For Shanghai residents, public buses are the primary method of transportation. The urban population spends around 8% of each day travelling by bus, which equates to around one and a half hours daily. In order to protect the health of these passengers, copper fin air conditioners have been deployed on the buses to rapidly and completely kill bacteria, viruses and fungi that can thrive on non-copper fins and circulate around the system.
Air quality aboard buses is a concern since airborne pathogens can be passed between passengers, contributing to outbreaks of disease. Copper and many of it alloys such as brasses and bronzes (collectively termed ‘antimicrobial copper’) have been proven to eliminate disease-causing pathogens on contact, which has led to their installation in hospitals, schools and transport hubs worldwide. They are currently deployed in the form of frequently-touched surfaces – such as door handles, hand rails, taps and light switches – and research into antimicrobial copper’s efficacy in heating, ventilating and air conditioning systems has led to growing interest in the HVAC field.
Shanghai is leading the way with the deployment of antimicrobial copper HVAC systems on its buses, which have replaced commonly-used aluminiumfins, that do not exert an antimicrobial effect. Due to its antimicrobial properties, copper fins can eliminate bacterial, fungal and viral growths that commonly build up in systems, meaning their surface is cleaner for longer, offering a greatly expanded service life and contributing to improved air quality.
Exploring the potential of these systems, the Shanghai Municipal Center for Disease Control and Prevention (SCDC) undertook testing between 2010 and 2012. Buses operating in similar conditions (e.g. time and location) were fitted with either copper or aluminium fins and radiators, and the level of contamination on each was monitored.
They found that microbial levels on the copper surfaces were significantly lower than those on the aluminium, which concurs with a recently-published US study investigating the same subject in a laboratory environment.
Dr Michael Schmidt - Professor and Vice Chairman of Microbiology and Immunology at the Medical University of South Carolina - and his team have published a study evaluating the efficacy of antimicrobial copper in reducing microbial contamination in heating, ventilation and air conditioning (HVAC) systems.1
They 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.
They 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.
The results indicate a role for antimicrobial copper in reducing contamination on heat exchanger surfaces, which could potentially improve resultant air quality, and increase efficiency in HVAC systems. The SCDC’s research into the Shanghai bus installations supports these results.
The Chinese and American studies are timely, given the recent publication of a research article from the Robert Koch Insitute in Berlin: ‘Quantitative assessment of passenger flows in Europe and its implications for tracing contacts of infectious passengers’.2
This noted that researchers from REACT3 – a European infectious disease research programme – had concluded that “environmental parameters do have an effect in the risk of transmission of infectious disease from one passenger to another in public ground transport. While the duration of exposure and proximity to other passengers are seen as important parameters in assessing the risk of disease transmission, little is known about the influence of technical parameters such as ventilation systems in ground conveyances on transmission.” The new studies are a beginning to addressing this lack of data.
1 Characterization and Control of the Microbial Community Affiliated with Copper or Aluminum Heat Exchangers of HVAC Systems, Schmidt et al. 2012
2Quantitative assessment of passenger flows in Europe and its implications for tracing contacts of infectious passengers, M Askar et al. 2012
3 Response to Emerging infectious diseases: Assessment and development of Core capacities and Tools
Published by ICA, http://www.antimicrobialcopper.com