Tamarack Environmental Inc. Case Study
Carpet Microbial Levels in the Workplace
Purpose: This case study is designed to show that with the use of proper cleaning equipment and procedures that the microbial loading in carpeted floors can be greatly reduced.
The building owner/manager can have an effective tool in the control of indoor air quality problems related to microbial loading in carpet when proper carpet cleaning equipment is used. Proper cleaning of carpet will also increase the useful life of the carpet.
The Cleaning Machine: The CFR "ALTRA 400 O-Z, SP" is able to inject cleaning solution into carpet under a pressure of 400 pounds of pressure per square inch (psi). The "ALTRA 400 O-Z, SP" also is able to instantly recover up to 98% of cleaning solution, so carpets dry in about an hour.
The Benefits: The "ALTRA 400 O-Z, SP" which uses ozone to assist in the cleaning process offers several benefits to building owners, managers, and others.
Can result in tremendous savings because carpet lasts much longer and does not need to be
replaced as often.
Makes carpet look like new again and greatly increases its life expectancy
Will effectively remove microbials (mold, fungal) spores from carpet.
Excellent soil removal, quick dry times and cost savings
The Case Study: The case study was conducted with the assistance of Paul J. Ellringer P.E., CIH and Dr. Chin S. Yang Ph.D.:
Paul J. Ellringer P.E., CIH, is a Registered Professional Engineer and Certified Industrial Hygienist, from Tamarack Environmental Inc., 1640 Scheffer Ave., St. Paul, MN 55116, (651) 696-0267. Mr. Ellringer was hired by the building owner to conduct this testing.
Dr. Chin S. Yang, a Ph.D. microbiologist, has been involved in indoor building related microbiological contamination for 12 years. Dr. Yang worked for the U.S. Public Health Service on microbial contamination until April of 1994. He is currently the Director of P ~ K Microbiology Services.
All case study microbial analysis testing was performed under the direction of Dr. Chin S. Yang at:
P & K Microbiology Services
1950 Old Cuthbert Road, Unit #L
Cherry Hill, NJ 08034
(609)427-4044
Building Characteristics: The building is a Minnesota Metropolitan single story school with about 2,000 students. The office suite has private office areas which each measure about eight feet on a side.
Problem: About two years ago, one of the staff started having respiratory distress whenever working in their off1ce. Several indoor air studies conducted over a two-year period were not able to determine the cause of this teacher's respiratory distress. Traditional indoor air quality parameters did not identify the concern. Three months ago Tamarack Environmental Inc. was asked to evaluate this office. As a part of this investigation micro vacuum carpet dust samples were analyzed for microbials (mold, fungi, bacteria, etc.). The microbial levels in the carpet in this office were very elevated compared to other adjacent offices at this location and also several other locations in this building. The elevated microbial present in this carpet was primarily the fungus Aspergillus versicolor. Aspergillus versicolor has been associated with occupational asthma and hypersensitivity pneumonitis reactions in office occupants. Aspergillus versicolor has also been shown to be an opportunistic pathogen and can cause upper respiratory infections in immune suppressed people. Moisture tests conducted also showed that the moisture levels in the concrete slab below the carpet in this off1ce and one adjacent of fice were elevated and the likely cause of the increased microbial levels in the carpet.
"Several cleaning methods were implemented to improve the situation. Replacing the carpet in the private offices was an option, if the microbials could not be controlled. This carpet was less than four years old."
From October to December, 1998, three different methods, by different vendors, were undertaken to control the microbial problem. The third method provided excellent results.
The first method involved vacuuming the carpet and then cleaning it using standard hot water extraction techniques used in the school district. Microbial tests conducted within a week after this was done showed that the microbial levels had doubled.
The second method involved HEPA vacuuming of the carpet and then the spraying of OxineTM onto the carpet. OxineTM is a strong bleach like solution. Microbial tests conducted within a week after this was done showed about a 50 percent increase in microbial levels. The microbial levels now were three times higher than when this process started. The staff person's health problems were not any better.
The third method involved the use of a CFR "ALTRA 400 O-Z, SP" ozone assisted cleaning system. Based on before and after microbial tests the "ALTRA 400 O-Z, SP" was able to remove 93 to 99% of the viable microbial spores from this carpet. The "ALTRA 400 O-Z, SP" is a cost-effective way to reduce the microbial loading in carpet and provides the building owner/manager and others with a new option in the fight to improve indoor air quality (IAQ).
Testing Procedure: Determining the microbial loading of carpet has been difficult in the past. Tamarack Environmental Inc. working with Dr. Yang of P&K Microbiology Services and the U.S. EPA has recently developed a test method which works very well. This test method is called microbial micro vacuum carpet dust sampling. The U.S. EPA first starting using a method similar to this about five years ago to test carpet microbial levels. Since then this method has been refined and used extensively to test carpet. Tamarack has collected more than 1,000 samples using this method over the past three years. The State of Minnesota is presently using this method to test carpet microbial levels. Carpet dust samples are collected using a three-piece 37 mm cassette with a 0.8 llm pore size mixed cellulose ester (MCE) filter. The samples are collected using a vacuum pump at a flow rate of 15-30 liters per minute through the filter. The filter cassette is used open faced. The samples are collected open face (top of filter cassette is removed) with one square foot of the carpet being vacuumed. A vigorous collection method is necessary. The filter cassette needs to be pressed with some force onto the surface of the carpet. The same one square foot of carpet is vacuumed at least three times. The filter cassette needs to be closed and then tapped lightly. If debris rolls around in the cassette and has a volume at least equivalent to two peas, sampling is complete. If enough debris has not been collected, a second square foot of carpet will need to be vacuumed. Filter cassettes need to arrive at the laboratory within 24 hours of sampling or be refrigerated. Under no conditions should the samples arrive at the laboratory more than five days after collection. MCE filters are removed from the cassettes holders and the loose debris weighed, and then suspended in sterile distilled water, diluted serially (three dilutions minimum 100, 1640, & 4100X), and inoculated onto 2% malt extract agar (MEA) plates. The MEA is suitable for general fungal and yeast isolation and growth.
Test Locations: Two private of fices and a hallway were chosen as the sites for microbial testing before and after the cleaning of the carpet using the "ALTRA 400 O-Z, SP".
Sample Location 1: Private office - initial test results were:
- 267,000 colony forming units per gram of carpet dust (CFU/g) Alternaria (7%), Cladosporium (59%), Epicoccum nigrum (21%), Penicillium (7%), & yeasts (5%)
Within a week after cleaning
- 4,400 CFU/g - Alternaria (25%), Cladosporium (25%) and sterile fungi (50%)
Reduction - 98%
