Research On The Collection And Survival Of Airborne Microorganisms On The Fibrous Filter Media

In early 21st century, People's life and health were seriously affected by the outbreaks of some severe respiratory diseases, such as Service Acute Respiratory Syndrome (SARS) and the bird flu (H5N1 Killer Flu). And some high-tech fields, such as operating room, isolation ward, biological safety laboratory, medical care system, biomedical pharmacy engineering, food industry, are stricter with the control of airborne microorganisms than before. So the issue of indoor microbe contamination gradually draws widely and highly attentions of the world, and more research on bioaerosols removal and protection, especially the way of air filtration, is more important to be carried out.At the beginning of the subject, a bioaerosols removal efficiency model was established by combining the classic inert aerosol removal efficiency mathematical model with the characters of airborne microorganisms to predict the bioaerosols removal efficiency of the fibrous filter media. A classic Logistic mathematical model was used to analysis and to evaluate the growth extent of the microorganisms collected on the filter media. And a reentrainment model was used for the collected microorganisms on fibrous filter media to predict the theoretical probability of the secondary contamination. After that, according to the inner relationship of the above three separated models, an overall model was integrated to simulate the airborne microorganisms collection, survival and growth, and secondary contamination on the filters in the air-conditioning systems.And experiments were taken to prove the models of filtration and growth for the fibrous filter media by establishing an airborne microorganisms testing system. It was found that the bioaerosols removal efficiency model was suitable to predict the bio-protection performance of the fibrous filter media. Under the situation of low accuracy or lack of the data of microorganism characters including size, shape, size distribution, etc., the inert aerosol filtration model also could be used to predict the bioaerosols removal efficiency of the filter media. Other experiments were taken to simulate the different stages of the filter dust holding and tested the survival and growth of the filtrated microorganisms. After compared the experimental results with the theoretical data of Logistic model, it was found that the model could be fit to evaluate the survival and growth of the microorganisms which were filtrated on the filter media with different nutrition.In addition, the experiments tested the secondary contamination of the filter media under the situation of continuous ventilation. It showed that the results were seriously affected by some parameters, such as removal efficiency, the growth extent of microorganisms, face velocity, etc. However, microorganisms were detected at all downstream tests of the contaminated filter media, and all of them caused the secondary contamination in the air-conditioning system. So bioaerosols filtration is not the termination for long term bio-protection, further study on the new sterilization technology should be carried out. So the above theory and the experimental data will facilitate the next research on the bioaerosols filtration protection.