A series of bioaerosol measurements have been conducted at two typical oces in Hong Kong for both a 4-day and a weekly
period. Both the investigated oces were installed with heating ventilation and air-conditioning (HVAC) 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 pro®le of bioaerosol inside oce
environments during oce hours, and to determine the eects of air change rate on the concentration pro®le. 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 oce environment had less signi®cant eects than ®ltration 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. 7 2000
Elsevier Science Ltd. All rights reserved.