A COMPARISON OF INDOOR MICROBES IN TWO OLD FOLKS HOME WITH DIFFERENT VENTILATION SYSTEMS

摘要

An investigation of indoor air microbes of two Hong Kong Old Folks Home, one with naturally ventilation and another with mechanically ventilation device, was carried out. Samples of airborne fungi and bacteria were taken from five indoor sites characterized by different human activities. An outdoor sample was also taken for comparison. Airborne microbes were collected by the Reuter Centrifugal Air Sampler (RCS) for viable sampling and Zefon Air-O-Cell (AOC) for non-viable sampling. Dug-borne fungi were also collected by swabbing surfaces of known surface area. In air samples, the fungal counts collected by AOC were higher (10-128 times) than that of RCS. The dominant fungi found in both Homes were similar. In both Homes,Aspergillus spp. had the highest proportion while the abundance of Penicillium spp. and Cladosporium spp. were similar. In the mechanically ventilated Home, the proportion of Cladosporium spp. in dust-borne fungi was much higher than that of Penicllium spp., and was followed by Aspergillus spp.. However, in the naturally ventilated Home, the highest proportion of dust-borne fungi were Pencillius spp. and Aspergillus spp. while the proportion of Cladosporium spp. was the lowest. Both bacterial counts and fungal counts in air in the naturally ventilated Home were higher than that in the mechanically ventilated Home. The lower relative humidity (RH), 56%-69%, in mechanically ventilated Home was probably responsible for lower fungi counts while a high RH, 72%-85%, in the naturally ventilated Home resulted in higher fungal counts. This study suggests that a mechanical ventilation system contribute to better indoor air quality if it can be properly maintained.