Copper prevents growth of bacteria in HVAC systems

Dr Michael Schmidt, professor and vice chairman of microbiology and immunology at the Medical University of South Carolina, and his team have published a new study evaluating the efficacy of copper in reducing contamination in Heating Ventilation and Air Conditioning (HVAC) systems.

In relation to this, Cleanroom Technology has an interesting feature about the use of copper in HVAC systems as a microbial reduction measure. The conditions in many HVAC systems would appear to be ideal environments for the growth and propagation of microorganisms.

The researchers conducted a comparative study where heat exchangers fabricated from either antimicrobial copper or aluminium were evaluated for their ability to limit microbial growth, using a full-scale HVAC system under conditions of normal flow rates using single-pass outside air.

It was 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. Contaminants accumulate on heat exchanger coils and fins, in condensate drain pans, on air filters, and in air ducts. Indoor surfaces and building occupants can then be exposed to bio-aerosols from these sites.

To test the impact of copper surfaces, chilled water was circulated through the experimental heat exchangers. After a week the system was temporarily stopped and 99 coupons of either copper or aluminium were installed into four equivalent copper and aluminium heat exchangers. Triplicate sets of coupons were then removed from each exchanger four weeks after their installation.

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

The paper was published in the journal Current Microbiology

Posted by Tim Sandle