VENTILATION CONTROL TO REDUCE AIRBORNE CONTAMINANTS

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Studies have shown conclusively that airborne contaminant levels in swine confinements are typically of a sufficient level to pose a health hazard to workers in that occupation. In addition to a particulate component that can reach levels of 26 mg/m3, gases present in confinements in high amounts include methane, hydrogen sulfide, ammonia, and carbon dioxide. Recognized respiratory diseases of swine farmers include upper airway inflammation, an asthma-like syndrome, and chronic airflow limitations. Ventilation systems associated with swine confinements are largely designed to provide a comfortable climate for the pigs. However, because confinements are operated on a for-profit basis, costs associated with operating the ventilation system are typically kept to a minimum by minimizing fan usage which results in maintaining high airborne contaminant levels. This research proposal involves the application of feedback control theory to design an automated confinement ventilation system that will operate the system in such a way as to simultaneously minimize the competing needs to minimize both costs and contaminant levels. Prior to the design and testing of such a control method, an analysis of the time-varying nature of two contaminants (total dust concentration and ammonia levels) and two climate factors (temperature and humidity) will be performed over the course of year in a swine confinement. This work will result in information needed to ascertain the accuracy of real-time sensors used to measure these four "output" variables as well as to indicate the noise qualities of the measurement signal. Sequential measurements of this type during a change in fan speed will also be used to determine, and mathematically model, the dynamic relationship between a change in output variable and a change in fan speed. From a knowledge of the noise qualities and dynamic behavior of the output variables, the design and simulation of several possible feedback control methods will be performed using software specifically developed for this purpose. A final aspect of the proposed research will involve a series of tests of the best candidate control methods with the use of a full-scale ventilation-testing facility. Future work would then involve the development and testing of the best control method in an actual facility; the development of other engineering control methods to minimize the production and migration of airborne contaminants in a confinement; and a verification of the control method's utility by measuring the change in contaminant levels and the lung function of workers.