Field And Analysis For Microbial Contamination And Characteristics Of Ventilated Systems In Air Conditioning

Centralized air conditioning systems like people's artery vascular.If having unreasonable design,improper operation and management,the system was considered to be a contributing factor to indoor air pollution,it will diffuse quickly,which directly done harm to their health and life safety in building.Outburst of SARS of 2003, microbial contamination of ventilated systems in air conditioning of public building been a focus of attention.In recent years,domestic and foreign experts and scholars had been carried out many of theoretical analysis and numerical simulation study about the indoor and outdoor microbiological aerosol but there was very little research on microbial characteristic distribution of ventilated systems in air conditioning.A series of field and laboratory tests have been conducted at a typical central air-conditioning system of public building in Xi'an,Shaanxi throughout summer (Jul～Sep,2008) to investigate the characteristics of dust and associated with microorganism and settling microorganisms in the air.And questionnaires were taken by maintenance men to investigate the operation and maintenance rule of the HVAC systems and cleaning periods of the filters and HVAC ducts.The paper survey deeply the status of dust and associated with microorganism of HVAC ducts and air-handling unit,found that there were dust accumulation in different degree in HVAC system and its components,such as:air filter,humidifier, surface air cooler,air-handling unit and so on.The highest dust accumulation weight of duct was 22.30g/m~2.By laboratory examinations,showed that there was fungi growth inside HVAC system.Airborne microorganisms' concentration:air-return segment＞air-supply segment＞filter segment.The serious pollution occurred in the return air section,the highest bacteria concentration was 11638.00cfu/m~3,while the highest fungi concentration was 17614.20cfu/m~3.With the increased of dust weight,the microbiological concentration obviously increased.From microbiological analysis,the dominant bacteria was cocci,the dominating genera of fungi were Cladosporium, Penicillium,Aspergillus.Compared with winner(Nov～Dec,2007),as far as settling microorganisms in the air,bacteria concentration were higher in winter than in summer,but fungi concentration were lower in winter than in summer.For dust and associated with microorganism,bacteria and fungi concentration were much higher in winter than in summer.The result of microbiological analysis had no remarkable change in summer and winner.A series of settling microorganisms measurements have been conducted at air-conditioned room of the building.It showed that in the first 1-2 hour after the HVAC systems start time,the bacteria and fungi levels were higher,and the bioaerosol concentration would be diminished gradually during office hours.Indoor occupants exposed to high levels of microbial contamination,and fungi concentration distribution of the room was uniform.Indoor occupants received the same level of fungi contamination in any place of the room.According to field survey and laboratory examinations,this paper proposed some advices about controlling microbial contamination of ventilated systems in air conditioning.