Study on the Behavior and Control of Microbial Contamination in an Air-conditioning System

大多数所谓的建筑相关疾病都与空调系统中的微生物污染有关。众所周知，空调系统中的污染源对室内空气污染尤其是微生物污染有很大的影响。由于空调系统内部的温度和湿度适合微生物的生长，维护不当会使空调系统成为室内空气的污染源，本研究的目的是弄清空调系统中微生物污染的实际状况，并从建筑卫生学的角度建立控制方法。从2003年4月31日至2006年3月31日，进行了一项关于空调系统维护、原位实验和实验室研究的全国范围的问卷调查。主要研究结果如下：（1）通过对某空调维修单位进行问卷调查， ...更多信息 空调系统，已经澄清，几乎空调系统，包括空气过滤器，热交换盘管，加湿器，风管没有定期清洗。(2)By通过对Alternarialternate、Eurotiumherbariorum、Aspergilluspenicillioides作为生物传感器的生长速度的测定，明确表明盘管下游的环境在70-95%的最低相对湿度下是微生物生长的有利环境。(3)On控制方法（1）控制湿度环境的方法可以抑制微生物的生长速度。（2）在东京的三台空调机组和一台箱式空调机的真实的运行工况下，对中低效空气过滤器对悬浮颗粒物和空气微生物的过滤效率进行了现场试验，结果表明，空气微生物和分布的悬浮颗粒物的过滤效率存在显著的相关性。对空气中的金黄色葡萄球菌、细菌和真菌孢子的过滤效率分别几乎等于对直径大于1 μm、2 μm和5 μm的悬浮颗粒物的过滤效率。这一结果表明，它是可能的，设计室内空气洁净度的生物气溶胶通过使用的空气过滤器的过滤效率分布的悬浮颗粒，而不是空气中的微生物，如细菌和真菌孢子在办公楼。（3）根据2005年夏季实际运行条件下空气过滤器对空气微生物的过滤效率，（重量法预滤74%;对细菌和真菌的去除率分别为87±4.9%（空气处理机组）、96±2.5%（空气处理机组）和90±8.8%（空气处理机组）、97±2.7%（空气处理机组）。此外，由于在空气过滤器的上游和下游都测得了相同的微生物，例如枝孢菌属和青霉属，因此可以认为，相同的空气微生物在室内空气中可能根据空气动力学直径而表现出不同的行为。（4）虽然通过离子发生器的操作，空气正离子和空气负离子的浓度分别升高到2.3倍和1.9倍，但空气微生物的浓度没有降低。（5）酶滤池与对照滤池的粘附细菌和真菌数量无显著差异。（6）空调系统的维护，如定期清洗盘管、加湿器和风道，对于减少空调系统微生物引起的空气污染是最重要的。少

Most so-called building related illness are related to the microbial contamination in an air conditioning system. It is well known that indoor air pollution especially caused by microorganism is strongly influenced by the contaminant source in an air conditioning system. Since the temperature and humidity inside of an air-conditioning system are suitable for growth of microorganism, poor maintenance will causes an air conditioning system to a pollution source of indoor air.The goal of this study is to clarify the actual status of microbial contamination in an air conditioning system, and to establish a control method from the standpoint of architectural hygiene. A national scale questionnaire on maintenance of an air conditioning system, in situ experiments, and laboratory studies were conducted from April 31, 2003 to March 31, 2006. The main results are shown as follows.Actual status of microbial contamination(1)By the results obtained from the questionnaire on maintenance of an air c … More onditioning system, it has been clarified that almost air conditioning systems, include air filter, heat exchange coil, humidifier, air duct are not cleaned periodically.(2)By measurement of the growth speed of Alternari alternate, Eurotium herbariorum, Aspergillus penicillioides which used as a biosensor in this study, it is shown clearly that the environment down stream of a coil is favorable environment for the microbes of the 70-95% of the minimum relative humidity for growing.(3)On some object surfaces of an air filter, a coil, and a humidifier, when many, 10,000 microbes per square centimeter were measured out.Control method(1)It was proved that the method of controlling humidity environment can suppress the microbial growth speed.(2)The results obtained from the in situ experiments about the filtration efficiency of low- and medium- efficiency particulate air filter over both suspended particles and airborne microbes under real operating conditions of three air-handling units and one package air-conditioner located in Tokyo, show that there are significant correlations of filtration efficiency between airborne microbes and distributed suspended particles. Each of the filtration efficiency over airborne staphylococcus aureus, bacteria, and fungal spores is almost equal to the filtration efficiency over suspended particulates larger than 1 μm, 2 μm, and 5 μm in diameter, respectively. This result indicates that it is possible to design indoor air cleanliness on bio-aerosol by using the filtration efficiency of the air filter over distributed suspended particles instead of airborne microbes such as bacteria and fungal spores in office buildings.(3)Based on the results about the filtration efficiency over airborne microbes under actual operating conditions throughout summer season in 2005, it has been clarified that the filtration efficiency of the air filters (pre-filter 74% with weight method ; main filter 65% with dust spot method) over bacteria and fungi were 87±4.9% (AHU), 96±2.5% (OAHU) and 90±8.8% (AHU), 97±2.7% (OAHU), respectively. Furthermore, as the fact that the same sp.of microbes such as Cladosporium sp.and Penicillum sp.were measured out both of upstream and downstream of the air filters, it can be suggested that the same sp.of airborne microbe may show the different behavior according to aerodynamic diameter in indoor air.(4)Although the concentration of positive air ion and negative air ion raised up to 2.3 times and 1.9 times, respectively, by the operation of the ion generator, there was no reduction of the concentration in airborne microorganisms.(5)There were no remarkable differences in the number of adhesive bacteria and fungal between the enzyme filter and control filters.(6)Maintenance, such as cleaning coil, humidifier, and air duct periodically, of an air conditioning system is most important to reduce air pollution caused by microorganism from an air conditioning system. Less