Scoping indoor airborne fungi in an excellent indoor air quality office building in Hong Kong

This study aims to investigate the differences in indoor airborne fungal exposure between a selective subset of air-conditioned offices within a building classified with excellent indoor air quality (IAQ) in Hong Kong and typical offices in Hong Kong and other countries. Assessments of the indoor and outdoor fungal exposure levels and compositions, and indoor-to-outdoor (I/O) fungi count ratios were conducted in 82 offices of a building with excellent IAQ. The indoor airborne fungi were detected in 97.6% air samples with airborne fungi count (AFC) ranged from 2 to 92 CFU m-3, and with a mean I/O ratio of 0.5. It was reported that the indoor AFC was significantly lower than other typical offices in Hong Kong and other countries. Aspergillus, Cladosporium, Penicillium and yeast were dominant indoors but an outdoor dominant fungi Alternaria was not detected in the offices. This study reveals that better control of thermal conditions and proper maintenance of the air-conditioning system would lower the AFC. In addition, a significantly higher relative abundance (RA) of Aspergillus and lower RA of Cladosporium were also reported. It presents a useful reference for IAQ assessment regarding the quantification of airborne fungal exposure in air-conditioned offices in a building with excellent IAQ. Practical application: An assessment of exposure levels to common indoor airborne fungi, such as Aspergillus, Cladosporium, Penicillium and yeast in Hong Kong air-conditioned offices reveals that an excellent office environment with good thermal and IAQ control would associate with a significantly lower airborne fungi count. A significant different pattern of indoor airborne fungi were observed that a significantly higher relative abundance of Aspergillus and lower relative abundance of Cladosporium were reported.