Research Looks at Copper Heat Exchangers as Air Purifiers

A field trial at Fort Jackson in Columbia, SC is comparing the ability of antimicrobial copper HVAC components with the more commonly used aluminum components in controlling the growth of odor-causing bacteria and fungi in HVAC units.

In addition to mitigating odor, the copper elements are expected to improve system efficiency by reducing organic buildup on heat transfer surfaces.

Components being replaced with copper are those in which microbial contaminants tend to thrive—cooling coils, heat exchange fins and drip pans.

Independent laboratory studies have proven that copper is antimicrobial and can kill many of the pathogens that grow in HVAC units. Cleaner units will provide increased heat transfer, decreased air flow resistance and overall increased system efficiency. Copper HVAC elements are highly recyclable, and copper has the advantage over aluminum in superior thermal conductivity.

The U.S. Department of Defense is funding the research, estimated at about $1 million. In conjunction with the real-world field trial at Ft. Jackson, a controlled laboratory study is taking place at the Arnold School of Public Health of the University of South Carolina, under the care of Dr. Harold Michels, senior vice president of technology and technical services, the Copper Development Association (CDA).

The Ft. Jackson trial — under the care of Dr. Charles Feigley, professor of environmental health sciences at the University of South Carolina — is comparing the ability of antimicrobial copper HVAC components with the more commonly used aluminum components in controlling the growth of odor-causing bacteria and fungi in HVAC units. Components being replaced with copper are those in which microbial contaminants tend to thrive—cooling coils, heat exchange fins and drip pans.

The trial is designed to test the effectiveness of copper surfaces in inhibiting the growth of microbes which are not only the source of foul odors, but can also build up on heat transfer surfaces and compromise the thermal efficiency of the unit. In addition to being antimicrobial, the copper elements are highly recyclable and are better thermal conductors than their aluminum counterparts.

Dr. Feigley, the principal investigator for the study, says the research is needed in part due to the tighter building envelopes in modern construction.

“The results of this real-world trial should encourage advancements in the design of HVAC systems," Feigley says. Copper air conditioning heat exchangers have been installed at two barracks at Fort Jackson, the US. Army’s largest training site. Each barracks has six air conditioning systems. “We installed six copper heat exchangers in one barracks, and six aluminum heat exchangers in another barracks, and we expose them to the same composition of microbes, temperature, and humidity,” Feigley explains.

The accompanying video highlights the installation of one of the heat exchangers at Ft. Jackson. Courtesy CDA and Kellen Company PR.

Feigley is assessing the buildup of bio-films in the heat exchangers over time, and looking at the production of biological aerosols that would have an adverse effect on indoor air quality, and possibly distribute some disease causing organisms.

The copper cooling coils, heat exchange fins and drip pans were manufactured by Luvata, a metal fabrication and component manufacturing company based in Delaware, OH.

In addition to the trials, the Copper Development Association is pursuing U.S. Environmental Protection Agency (EPA) registration of copper alloys for use in protecting HVAC components. For centuries, copper has been known to provide one of the most pure surfaces. Research has found copper can inhibit especially troublesome pathogens, including MRSA (a bacterial infection that is highly resistant to some antibiotics), Clostridium difficile, Escherichia coli (E.coli), Legionella pneumophila (Legionnaire's disease bactera) and Influenza A viruses. Clinical trials examining copper's antimicrobial potential and role in fighting pathogens, transmissions of germs and Influenza A viruses such the bird flu and swine flu epidemics are being conducted in the U.S., United Kingdom, Germany, Japan and South Africa.