Pure copper: Research examines copper's antibacterial effectiveness
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| From left, Liv Haselbach, civil and environmental engineering; Gene Feigley, environmental health sciences; and Jamil Khan, mechanical engineering. All photos: Kim Truett, University Publications |
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Ancient Greeks used copper for purifying drinking water, and early Phoenicians nailed copper to the hulls of sailing vessels to prevent barnacle growth.
Now University researchers are conducting experiments to see if copper components can control disease-causing bacteria in heating, ventilation, and air-conditioning (HVAC) systems. The dark, damp interior of such systems makes them ideal breeding grounds for germs -- and an ideal place to investigate a novel way to control airborne pathogens.
"Condensing coils and drip pans in HVAC systems can harbor bacteria, viruses, and molds," said Gene Feigley, an environmental health sciences professor who is working with colleagues in mechanical engineering and civil and environmental engineering as well as the Medical University of South Carolina.
"A lot of research already points to the ability of copper and copper alloys to eradicate these pathogens on contact. We want to determine if adding copper components to air handling equipment will result in a more germ-free indoor air environment."
Feigley and his co-principal investigators -- Jamil Khan in mechanical engineering and Liv Haselbach in civil and environmental engineering -- are working under a $1 million Congressionally funded contract from the Department of Defense's Telemedicine and Advanced Technologies Research Center. Their research will include testing in Army barracks at Fort Jackson in Columbia and in a laboratory in the Arnold School of Public Health Research Center.
"Conventional HVAC systems use aluminum condensing coils and heat exchange fins and plastic or metal drip pans," Khan said. "Aluminum is durable and has excellent thermal properties, but it has no ability to kill pathogens. In fact, microorganisms can survive on aluminum and stainless steel surfaces for up to a month."
Lab tests have shown that copper and copper alloys can eradicate pathogenic bacteria within 90 minutes at room temperature and within several hours at chilled air temperatures. Copper ions are thought to overwhelm and compromise the integrity of a bacterium's plasma membrane and effectively suffocate the cell or cause irreparable oxidative damage.
To test copper's antimicrobial qualities in HVAC systems, the researchers have ordered custom-built equipment with copper condensing coils, fins, and drip pans and identical systems with conventional aluminum components. The new HVAC systems will be installed in identical wings of a Fort Jackson Army barracks. One wing will be heated and cooled by the system with aluminum components; the other wing will have a copper-component-only system.
"We'll pretest the indoor air quality before putting the new systems in; then we'll test the barracks four or five months later to see which side has better air quality," Khan said.
In another component of the project, small HVAC systems with copper and aluminum components will be tested side by side in a Public Health Research Center laboratory. The researchers will feed precise quantities of dust and bacteria into each system, then check the components and the air in each test chamber for the presence of pathogens.
"If the copper components are effective, this could become part of the green building movement, especially in high-density housing," said Haselbach, who teaches sustainable construction engineering.
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