The airborne microbes of two groups of hospital wards (one equipped with central air conditioning, ACW; the other was naturally ventilated, NVW) were measured simultaneously for two months. The results indicated that during air-conditioning the airborne microbial contamination in ACW was more serious than that in NVW: the average bacterial concentration of ACW (535 CFU/m3) was about 1.2-fold greater than that of NVW (438 CFU/m3), and the average fungal concentration in ACW (174 CFU/m3) was about 1.5-fold greater than that of NCW (113 CFU/m3). O...
