This study characterized the indoor environment of a multi-floor, multi-use, non-problem, non-complaint building through long term sampling for a variety of substances. Sampling was done for biological, chemical, and particulate pollutants. The study further assessed the effects of cleaning on indoor air quality. The study protocol included five months of "baseline" environmental measurements, a rigorous cleaning of the entire building, and subsequently, seven months of environmental monitoring after implementation of an economically-feasible, standard cleaning program.

Air, surface, and dust data from monitoring prior to the cleaning program were compared with those obtained while the improved housekeeping program was in place to assess the effectiveness of the cleaning program on the indoor environment. Correlations between pollutants and other environmental factors were also presented. This work involved a collaborative effort by the Research Triangle Institute, the US Environmental Protection Agency's Environmental Criteria and Assessment Office, the University of North Carolina at Chapel Hill (UNC), the building service contractor, and commercial cleaning and carpet industries, and their suppliers.

The study concluded that an organized cleaning program based upon environmental management principles and fundamental environmental protection guidelines contributed to improved indoor air quality through reduction of total suspended particles, total volatile organic compounds and culturable bacteria and fungi.

Major Findings

Particle Results

• Airborne dust mass, measured as total suspended particles (TSP), provided the most meaningful particle data and showed a statistically significant reduction with improved cleaning.
• Immediately after deep cleaning, carpet dust mass was reduced, particularly on floors with the highest dust loads.
• Soon after deep cleaning, carpet dust mass loads quickly returned to before cleaning levels, confirming carpet as a sink or collector of particles.
• Airborne dust mass was decreased after deep cleaning and continued lower even though the total mass from dust in carpets soon returned to original levels.

Bio-pollutant Results: Correlations

• Airborne levels of bio-pollutants correlated with airborne dust mass, and the bacteria correlation was statistically significant.
• Levels of bacteria and fungi from non-floor surfaces correlated (statistically significant) with airborne levels of bacteria and fungi providing evidence that surface pollutants can be reflective of airborne levels and airborne levels can be reflective of surface contamination.
• Levels of carpet dust bacteria had a statistically significant correlation with airborne bacteria indicating a relationship between the two that demonstrates the need for cleaning pollutant removal as an environmental management tool for maintaining acceptable air quality.

Bio-pollutant Results of Data Comparison

A year-long study of a non-problem building showed that attention to improved housekeeping (in conjunction with proper HVAC operation and maintenance), resulted in sustained reduction of mean levels of:

• airborne bacteria (40%) and fungi (61 %), (Andersen sampler)
• non-floor surface bacteria (29%) and fungi (25%)
• carpet dust bacteria (84%), fungi (93%), and endotoxin (72%).

Deep cleaning resulted in reduction of mean levels of:

• airborne bacteria (58%) and fungi (25%), (Andersen sampler) - non-floor surface bacteria (58%) and fungi (15%)
• carpet dust bacteria (76%), fungi (99%), and endotoxin (98%).

Overall Results

• An organized cleaning program based upon environmental management principles and fundamental environmental protection guidelines contributed to indoor air quality through the reduction of total suspended particles (TSP), total volatile organic compounds (TVOCs) and culturable bacteria and fungi.
• While airborne pollutants increased during deep cleaning, they never reached levels of concern to the researchers, and were shown to decrease rapidly to levels well below the "pre- cleaning" concentrations.
• The study data suggests the ambient, environmental pollution can be significantly controlled through an effective and managed indoor cleaning program.
• Routine, non-floor, surface bacterial and fungal sampling can help identify areas for focused cleaning, as well as provide a useful assessment of a building's changing microbial ecology.

(Pages v-x in study)

Cole, E.C., D. L. Franke, K. E. Leese, P.D. Dulaney, K. K. Foarde, D. A. Green, R. M. Hall, and M Berry. Indoor Environment Characterization of a non-problem building: Assessment of Cleaning Effectiveness. Research Triangle Report Number 94U-4479-014, Research Triangle Institute, Research Triangle, North Carolina. 202 pages. March, 1994.


Historic Study - Characterization of a Non-problem Building: Assessment of Cleaning Effectiveness:  Created on January 26th, 2010.  Last Modified on January 26th, 2010


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Lynn Krafft · 9 years ago

If daily cleaning is described as, "I whacked the dusty shelf with a rag..." and deep cleaning is described as "I removed the dust from the shelf with a treated dust cloth...", the reason for the dramatic reduction in airborne substances is obvious. Could it be that deep cleaning, is simply cleaning that is actually done specifically to remove contaminants rather than move them into the air or rearrange them on the surface? In other words, true cleaning?

The involvement of the HVAC system is also noteworthy. Indoor air and surface pollution is seldom caused by people shaking themselves vigorously when entering a room. The whole environmental control system is involved and the custodians (especially in contract situations) have little control of that. All of us have witnessed heavy dust depositing overnight on surfaces we know were fully dusted the night before.

Even with the initial levels of pollution high enough to merit measurable reduction, the building had no health related problems, indicating that hygienic cleaning is not a necessity in all environments to protect human health. That is not to minimize the value of daily competent cleaning, but it does help balance the value/cost equation.

The conclusion must be that any cleaning program should be designed to be effective and that, when it is, with significant sustained pollutant reduction (dust primarily), the microbial threat real or imagined is reduced as well.

The days of dumping the litter baskets and running a vac down the middle of the hallway and calling that custodial work are over.

January 27th, 2010 | 8:33am Reply
Allen Rathey · 9 years ago

Dr. Gene Cole is one of the original authors. You may contact him at

January 27th, 2010 | 8:17am Reply
Marion Stecklow · 9 years ago

The results of this study are very exciting. Is it possible to view the actual data?

January 27th, 2010 | 8:06am Reply Account Registration

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