coppertalk

By Charles Feigley, Ph.D., Professor of Environmental Sciences at the University of South Carolina

Charles Feigley, Ph.D., Professor of Environmental Health Sciences at the University of South Carolina, this month presented a paper at the 12^th International Conference on Indoor Air Quality and Climate in Austin, Texas. The paper described studies underway at the Fort Jackson U.S. Army base in Columbia, S.C on the use of copper heat exchangers to suppress the growth of bacteria, mold, and mildew that can cause odors and compromise system effectiveness. This study is supported by the U.S. Army and is a collaboration of the Copper Development Association, the University of South Carolina, the Medical University of South Carolina and Washington State University.

Many studies have shown a relationship between poor indoor air quality and heating, ventilation and air conditioning (HVAC) systems. The U.S. Army is interested because respiratory infections cause a quarter of military personnel hospitalizations and these can significantly interfere with military training and troop readiness.

The research team replaced all the heat exchangers in two nearly identical three-story Army barracks. In one barracks, we installed these six new copper heat exchangers.

We’ve been working on a study, supported by the U.S. Army Medical Research Command, to look at the potential benefits of copper HVAC heat exchangers instead of the standard aluminum exchangers. We retrofitted the HVAC system in a barracks at the Fort Jackson U.S. Army base in Columbia, S.C. with copper components in places where contaminants tend to thrive – chilled water tubes, heat exchange fins and drip pans. The trial was designed to test the effectiveness of copper surfaces in inhibiting the growth of microbes. These microbes can emit foul odors and build up on heat transfer surfaces to compromise the thermal efficiency of the units. Copper is an intrinsically antimicrobial engineering material.  It’s also more thermally conductive than either stainless steel or aluminum, the materials frequently used for HVAC system components.

We conducted the study in the barracks during the cooling season (April 19 through September 22, 2010) and had done a similar study earlier during the winter months. We also performed a complementary study in our lab. We took samples of metal strips inserted into the heat exchanges and from air leaving the systems, looking for both bacteria and fungi. We were pleased with the results. The barracks with copper systems had significantly lower levels of microbes in the air*. In lab experiments, we found hundreds to thousands of times less microbial growth on copper surfaces than on aluminum.

Using copper components in HVAC systems would provide benefits in a number of locations – from barracks to hospitals to other public spaces. It could possibly help eliminate moldy smells and sick building syndrome, and potentially increase system energy efficiency. Additional research is needed to clarify copper’s impact in occupied spaces and to explore its effect at higher microbial levels. For more information on this, please email me at, cfeigle@mailbox.sc.edu.

*Results of this study have not been reviewed by the U.S. Environmental Protection Agency.