Facilities (Learning Spaces)

Keys to Healthy Carpet Care

Healthy Carpet Care


How do you keep carpet, one, clean, and two, healthy? Do number one and number two will follow.

Cleaning carpet means removing foreign matter including cleaning residues, leaving only clean carpet fiber, backing or flooring material.

Prevent dirty and unhealthy carpet using mats

Entrance mats prevent carpets becoming dirty and unhealthy by stopping dirt at the door. Use two mats — one outside and one inside — a bi-level outside scraper mat to remove gross soil, and an inside carpet-type mat with slip resistant backing (preventing mat ‘creep’) to dry shoes and remove finer contaminants.

Remove contaminants

Your carpet is an investment that can last a decade or more if you keep it clean. How? Remove the following;

  • Gritty soil that cuts and scratches fibers, by vacuuming daily or twice weekly in traffic lanes, and weekly to monthly in less-trodden areas, using a vacuum approved by the Carpet and Rug Institute (CRI).
  • Sticky soil via a hot-water, low-moisture extraction process using a fragrance-free, soap-free product, leaving nothing behind but restored carpet fiber and an untainted environment.
  • Moisture, aka water, using a low-moisture process and effective extraction using a carpet extractor approved by CRI.

When carpet is a filter — and when it is not

It has been said carpet acts as a filter, and it does to the degree that it captures particles and prevents them from getting airborne.

All too often, though, improperly cleaned carpet acts as a dust source when, like a too-full sink, it overflows and releases particles into the breathing zone of students and staff with every footfall across its surface.

Carpet dust consists of many pollutants, including allergens, paper and textile fibers, chemicals, pesticides, heavy metals and soap residues from “cleaning” products that leave sticky deposits on fibers.

Documenting and preventing airborne soap particle residue

One Eastern Washington State school district undertook an indoor environmental assessment, study, and intervention — by Indoor Air Quality (IAQ) consultant, Dr. Miles Athey — to protect and enhance the learning environment within the district’s elementary schools.

After investigating occupant complaints and testing many IAQ parameters, Dr. Athey concluded two factors were the most frequent sources of the IAQ problems: ventilation and carpets.


The ventilation issues were largely remedied with several adjustments: 1) spacers were added to close off gaps in the HVAC filter brackets, eliminating the passage of unfiltered air into rooms, 2) an array of different kinds of filters (including filtration of particles as small as 1 micron, drop-in HEPA filters for supply grilles, and carbon filters for odors) were adopted throughout the district, each designed to prevent specific air quality problems, and 3) air dampers were routinely recalibrated to coincide with the district’s computerized digital control system helping to ensure sufficient quantities of fresh outdoor air were supplied to each room.


An inconsistent cleaning program along with material, equipment and other deficiencies had apparently contributed to a significant buildup of soap residue on and between carpet fibers in the district’s elementary schools. This residue-particle loading in carpet was exacerbated by factors such as inadequately filtered outside air through HVAC systems, outside contaminants tracked in on shoes, improper products to clean carpets, and insufficient vacuuming and hot-water extraction of carpets, thus increasing respirable airborne particulates.

Measuring particulates — equipment and methodology

A MetOne laser particle counter was used to measure classroom particulate counts for particle sizes of 10, 7, 2.5 and 1 microns in diameter at carpet level in both the ambient (undisturbed) state and the aggressive (disturbed) state for 3 minutes. The aggressive sampling consisted of beating a square meter of the carpet surrounding the particle counter for the first 20 seconds of the three-minute sampling period. This forces particulates to dislodge from the carpet fibers and become airborne.

In most cases, the ambient levels were well below the EPA’s — then current — unhealthy Air Quality Index thresholds and were comparable with outside particulate levels. However, most of the aggressive samples were substantially higher indicating that the carpets were continually over-loading on particulates and thus were not being efficiently vacuumed or extracted by cleaning procedures. While the EPA’s Air Quality Index had cautionary statements for particulates of 2.5 and 10 microns in diameter at levels of 40 and 150 micrograms per cubic meter (ug/m3), respectively, these levels were considered to be more appropriate criteria for adult and industrial applications. The California Air Resources Board, as a result of that State’s Children’s Environmental Health Protection Act, had established more stringent criteria for children. These levels were adopted for the district’s IAQ program standards: 24-hour averages of 12 ug/m3 for PM 2.5 and 50 ug/m3 for PM 10.

Baseline measurements

The initial baseline particulate measurements were taken in carpeted classrooms of several of the district’s elementary schools while school was in session February-March. These rooms had been occupied since September of the previous year and had been vacuumed daily.

These data indicated that significant quantities of particulate matter had loaded into the carpets over time and the cleaning procedures were not getting the carpets as clean as desired.

Based on the data, the district began to
investigate its carpet cleaning procedures, and to search for a more efficient and effective cleaning process.

Dr. Athey speculated the extraction carpet cleaners previously and routinely used by the custodial staff were leaving solvents and soapy residues that the extraction process was not able to remove without using some other cleaning compound.

Another Washington State School District recommended a soap-free product as a means to break up the particulate-trapping residue.

Students in one classroom were relocated and a deep cleaning program was performed on this carpet. The soap-free product was applied to the carpet. After testing for particulate counts before and after the application, it was inferred that this product was able to chemically or otherwise separate entrapped particulates in the carpet from the fibers and backing without damaging the material or leaving resides, something other carpet cleaning products used were apparently unable to accomplish.

Carpeting was then deep cleaned using the soap-free product throughout the district. The same aggressive particle sampling procedure referenced above was used for measuring particulate loading in carpets, before and after the cleaning, in five classrooms.

Summary results

The greatest improvement was L4; PM10=69.9 ug/l before, 3.2 ug/l after — a 2184-percent improvement. The least improvement was P4; PM10=81 ug/l before, 8.4 ug/l after, a 964-percent improvement. For all five rooms sampled, the average percentages of improvement by particle size were: PM10=1582 percent, PM7=1620 percent, PM2.5=1737 percent, and PM1=326 percent.

Research Addendum Notes: The major apparent advantage of using a soap-free product for carpet care is that its active ingredients are inorganic. Other carpet cleaning products often use organic chemicals (solvents) that leave residues within the fibers. These residues actually increase the attraction and bonding of additional particulates into the carpet fibers. When mixed properly, the intervention solution forms a mild (degreasing) liquid that effectively dissolves bound organic particulates, releasing them from carpet fibers and backing without damaging the integrity or color of the carpet. The intervention is also non-toxic making it environmentally preferable for chemically sensitive individuals.

Dr. Miles Athey has written two dozen classified reports for the U.S. Navy and U.S. Army, contributed to dozens of engineering and environmental reports for industry and has been a principal author of over 50 environmental assessment/impact reports. He has also written over 300 technical articles on business, education, engineering, science and health. He has earned advanced degrees in several sciences including a PhD in environmental toxicology.

This article originally appeared in the issue of .