Study On The Airborne Microbial Contaminant In Hospital Wards

In recent years, the matter “IAQ” has been payed more and more attention, the airborne microbial contaminant would be the one of the main indoor contaminants. The airborne microorganisms are in the form of aerosols in the air, them could get into body with the air when human breathes. The aerosols could invade into different human tissues depond on their partical sizes, and do harm to human, besides, some airborne pathogenic microorganisms could cause illness. The dense-occupancy and high-traffic make inpatient building to be a huge concentration of airborne microorganisms. The occupants in wards are usually weak and non-immune, easy to lead to some diseases or get hospital-acquired infected by airborne microorganisms. This paper bases on the National Science Foundation of China(No.51278506), series of field experiments in air-conditioned wards are conducted to study the airborne microbial contaminant, aerosol distributions and dominat aieborne microbial genuses. The results would provide basic data and theoretical support to HVAC design, operation and management in wards.Fistly, the knowlegde about airborne microbial contaminant, aerosol distributions and dominat aieborne microbial genuses of different buildings are obtained by literature research. Based on these knowledge, the suggestions of revising perfectly to current airborne microbial contaminant standards are proposed, and a contamination index is recommended for airborne microbial contaminant evaluation in wards.Then, the field experiments on airborne microbial contaminant are conducted in hospitals, and the samples are cultivated, counted and identified in lab.The summer airborne bacterial concentration in wards is higher than winter, it is contrary to the airborne fungal concentration in wards. In the same season, the airborne bacetiral concentration is higher than airborne fungi. In hospital A there is aiborne microbial contamination in winter, and airborne bacterial conctaminnation in summer. In hospital B, airborne microbial contamination exists both summer and winter. Combined the existed concludes and results of the analyses of airborne microbial concentrations in wards, the seasons, temperature and RH are determined as common influence factors of airborne microbial concentration, and the occupant population could affect the airborne bacterial concentration.The winter and summer distribution characteristics of airborne microbial aerosols are obtained. The airborne bacterial aerosols are mainly lager than 3μm in winter and between 1~6μm in summer; the distributions of airborne fungal aerosols are almost the same in winter and summer, they are mainly from 1μm to 3μm. The airborne bacterial aerosol median diameters are less than 5μm, and the airborne fungal aerosol median diameters are less than 3μm. The seasons could only affect the airborne bacterial aerosol median diameters.Most airborne bacteria are identified Gram-positive bacteria by microscopy, so the Gram-positive bacteria are the main compositions of airborne bacterial contaminant. The dominant fungal genera identified are Aspergillus spp, Penicillium spp, Alternaria spp and Cladosporium spp, both in winter and summer.