The Extraction Issue
Dec 1, 1997 12:00 PM, Richard Shaw
Over the years, there has been some controversy raging in cleaning circles about whether dry or wet extraction is the best method for cleaning carpets in educational facilities. Some maintenance managers swear by dry extraction, while others feel that wet extraction can provide the most benefits.
Dry vs. wet Dry carpet cleaning is a relatively new concept to most people, but actually it has been around for a number of years. The basic idea of the system has not changed much since its inception. The method employs a system where the worker spreads the dry-cleaning compound--a ground-up cellulose impregnated with special solvents--over a carpeted area. He or she then works it in with a special machine and vacuums it with a high-quality, high-suction, high-filtering vacuum.
On the other hand, people have known about wet extraction for a long time, but have not always thought of it positively. In the past, slow machines could create as much back-breaking labor as they saved. There was a time when wet extractors left carpet so wet that furniture could not be placed on it for two or three days. However, those times are now long past. Advances in vacuum and injection technology in the past 20 years have changed the process forever. Compact portables, which operate in smooth paths, have replaced the wet-extraction machines of old that used heavy hand wands.
Air-quality concerns Over the years, both wet and dry extraction have proven to be effective in different situations. However, the controversy centers around some other areas, including cost. Of all the arguments put forth about these systems, one seems to be the most prevalent among both end users and sanitary-supply distributors: Which type of program impacts the indoor air quality of a building the most, either positively or negatively?
Although not everyone agrees on the issue, several studies have been conducted concerning carpet and indoor air quality. A few years ago, carpet was cited as a reason for many indoor-air-quality woes plaguing buildings. Some schools and universities even took such drastic steps as to remove carpet and replace it with tile or hardwood surfaces, often finding that indoor-air-quality problems actually increased.
More recently, it has been suggested that instead of being a trap that captures harmful materials and then spreads them into the air, carpet could be a filter that holds the contaminants until they are removed by a proper extraction process.
One study monitored unclean carpet and found that the air monitors, which were located only two feet above the surface of busy, well-used building floors, picked up very little proof that the carpet puts anything into the air at all. The study suggested that carpet probably saves us from greater IAQ problems than we would experience with hard-surface floors.
This does not mean that IAQ can be forgotten when talking about carpet. The same study also pointed out that humidity actually is the biggest factor involved in creating IAQ problems when it comes to the carpet-cleaning process. This may seem like a reason to avoid wet extraction, but the system can work well if the carpet is dried properly after the process is completed. If cleaning personnel have soaked a carpet to clean it, and then leave it under the conditions in which bacteria grows, it follows that some type of growth will take place.
Making the system work Basically, it is important to remember that both wet- and dry-extraction systems are, after all, just tools to use in maintaining carpet. Neither are a substitute for each other in certain situations. Both systems have their place, depending on the type of facility, how much that facility is used, and what type of climate the school or university is located in.
Schools, colleges and universities are busy places, and while one system may be preferred over the other for institutional needs, there may be situations when one system is better suited. School districts need to find positive reasons to use any system that is available to solve their problems. Certainly, if there is a flood from a broken pipe or a carpet soaked from snow or rain, wet-extraction equipment is needed. Likewise, a busy residence-hall lounge that always has students in it and seems impossible to keep clean with wet extraction may make a case for the use of a dry-extraction system.
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