Indoor air quality in New Zealand office buildings : studies of airborne bacteria and fungi

Abstract

The aim of this thesis was to investigate the levels of indoor airborne bacteria and fungi in fully sealed mechanically ventilated offices in New Zealand. One of the main objectives was to examine the indoor airborne bacterial and fungal levels in Auckland and Wellington offices and to compare the quality of indoor air in offices in both cities. Examining the differences in indoor airborne bacterial and fungal levels between complaint and non-complaint offices as well as comparing those levels with those of similar indoor environments overseas was also one of the main objectives of this thesis. Indoor and outdoor air data used in this thesis were recorded during commercial investigation of 235 offices in Auckland and Wellington by the Institute of Environmental Science and Research (ESR) and Advanced Building Services (ABS). This data included measurements of indoor microclimatic parameters (temperature and relative humidity), indoor and outdoor airborne bacterial and fungal concentrations and indoor carbon dioxide levels. Statistical analyses showed the indoor bacterial levels in Auckland offices were significantly higher than those of Wellington offices. Indoor fungal levels in Auckland offices, on the other hand, were significantly below those of Wellington offices despite the fact that outdoor fungal levels in Auckland were at least three times higher than those of Wellington. No significant differences have been observed between airborne bacterial and fungal levels in complaint and non-complaint offices. Indoor airborne bacterial and fungal levels in New Zealand offices appeared also to be within the levels of those of overseas offices. However, as the bacterial and fungal sampling techniques used by ESR and ABS were different from those used in overseas studies and this can affect airborne bacterial and fungal absolute counts significantly, care is needed in making such comparisons. Finally, an evaluation tool has been developed to overcome the difficulties associated with comparison between indoor airborne fungal levels obtained using different measurements techniques. This tool can be used to establish whether elevated fungal problems exist in an office environment and the likely causes of these problems.