Airborne Dust - Is There More from Carpet or Hard Floors?

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A series of experiments were conducted to determine airborne particulate emissions during a variety of normal activities on hard and carpeted floors. Surfaces were uniformly seeded with test dust. Activities tested included: dust mopping a hard surface; vacuuming a carpet with a Carpet and Rug Institute (CRI) Green Label-approved vacuum; vacuuming a carpet with a non-CRI-approved vacuum; walking on a hard surface; and walking on a carpet.

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For the dust mopping experiment, dust was first permitted to settle for fourteen minutes, at which time no airborne particles (0.0 micrograms/meter3) were detected. Dust mopping was begun at a walk rate average of 3.8 feet/second. At 30 seconds of dust mopping, the airborne particulate count rose to 46.2 micrograms. At 1 minute the airborne particulate counts increased to 353.9 micrograms/meter3. The airborne particle counts rose steadily until at 11 minutes of mopping a peak concentration of 2032.9 micrograms/meter3 was detected.

IICRC Comments

According to IICRC technical advisor Jeff Bishop: "Carpet often actually improves indoor environmental quality by trapping and holding particles, dust and other soils until routine maintenance and cleaning can remove them. However, if neglected, carpet, like any container, can become filled to the extent that it can hold no more. At that point - when the surface is agitated - it will become a releasing source for particles and dusts that can cause respiratory irritation or trigger allergies, just as can hard surface flooring when soils are allowed to build up."

Another Viewpoint on Carpet

by Jeffrey C. May, M.A., CIAQP (Certified Indoor Air Quality Professional)

Carpet acts as a dust trap, however, all the dust trapped in a carpet can never be removed by vacuuming, so when carpet is disturbed by activity, particulates are aerosolized.

Dust also accumulates on hard flooring but the surface does not trap the dust, so virtually all of it is readily removed. Therefore disturbing a clean hard surface floor never releases as many particulates as a clean carpet.

I have taken air and dust samples in thousands of structures and when there is activity on carpeting, there is always more aerosol than in spaces with solid flooring.

For the non-CRI-approved vacuum experiments, dust was allowed to settle for 4 minutes at which time the airborne particle levels ranged between 0.4 and 0.8 micrograms/meter3. The vacuum was turned on but kept stationary over a dust-seeded test carpet for 10 minutes. Airborne particle levels increased slowly from 1.0 to 6.3 micrograms/meter3 over the 10 minute period. At this point, the vacuum was mobilized at a rate of 1.8 feet per second. Within ninety seconds, the airborne particle level rose to 463.3 micrograms/meter3. The peak airborne level was reached 30 seconds later at 553.7 micrograms/meter3. (Note: This is 15.6 times the peak level detected with the CRI approved Green Label vacuum tested. See below.) Over the remaining 8 minutes of the experiment, the airborne particle levels declined to a final level of 156.1 micrograms/meter3. The vacuum was turned off and the particle level was tracked for 4 minutes. At the end of this period, the airborne particle level had fallen to a level of 136.0 micrograms/meter3.

For the CRI Green label-approved vacuum experiments, dust was again allowed to settle for 4 minutes, at which time airborne particle levels ranged between 0.6 and 1.1 micrograms/meter3. The vacuum was turned on and kept in a stationary position over a dust-seeded test carpet for 10 minutes. Airborne particle levels increased slowly from 0.9 to 8.7 micrograms/meter3. At this point the vacuum was mobilized at a rate of 1.8 feet per second. At 1 minute of operation a peak particle level of 35.4 micrograms/meter3 was reached. Over the next 90 seconds, this level declined to 26.2 micrograms/meter3. Over the rest of the 10 minute experiment, the airborne particle levels ranged between 25.9 and 21.9 micrograms/meter3. The vacuum was turned off and the particle level was tracked for 4 minutes. At the end of this period, the airborne particle level had fallen to a level of 18.9 micrograms/meter3.

Soiled Carpet Affects Indoor Air Quality

According to Dr. Andrea Ferro, in a 2001 report from Stanford University:

"The air is filled with tiny particles called particulate matter (PM), which has been linked with allergies, asthma, and heart and lung disease. By examining PM that is 'kicked up' or re-suspended by indoor human activity, [we can] find ways to reduce this pollution ... Next to second-hand cigarette smoke and cooking emissions, house dust re-suspended by indoor human activity is the largest source of PM that we breathe.

"... a variety of indoor human activities re-suspend high concentrations of PM between one and 10 um (microns) in diameter within the breathing zone.

"...[Dr. Ferro] set up the filter samplers and real-time instruments in stationary locations outdoors and indoors at a home in Redwood City, California. All instruments were located at breathing height. [Ferro] carried a third identical set of instruments at breathing height while she performed a variety of activities such as dusting, vacuuming, walking, dancing, and folding clothes.

"Using the real-time instruments, [Ferro] found that carpets increased concentrations of PM [significantly] ... over bare floor. Carpets that had not been vacuumed for several weeks increased concentrations by more than two times over carpets that had been vacuumed the previous week. Also, the more vigorous activities re-suspended the highest concentrations of PM. For example, dancing on a carpet increased concentrations more than walking on a carpet. Activities where dust reservoirs were disturbed, such as dry dusting, folding clothes and blankets, and making a bed, released the highest concentrations. Surprisingly, just walking around and sitting on furniture increased concentrations as much as vacuuming."

For the walking experiments, a similar protocol was followed. A hard surface and carpet were seeded with test dust. The test walker stood quietly for 4 minutes, at which time in both hard surface and carpet area cases, the airborne particle levels were steady for the entire period at 0.0 micrograms/meter3.

On the hard surface floor, the test walker then began walking at a rate of 3.8 feet per second for 18 minutes. At 1 minute, the airborne level had risen to 15.1 micrograms/meter3. At 2 minutes, the level was 91.3 micrograms/meter3. The airborne particle levels rose steadily over course of the entire 18 minute walk. The peak concentration was 943.4 micrograms/meter3 reached at 17 minutes. This level is 8.9 times the peak level seen on a carpeted surface.

For the carpet walking experiment, the airborne particle levels were steady for the entire 4 minute settling period at 0.0 micrograms/meter3. When walking began, the particle levels increased to 7.8 micrograms/meter3 at 30 seconds and 14.4 micrograms/meter3 at 1 minute. The rise in particle levels was much more gradual. The peak level of 105.6 micrograms/meter3 was reached at 10 minutes of walking. (Note: this peak level was not exceeded in three replicates of this experiment). The levels then began to decline, so that at the end of the 13 minute walk the airborne particle level was 81 micrograms/meter3.

Source: "Cleaning and Foot Traffic Emissions Analysis"

Asbury, G - Test Number 0072198. Professional Testing Laboratory, Inc., Dalton, GA. Unpublished data. 16 pages. May, 2002.

The Carpet & Rug Institute (CRI)

P.O. Box 2048

Dalton Georgia 30722
carpet-rug.org

(Note: The views expressed in this article are those of the authors, and do not necessarily represent those of The Healthy House Institute, LLC.)

Airborne Dust - Is There More from Carpet or Hard Floors?: Created on February 28th, 2008. Last Modified on February 28th, 2008