Characteristics of bioaerosol profile in office buildings in Hong Kong.

A series of bioaerosol measurements have been conducted at two typical offices in Hong Kong for both a 4-day and a weekly period. Both the investigated offices were installed with heating ventilation and air-conditioning (HV AC) systems coupling with air handling units and fan coil units. Measurements were performed starting from early morning by the Anderson N6 impactor. The primary objectives of these measurements were to determine the temporal concentration profile of bioaerosol inside office environments during office hours, and to determine the effects of air change rate on the concentration profile. The highest bacteria concentrations were recorded to be 2912 CFU/m3 at the early morning hours during the starting-up period of HVAC systems. The highest fungi concentrations were recorded to be 3852 CFU/m3 during the weekend mornings. The results of studies also revealed that the air change rate inside the office environment had less significant effects than filtration on airborne bioaerosols. The background fungi concentration was found to have strong correlation with the indoor relative humidity level provided that the relative humidity level could be maintained for a certain period of time. Of the sampled bacteria 80% were found to be gram positive, while the dominating genera of fungi was found to be Cladosporium and Penicillium.