Moisture that comes from over-wetting is more likely to travel downward and condense under the carpet than evaporate into the air. And when it reaches a carpet's backing, any number of problems can result:
All of these problems are cause for concern, but the growth of mold and mildew can be the most serious because of the poor indoor air quality and health repercussions that can result. There are more than 100,000 different types of mold and mildew, and we are exposed to them all the time. Some have no effect on us, but others release toxins, and these can cause allergic reactions and illnesses, most specifically asthma.
According to the American Lung Association, more than 25 million Americans have been diagnosed with asthma. Some school districts have seen as much as a 160 percent increase in childhood asthma in the past 20 years, causing more than 14 million missed school days. And, it is estimated that more than 14.5 million workdays are lost because of asthma, much of it the result of airborne mold and mildew spores.
Once a mold problem develops in carpet, removing it can be a problem. Cutting off mold's food supply, which is essentially the moisture that caused it, is the best line of defense. For professional carpet cleaners, this suggests that using low-moisture carpet cleaning equipment and systems is not only the best defense but the best offense as well, preventing the formation of mold and mildew in the first place.
According to Williams, with some carpet cleaning methods, especially shampooing and bonnet cleaning, the skill and diligence of the carpet cleaning professional can be crucial. They can determine just how well the job is performed and how much moisture is released into the carpet.
Absorbent Dry Compounds. This is the "driest" way to clean carpets because no moisture is used at all. Dry compounds containing detergents or solvents are sprinkled on the carpet. After up to 30 minutes of dwell time, these detergents or solvents dissolve oil films on carpet fibers, freeing the soil to be vacuumed out along with the compounds. Often this method is used in schools or public facilities where drying time is at a minimum. There is no danger of over-wetting with this method, but, although it can produce satisfactory results, some professionals find the method labor intensive and often more thorough carpet cleaning methods will eventually be necessary.
Foams contain very little moisture, making it unlikely that over-wetting can occur. The foam is generated inside extraction equipment by mixing cleaning solution and air under pressure. It is brushed into the carpet fibers and then vacuumed out. But with this method, Williams says that the low moisture content may be too little to remove soil in the cleaning process. "Additionally, some foams may not vacuum out, which can interfere with later attempts to clean the carpet using other methods," Williams adds, "and the chemicals can actual ‘trap' new soil into the carpet's fibers."
Shampoo and Bonnet. Though different, both of these systems use a rotary brush machine to clean carpets. With the shampoo method, cleaning solution is released into the carpet through an opening in the rotary brush, which converts it to foam as it penetrates carpet fibers. There is a possibility that carpets can be damaged with this method by distorting carpet fibers. Experienced operators are essential. The chemicals used can deodorize carpets, retard future soiling, brighten the carpets, and speed drying.
With bonnet cleaning, an absorbent pad, or bonnet, is attached to the rotary machine. A detergent is sprayed over the carpet, or the pad is soaked in a detergent solution and then rotated over the area to be cleaned, removing soils that adhere to it. After employing either system, the carpets are vacuumed to remove any remaining soils or chemicals.
"Both of these methods are commonly used in commercial office buildings, especially in hallways and meeting rooms," Williams said. "They're quick, require just a rotary floor machine, and, if done properly, introduce only low moisture. But problems can occur, especially if low-quality detergents are used. The professional may need to re-clean certain areas to remove stubborn soils, causing increased moisture and overloading the carpets with residues that accelerate re-soiling."
Hot-Water Extraction. "In most cases, even if other carpet cleaning systems are used, carpets will eventually need to be cleaned using the hot-water-extraction method," Williams said. "Most experts will agree that this is the most effective and often the safest way to clean carpets."
With hot-water extraction, a pre-spray is used to loosen the soil, followed by hot water being injected into the carpet under high pressure and then removed along with loosened soil. The heat of the water is important. Studies dating back more than 100 years report that the effectiveness of the cleaning increases as the heat exceeds 200 degrees F. Additionally, the heat can facilitate drying, decreasing the possibility that too much moisture will be left in the carpets.
A decade ago, many carpet extractors used too much water to clean carpets or had poor vacuum capability. The result was often over-wetting. In the past few years some manufacturers have introduced low-moisture extractors that use as little as 0.8 gallons of water per minute. Some of these units also incorporate agitators that gently loosen soil.
The certification criteria include the issue of water recovery in carpet extraction equipment specifically because of the potential for mold to develop. Additionally, CRI believes too much water left in the carpet negatively affects its appearance and can damage carpet fibers.
Five truckmount machine manufacturers and one manufacturer of portable hot-water extraction equipment received the CRI seal of approval. "This program is significant for a variety of reasons," Williams said. "It's pushing the industry to develop more effective cleaning equipment to meet the cleaning needs of the customer, and because several carpet manufacturers plan to require [as part of their carpet warranties] that CRI-approved products and equipment be used."
This is a significant development for the entire carpet industry as well as the manufacturers of hot-water extraction equipment. But the best thing is that the consumer wins with better-maintained carpet along with a longer carpet life and better appearance.
As most of the cleaning industry becomes "greener," reducing the impact of cleaning on the environment, expect the use of low-moisture carpet cleaning systems to become much more commonplace.