cleaning wastes from carpets have five important areas to concern. They are discussed below-

1. Synthetic Fibers:

During deep cleaning or extraction cleaning of synthetic fibered carpets, shedding of synthetic building materials happens. These synthetic fibers are non-biodegradable and long durable materials. They cause further problems in treating sewage systems. Such fibers must be pre-filtered from carpet wastewater before disposal. 

2. Dry Solvents:  

If there is dry solvent spotted on the carpet before cleaning by a volatile or non-volatile spotter, then inevitably some of these chemicals will recover with several methods of carpet cleaning. Presently, science has evolved to molecular level where measurement in parts per billion (ppb) is possible. So, smaller or larger amount of dry solvent present in carpet fibers can be measured. People use alcohol or citrus solvents in the spotters to reduce this problem.

3. Pesticides:

Exterminators routinely spray residual pesticides on carpets to resolve household maintenance problems. During vacuuming or rinsing the carpets and extracting the pile yarns, some of those pesticides recover and deposit in recovery bags, tanks or canisters. So, wastes that contain pesticides in it must be treated properly before disposal.

4. Lead Particles: 

Trace amounts of lead have been found in laboratory analysis of waste water samples collected after hot water extraction (HWE) of carpets. The sources of lead contamination are paints, gasoline, grease etc. Lead particles are also measured in parts per billion (ppb) like dry solvents. Such toxic wastes need to be treated before dumping. 

5. Phosphates: 

Non-biodegradable phosphates that are disposed of in a water body, serve as fertilizers that cause phytoplankton bloom. This phenomenon is bad for aquaculture and living organisms on water.

There are two scientifically accepted methods for waste dumping. Such as- 

• A sanitary landfill 
• A sanitary sewage system. 

Solid wastes that are recovered during vacuuming and cleaning carpets at home contain trace amounts of the above discussed contaminants. They can be easily dumped in sanitary landfills to avoid environmental pollution. 

Liquid wastes like dry foam, shampoo, detergent, dish soap, steam extractions etc. are best to dispose through the sanitary sewer system after treatment. Sewage systems include pipe lines of toilets, washing machine drain lines, car wash drains and other drainage systems.