Fundamental Science Concepts in Effective Cleaning

What is environmental science?

Environmental science unites all the sciences that evolved over centuries. Its origins are in natural philosophy or logically and systematically examining the natural and man-made worlds. This long-term examination produced fundamental concepts for decision-making regarding how we live in relation to natural processes. Cleaning creates a desirable environmental so it is viewed as a branch of environmental science.


How are ecosystems and habitats related?

Man’s habitat is a sub-compartment of the natural environment. Scientific concepts explaining how natural environment processes function are germane to the built human habitat. The natural environment system is represented as interconnected compartments that include the lithosphere, atmosphere, hydrosphere and biosphere.


The lithosphere is comprised of land, sediments and rocks. The atmosphere is a mixture of gases, largely oxygen and nitrogen, held to earth by gravity. The hydrosphere is the watery gaseous envelope surrounding the earth and the liquid water reservoir on and in its surface. The biosphere is the planet’s living and dead organic components. These, along with their sub-compartments, intersect and interact with each other. One of these sub-compartments is the built environment or the human habitat.


Ecology and environmental systems understand how natural systems function. The prefix “eco” comes from the Greek word meaning “home.” Taken literally, ecology means the study of homes. Earth, with its many sub-compartments, is home to all life forms. Our immediate environment—our home—also is considered an ecosystem. Similar environmental management and science concepts and principles as sub-compartments of other natural systems govern the built habitat.

Habitats are where particular organisms live and grow. How that organism interacts with its habitat is its niche. A niche is the set of conditions supporting an organism’s life to make a healthy habitat possible.

Living and non-living components interact in life supporting environments. Living components are referred to as biotic; non-living components are called abiotic. Abiotic components include nutrients, soil, temperature, water, air and sunlight. An ecosystem is created when communities of organisms interact with one another and their non-living chemical and physical environments in a balanced way to sustain life. Every organism must adapt to biotic and abiotic conditions to live in that space.

Changing even one factor breaks down the life support system. When a habitat’s life sustaining conditions are expended or significantly altered, the resident organisms are severely stressed. They become dormant, die or find another home. An ecosystem’s life supporting conditions are found within an optimal range. Exceeding that range places the species in an unhealthy state. The species die if stressed too much. Cleaning or managing unwanted matter reduces stress. 

Many organisms confronted while cleaning are decomposers. They return and move carbon through its natural cycle. This helps us manage more effectively. For example, sub-compartments composed of wet organic matter support fungi or bacteria more readily than others. These living organisms require food and water, making it likely to find mold on wet paper rather than on a clean glass window. This living form of unwanted matter can be controlled by altering its environment, such as removing (cleaning) the water or organic (carbon-based) food supply.


Is there a connection between clean habitat and health?

Man is distinguished from other species by his ability to become free of natural extremes and insulated from the environment that otherwise controls all living things. We sustain life by freeing ourselves from the adverse effects of the natural environment by the habitats we build, maintain and clean.


The built environment is man’s primary habitat and the environment we are exposed to for over 90 percent of our lives.[1] This environment most influences our quality of life and our health. It also is the environment we have the most control over, primarily through cleaning.


Buildings are man-made barriers separating indoors from outdoors. The major difference between these two environments is that the outdoor changing cycles are uncontrollable. A building’s primary purpose is to control the quality of what goes on inside.


Health is “a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.”[2] An elevated sense of well-being is the basis for the healthy human condition. Cleaning creates that condition of physical and mental well-being. A healthy indoor environment provides security, comfort, social interaction and productivity.


Without cleaning there is no hygiene and individuals only can survive in their habitats for so long. Hygiene prevents disease and infection through cleaning. Good hygiene is absent of soil or harmful bacteria levels, microorganisms and harmful matter and is indicated by a state of cleanliness. Effective and high performance cleaning frequently aids in preventing disease and isolation. That is why in the midst of an epidemic good personal hygiene and effective cleaning processes reduce infection.


What makes a building “healthy?”

A building’s healthy state depends on how it looks and feels. Generally, this is determined by how well it is cleaned. Cleaning cannot be separated from healthy building design. Buildings that are not designed and constructed for easy and effective cleaning eventually deteriorate to an oppressive state rather than one that enhances the quality of life.


Essential design elements for healthy indoor environments must address various conditions, which depend—to some extent—on effective cleaning.

  • Usable space that promotes social interaction and productivity;
  • Physical safety and security;
  • Aesthetics or a beautiful view;
  • Physical comfort (ergonomics);
  • Lighting that includes managing glare or light reflectance;
  • Acoustics and managing annoying noise;
  • Climate control to keep the surroundings and dry; and
  • Maintaining a sanitary environment.

What are the basic laws of science?

There are two fundamental laws of matter and energy.

  1. Matter and energy are not destroyed but rather they remain constant. Matter and energy circulate or matter turns to energy and energy turns to matter.
  2. All organized systems seek their most disorganized state. Also known as entropy, this explains man’s constant need for effective cleaning.

Entropy measures the extent of a system’s disorder. More activity equals more entropy. The more objects and activities in a space, the greater the complexity and disorder. This also is called the law of requisite variety. If no activity or elements are present in an environment there is no disorder. When only one activity or element is present there is no interaction or disorder. When several activities go on simultaneously interactions occur and disorder is created. More than 50 activities happening in the same environment creates high disorder, which is multiplied well beyond direct proportion as the number of events and activities increase.


As a space increases in complexity and disorder so does the need for cleaning. The amount of unwanted matter accumulating in an environment mainly is a function of its activity level and compartment size. The more movement in a space the more unwanted matter is generated and the more cleaning and maintenance is required.


The need for an orderly environment becomes evident daily, especially as populations increase in the built environment. A city of 20,000 people requires less sanitary infrastructure than one with 500,000 people. A home to a family of four requires more cleaning than one for a family of two. An office of 500 workers needs more attention than one with 20. Schools need more regular cleaning during the school year than over the summer. Gyms need less attention on practice days than game days. Accepting the theoretical basis for order and disorder allows us to recognize that a healthy indoor environment depends on a management strategy that incorporates effective cleaning, maintenance and restoration.


Effectively cleaning a defined space with a known activity level and an intended use requires enough energy to move matter. Sufficient energy in cleaning is indicated by money, labor and technology. Effectual cleaning requires more than simply allocating resources and time. Consideration also must be given to the activity level, the environment’s intended use and its need for a specific sanitation level.


Sufficient time also is critical in cleaning. Cleaning removes pollutants from an object or environment and puts them in their proper place. After being identified and located, the pollutants are broken down chemically or mechanically, after which they are contained on a surface or suspended in air or fluid. The surface or fluid then is removed and the contaminant is disposed. Cleaning only can be fully effective if enough time is allocated to each step for proper execution.


What are connected compartments?

Effective cleaning emphasizes the concept of “connectedness.” It examines matter and energy flowing in and between an environmental system’s compartments. It also identifies and studies the life-affecting processes these flows create. Particular attention is given to the effect man has on these natural processes and the influences they have on our well-being.


Cleaning is applied to an environment or an environmental sub-compartment, which contains matter and energy. Objects in the built environment are sub-compartments of that environment and the natural environment. Major sub-compartments of the indoor environment include flooring; the atmosphere; elevated surfaces, such as walls, shelves, furniture and ceilings; and heating, ventilating and air conditioning systems (HVAC). Objects or places within these sub-compartments also are sub-compartments.


Specifying and understanding an environment forces us to recognize its natural tendencies so unwanted matter can be removed or repositioned effectively. How effective each compartment is cleaned determines if their intended purpose is achieved or is unintended environmental conditions or hazards are created. Depending on the compartment matter load and environmental conditions, such as convection and natural ventilation, unwanted matter is continuously transferred among compartments.


What is quantifying matter?

Loading is the quantity of matter or energy introduced or discharged into a system or compartment. Often referred to as organic, dust or gas loading, they are described by units. A unit is a measuring rod that characterizes a particulate measurement. The standard unit of grams describes an amount of matter. Quantity is the actual number obtained with the measuring rod. One gram of matter equals one cubic centimeter, or roughly a thimble of water. A microgram is one-millionth of a gram.


Quantification is essential for assessing cleaning’s effectiveness. Carpet with dusts exceeding two grams per square meter is, on average, unsanitary. Conversely, dusts in the range of 10 micrograms per cubic meter of air suggest a relatively clean environment.


Is there a difference between open and closed systems?

Cleaning is necessary for matter to remain at a sanitary level in closed built environments. In an open environment, matter or energy may be lost or gained, often by moving between the system’s inner and outer sides or from creation or destruction processes within the system. In a closed environment, however, matter and energy are kept within the system where they move between compartments. As closed systems, built environments tend to conserve energy. Matter tends to accumulate and reach a steady-state condition. How much matter depends on surrounding emitting sources and human activity levels.


What is transfer?

Transfer is the movement of matter and energy between compartments. Every environment and sub-compartment retains and transfers matter differently. Before unwanted matter can be moved effectively, there must be a basic understanding of the characteristics of environment and sub-compartments being cleaned. For example, in the presence of air currents, a hard surface holds fewer particles less strongly than fabric surfaces. When air flow through vacuuming moves particles less energy is required from hard surfaces than from fabrics for any quantity of particle mass.


Matter transfers from an environmental compartment (carpet, shelves, indoor air) with or without depending on the amount of substance in the compartment upon transfer. A zeroeth order transfer is when the amount of substance leaving the compartment is independent of the amount of material in the compartment at the time of transfer.


In contrast, the first order matter transfer is when the amount of substance leaving a compartment at a specific time is proportionate to the amount of the substance present at transfer. The first order transfer is useful for describing matter deposition into a compartment from indoor air.


What is the difference between positive and negative feedback?


Positive feedback escalates a system’s change. Negative feedback brings the system to its original state. When a system reaches equilibrium, the matter in each compartment stabilizes. It no longer changes over time because the rate in and the rate out are equal. For steady state, the rate of matter in plus the rate of creating matter inside the compartment equals the rate out plus the rate of destruction within the compartment. Any amount of scheduled cleaning produces a steady state condition indoors.

Michael D. Berry, Ph.D., was chairman of the Science Advisory Council for the Cleaning Industry Research Institute (CIRI) in 2006. The information contained in this article was extracted from Dr. Berry’s papers and presentations at CIRI’s 2007 Cleaning Science Conference and Symposium. To learn more about CIRI visit

Published with permission by the Cleaning Industry Research Institute © 2008.


[1] National Research Council (1986). Indoor Pollutants. Washington, D.C.: National Academies Press.
[2] World Health Organization (WHO) (1990). Basic Documents: 38th ed. (p.1). Geneva, Switzerland.

Michael A. Berry, PhD serves on the Science Advisory Council of the Cleaning Industry Research Institute (CIRI).


Dr. Michael A. Berry retired from the US Environmental Protection Agency in 1998 after a 28 year career with that agency. In EPA he was a senior manager and scientist. He was the Deputy Director of National Center for Environmental Assessment at Research Triangle Park, NC for 22 years. During his EPA career, he had extensive interactions with private industry, trade associations, environmental organizations, governments, the federal courts, US Congress, universities world-wide, and institutions such as the National Academy of Sciences, the World Health Organization, and the North Atlantic Treaty Organization. Dr Berry is recognized internationally as an expert in the subject of indoor environmental quality. Between 1985 and 1994, he directed EPA's indoor air research program.

Since his retirement from EPA he has been a Research Professor at the University of North Carolina at Chapel Hill where he taught several course and wrote numerous articles related to business and environment, built environments, and environmental science and management. He serves as a consultant to businesses and public institutions in the evaluation of environmental management strategies and policy. He directs research on the performance of products and services related to indoor environmental quality. Currently his research focus is the area of cleaning science and indoor environmental management programs for schools and universities.

Dr. Berry served as an Army Officer in Viet Nam 1967-68. He earned a Doctor of Philosophy in Public Health from the University of North Carolina at Chapel Hill, and a Master of Science in Management from Duke University's Fuqua School of Business. He holds both Bachelor and Master of Science degrees in Mathematics from Gonzaga University.