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Carpet Cleaning and IAQ

By Michael Hilton

Indoor air quality (IAQ) has become a major buzzword for the "90"s. Product claims for products that improve IAQ have grown exponentially, but not without attracting attention from the Federal Trade Commission (FTC) and other regulatory authorities. The FTC has been carefully perusing claims by products that claim to improve IAQ and has taken substantial action against numerous product manufacturers. While many products do provide some positive impact on IAQ, other products can be likened to the snake oil industry of the last century. Conversely, other products have been prematurely blamed for IAQ problems based on unsubstantiated evidence.

The problems originate with the study of IAQ itself. There are few hard-fast rules that receive universal acceptance throughout the scientific community. There are recommendations for airborne particles, bacteria, fungi, allergen, and chemicals, but these recommendations are based on a database of collected samples rather than substantiated health-based recommendations. This collected database has been divided into high, medium, and low concentrations, but these categorizations provide little insight into anticipated health responses. For example, many IAQ consultants recommend a total respirable indoor particle level of 50 micrograms per cubic meter of air (ug/m3), but stop short of suggesting that maintaining particle counts below this level will assure a healthy environment. For airborne fungi, the recommended indoor levels have been established at less than one-half the outdoor level. What is unclear about this strategy is why 251 colony forming units of fungi per cubic meter (cfu/m3) of air indoors is unacceptable in Dallas TX, where outdoor fungi levels may average 500 cfu/m3 and 1000 cfu/m3 indoors is acceptable in Florida where outdoor fungi levels may exceed 5000 cfu/m3. The study of IAQ has made dramatic strides over the past 10 years, but until direct cause and effect links can be established, it still must be considered a "work-in-progress".

With these realities in mind, it is difficult to evaluate the impact of flooring material on IAQ. Carpet has been frequently identified in unsubstantiated media reports as a contributor to airborne particles and allergens. Many of these claims have been based on the ease in which dust samples can be collected from carpet and evaluated. However, tracing the source of airborne allergens and particles back to carpet is far more difficult. Many allergists and IAQ consultants alike, assume that the presence of allergen in carpet suggests that carpet releases these allergens into the breathing zone. Recent studies do not support these assumptions.

In 1973 based on inaccurate data relating to the release of airborne allergens from carpet, the Swedish government banned the use of carpet in all public facilities. When allergic reactions dramatically increased, the ban on carpet was reversed in 1990

In 1973 based on inaccurate data relating to the release of airborne allergens from carpet, the Swedish government banned the use of carpet in all public facilities. When allergic reactions dramatically increased, the ban on carpet was reversed in 1990

Recent carpet cleaning efficacy studies, performed in an environmental chamber by Air Quality Sciences, Marietta, GA, (Carpet Cleaning and Acceptable Indoor Air Quality: A general review of Carpet cleaning Effectiveness, AQS Report # 02234-01D2) involving a complete battery of airborne evaluations revealed little, if any, airborne contribution from carpet typically found in a normal environment. However, in the same study, heavily contaminated carpet removed from an abnormal environment and incubated in high humidity (85-95% rH) conditions for several weeks, revealed significant airborne contributions from contaminants found on the carpet surface. One of the most intriguing findings of the study was the ability of carpet to "trap" contaminants found within the carpet pile, despite high contaminant levels. The study suggests carpet releases only those contaminants found on the carpet surface.

Another joint EPA/RTI study (Indoor Environment Characterization of a Non-Problem Building: Assessment of Cleaning Effectiveness) indicates carpets’ unique ability to lower airborne contaminant levels. This study (also called the Frank Porter Graham Study), and numerous other studies, indicated contaminant levels found within the carpet pile were significantly reduced following cleaning. Airborne concentrations also were lowered significantly following cleaning, but the levels found in the carpet pile increased quickly as airborne levels dropped, indicating a possible "filtering" effect. Carpet is a unique flooring system in that airborne particles and allergen can be removed from the breathing zone where they remain in the carpet pile. Carpet has the ability to filter airborne particles only until it becomes filled with soil, after which it takes on the characteristics of a hard floor. Vacuuming and regular cleaning can remove this accumulation.

Flooring Surfaces and Airborne Particles

Other studies have examined the relationship between various flooring surfaces and airborne particles including allergens. Recently, a study was undertaken in a south Florida school in which high humidity conditions contributed to extremely high dust mite allergen levels in the carpet. Allergen levels in the carpet dust were more than ten (10) times higher than accepted (based on an averaging of allergen levels found throughout the country) levels. Air samples were collected for 90 minutes while children were performing vigorous activities. No airborne allergen was detected at four inches, twenty-four inches, or forty-two inches above the floor. After school, a vacuum cleaner was disassembled and the dust containment system was removed to allow allergen and particles to be distributed directly into the air. Significant airborne allergen was detected at the three heights during the 90-minute vacuuming activity. After the allergens had settled to the carpet the activity was repeated with the dust containment system in-place. No airborne allergens were detected. This indicates the ability of carpet to trap these allergens and prevent their release under normal activities and demonstrates the effectiveness of vacuuming in removing these allergens without airborne release.

It is normally assumed that if allergen is contained within the carpet pile that this allergen produces allergic responses; however, airborne sampling does not indicate the release of allergen from within the carpet pile. Current sampling practices of evaluating allergen levels within the carpet pile do not provide an indication of anticipated allergic response.

Other studies have examined the relationship between various flooring systems and airborne particle levels. While many of these airborne particle studies contradict one another in terms of identifying which flooring material exhibits lower particle counts, research continues. Outdoor particle counts and the quality of indoor maintenance probably have far more impact on indoor particle counts than flooring type. Many researchers are only now beginning to examine the differences in particle levels generated as a result of maintenance activities between flooring systems. A few researchers have begun to question the impact of high particle count exposures on maintenance personnel.

Airborne particle exposure has become a major concern for the EPA and many IAQ consultants. We are only now beginning to understand the health effects of airborne particles

The carpet industry, through the Carpet and Rug Institute (CRI), always has assumed a proactive approach in regards to indoor air quality. In response to these concerns and the resolve that carpet produces fewer airborne particulates than other flooring systems, the CRI has launched the CRI Indoor Air Quality Vacuum Cleaner Testing Program. This program, while in no way intended to be viewed as a health standard, establishes performance standards for vacuum cleaners. This voluntary testing program establishes benchmarks for vacuum cleaner performance in soil removal efficiency, particulate emissions or dust filtration, and damage to carpet pile fiber.

While the primary reason to purchase a vacuum cleaner is to remove soil, through the testing program the carpet industry quickly learned that some vacuum cleaners can be very destructive to pile fibers. Other vacuums that make boastful claims of high particulate filtration or HEPA filtration remove very little soil. With these findings the CRI established very strict standards for each of the three program areas. To display the green CRI label a vacuum cleaner must meet published guidelines for each of the three criteria. Less than half of all vacuum cleaners tested meet all minimum performance criteria.

The importance of meeting each of the three criteria may not appear obvious. The performance of a vacuum cleaner that produces low particle emissions but removes little soil may be improved by installing a stiff brush roll which removes additional soil. Unfortunately, a stiff brush roll may damage pile fiber. Also, the performance of a vacuum cleaner that provides poor filtration but good soil removal may improve filtration by using more efficient bags. Again, more efficient bags may reduce airflow and reduce soil removal efficiency to an unacceptable level.

The CRI Indoor Air Quality Vacuum Cleaner Testing

The CRI Indoor Air Quality Vacuum Cleaner Testing Program has been designed with the end-user in mind. It has been developed to provide the consumer with an informed comparison between vacuum cleaners. The program’s objective is to encourage improvement in the performance of vacuum cleaners while reducing particulate emissions. However, since it is a voluntary program for vacuum cleaner manufacturers, the consumer must request vacuums which display the green label in order to ensure the programs continued success.

Does carpet cleaning affect IAQ?

Does carpet cleaning affect IAQ? The executive summary answer would have to be emphatically – yes!….. and no. To suggest that carpet cleaning is the end-all answer to poor indoor air quality would be a bit egocentric. Carpet is only a very small part of the equation as it pertains to indoor air quality. The indoor environment is a very complex network of interrelated systems. In suggesting that carpet cleaning alone, improves or cures indoor air quality problems would suggest that carpet, alone, is the source for these indoor air quality woes. If carpet were the source of these complaints we would expect to be able to replace carpet with another flooring system and resolve all IAQ complaints, but this strategy rarely works to cure anything more than psychological ailments.

We know from the work of allergists, who recommend the removal of carpet from bedrooms on a daily basis, that replacing carpet will not resolve allergic symptoms. If the answer were so easy, why do patients continue to see their allergist after carpet removal? Likewise, several Florida school systems found that biological problems did not disappear after carpet replacement and many of these same school systems are reinstalling carpet for acoustical and aesthetic reasons.

Perception, based on opinion, rather than scientific fact that carpet negatively affects IAQ is difficult to overcome. Various companies are perpetuating this belief by selling their products and services as a method of alleviating problems attributed to carpet. Many of these companies have received their total subsistence from carpet for two generations or more. Others simply see an opportunity to "cash in" and "cash out".

This perception is becoming firmly rooted in a large percentage of consumer minds. Recently, during an IAQ presentation to a very large northeastern school district, school officials stated that their future plans did not include carpet, based on IAQ complaints. It seems the school district had more than 200 schools and 19 carpeted schools were suffering from IAQ problems. After further questioning, it was learned that 39 of their schools had somewhat serious IAQ complaints but only 19 used carpet. When asked for an explanation of why they attributed the problems in carpeted school to flooring material and problems in the 20 other schools to "unknown" factors, their answer was based on newspaper accounts, parental concerns, and general perception based on anecdotal beliefs.

Would carpet cleaning alone resolve these IAQ complaints?

Absolutely not! But carpet cleaning in conjunction with a facility-wide maintenance plan may help.

Several field studies have been performed by the Carpet and Rug Institute, involving carpet cleaning and its affect on IAQ. We were looking for a direct cause and effect relationship. In other words, measure airborne biologicals before cleaning and after cleaning, subtract one from the other, establish the amount of improvement, and credit carpet cleaning. Unfortunately, early on, we did not understand the complexity of the indoor environment. Carpet cleaning did not produce any measurable impact on the amount of airborne biologicals.

A two-year study was then initiated to install a "quality" maintenance program in a south Florida classroom and monitor biologicals in carpet dust and those airborne above carpet over the two-year period. Through a quality vacuuming and carpet cleaning program, we were able to lower biologicals in carpet dust by more than 99% but airborne biologicals were unaffected. We assumed our study was flawed. We could see no reason why reducing the biological load in carpet by more than 99% should not impact IAQ. We later learned that our study was not flawed but rather assumptions we had made were flawed.

We assumed, like many IAQ consultants, that the biologicals in the air above carpet must be released from the carpet. Assuming that removing the contaminants from the carpet would improve IAQ was egocentric on our part. In reopening the data more than a year after the study was completed, we began to note similarities with other studies we were performing. We later learned that indoor airborne biologicals were a direct result of outdoor levels. Thus during cleaning with the HVAC in operation would not indicate a reduction in airborne biologicals because the HVAC system was continuously introducing more biologicals. This Florida study in combination with data from other school studies and chamber data has convinced us that carpet does not affect IAQ – IAQ affects carpet.

About the Author
Michael Hilton was the original creator of Carpet Buyers Handbook. Having owned and operated a carpet wholesale company, Hilton has a vast knowledge about all-things carpet related as well as other types of flooring.

Other Helpful Links
Cleaning Challenges
Carpet Cleaning and IAQ
Carpet Cleaning Myths
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