Thermal environmental interference with airborne bacteria and fungi levels in air-conditioned offices

Indoor airborne bacteria and fungi levels can be selected as indicators of a healthy indoor environment. This study investigated the relationships between the airborne bacteria levels, fungi levels, and thermal environmental parameters, i.e., air temperature and relative humidity, in some offices with a Mechanical Ventilation and Air-Conditioning (MVAC) system operating. A total of 101 samples were collected from two typical Hong Kong air-conditioned office premises. There was evidence that the operation of the MVAC system would have significant influence on both of the indoor airborne bacteria and fungi levels. The results showed that no significant difference in airborne bacteria and fungi levels was observed between offices having similar thermal environments (p > 0.05). However, significantly higher airborne bacteria and fungi levels were found in the same office during non-office hours when the air-conditioning system was shut down (p<0.03). It was also reported that the airborne bacteria and fungi levels would be correlated with the thermal environmental parameters in some offices (p<0.0001).