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Fall 2007

Naturally Antimicrobial, Copper May Also Improve Air Quality

Healthy HVAC Systems Is Goal of New Research

Research has shown that moisture condensing in air conditioning systems can create an environment where microorganisms thrive. High-efficiency air handling systems (inset) with naturally antimicrobial copper components not only improve vehicle engine output and cooling, they also help to inhibit mold and bacteria growth. Studies are underway to demonstrate the effectiveness of copper systems in commercial air conditioning as well.

High-resolution version of this photo.

Seafarers have known for generations that copper plates and paints prevent algae and barnacles from growing on their boat hulls. Today, the heating, ventilation and air conditioning industry may be learning a similar lesson.

Copper and copper-rich alloys not only repel marine growth, they are also naturally antimicrobial. Bacteria and viruses-germs, in common language-simply can't live for long on copper-based surfaces. As a result, medical researchers and scientists have begun to focus on the germ-fighting ability of these metals.

An area of special interest to these researchers is heating, ventilation and air-conditioning (HVAC) systems, which provide a moist, dark, closed environment that can be a breeding ground for mold, mildew and bacteria.

Many residential and virtually all commercial buildings rely on HVAC systems to heat, cool, ventilate, clean, humidify or dehumidify their indoor air. Passenger cars and public transportation systems have similar "climate control" systems.

Copper-in the form of pipes, tubing, cooling fins and other parts and equipment-has been a critical component of these systems since they were invented. In recent years, however, less-expensive aluminum and plastic components, which have no inherent antimicrobial properties, have replaced many copper HVAC parts. This has raised concerns that the conditioned air we breathe at home, at work and in public spaces could actually be making us sick.


Research by Professor C. William Keevil at the University of Southampton, U.K., has demonstrated that copper alloys are naturally antimicrobial and effective against a wide range of pathogens. Recently, preliminary data from the university also showed that brass surfaces reduce the amount of Aspergillus niger (black mold) found on them by about 99 percent within six hours, while aluminum surfaces have virtually no effect on the organism.

As evidence of copper's antimicrobial effectiveness accumulates, the use of this ancient metal in HVAC systems is being re-examined from a fresh new perspective.

The Department of Defense, through the U.S. Army Medical Research and Materiel Command, recently awarded a congressionally funded contract to study the antimicrobial effects of copper components in HVAC systems. This multiyear research project will be carried out in laboratories, medical facilities and military bases.

One reason for the DoD's keen interest: Last year a certified independent laboratory undertook the most rigorous experimental testing of copper alloys ever attempted, which provided concrete evidence of copper's antimicrobial properties. To verify the results, the International Copper Association (ICA) and the Copper Development Association (CDA) funded an additional series of controlled experiments by a U.S. Environmental Protection Agency-approved test center. The ICA and CDA goal is to gain acceptance from the EPA to make human health claims related to the antimicrobial properties and use of copper alloys.


The verification that copper and brass possess antimicrobial properties is exciting news, but what does it mean to the HVAC industry?

Automotive industry research has shown that moisture condensing on a vehicle's air-conditioner evaporator traps dust and creates an environment where microorganisms thrive. These bacteria and mold form a "slime-layer," or biofilm, that is a focus of investigation by scientists who study the natural ecologies of bacteria.

The researchers have learned that by inhibiting biofilm growth in climate control systems, unpleasant odors can be eliminated. And if copper substrates prevent microbe growth, biofilms can't form. Consequently, using copper alloys in climate control systems could be effective in eliminating not only bad odors, but also the unhealthy atmosphere created by the presence of mold spores and bacteria.


The antimicrobial properties of copper and copper alloys are now firmly established on a foundation of quantified experimental results. However, these extraordinary properties are just beginning to be fully appreciated and applied to the development of products and systems that can control microorganisms in the environment.

The Department of Defense research now underway hopes to demonstrate that harmful bacteria and fungi can be eliminated or effectively reduced by replacing aluminum and steel HVAC components with parts made of copper or copper alloys. These studies are just a first step in clarifying how copper's naturally antimicrobial ability can not only contribute to improved indoor air quality, but also to creating a more healthful human environment in hospitals, homes and public spaces-and anywhere germs thrive. Cu


International Copper Association, CuproBraze Executive Report

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