HVAC

Heating Ventilating and Air Conditioning (HVAC) system components operate in warm, dark, humid environments that are ideal breeding grounds for mould and mildew that cause odours and can inhibit system efficiency. At the University of Southampton, Professor Keevil has undertaken work assessing the efficacy of copper as an antifungal surface for air-conditioning systems, as an alternative to aluminium. The results show that on copper, there was increased die off of fungal isolates tested compared to aluminium^[1]. In addition, copper was also shown to prevent the germination of spores present, thereby reducing the risk of their release.

To support the laboratory data, a pilot-scale system was constructed at the University of South Carolina, funded by the US Department of Defense (DoD) under the Telemedicine and Advanced Technology Research Center (TATRC) under the leadership of Dr Mike Schmidt. This programme sought to validate the concept of improved HVAC system performance through copper component use in these systems. The experimental setup compared copper heat exchangers, drip pans and other components to their aluminium counterparts. Additionally, copper and aluminium coupons inserted in between heat exchanger fins were removed periodically to observe biofilm growth.

Dr Schmidt and his team found that commonly-used aluminium components developed stable biofilms of bacteria and fungi within four weeks of operation, whereas the antimicrobial properties of metallic copper were able to limit the bacterial load associated with the copper heat exchanger fins by 99.99% and the fungal load by 99.74% during the same time period.^[2]

The data detailed here support the view of others that, when copper is substituted for aluminium in the construction of heat exchangers, a substantial and significant reduction in the biofilm associated with the heat transfer device found in residential and commercial HVAC systems can be achieved.

Associated improvement in indoor air quality was evaluated in a recently-completed field trial in occupied military barracks at Fort Jackson, South Carolina.  Results showed that the concentration of airborne fungi in the barracks with copper heat exchangers were significantly lower than in the barracks with aluminium heat exchangers.  This suggests that copper HVAC system components can be helpful in reducing occupant exposure to airborne fungi, though more long-term data is needed to fully assess this.

The US Environmental Protection Agency granted a "Treated Article Exemption" registration for copper alloys in HVAC applications in September of 2010.  This registration allows copper HVAC components to make product protection claims by suppressing the growth of bacteria and moulds that reduce system efficiency and cause product deterioration or foul odours.  These claims are supported by EPA registration 82012-7.