Removal of Particles from the Supply Air of Ventilation Systems Avoiding the Formation of Sensory Pollution Source:Delivery of Clean Air to Building Occupants

摘要

Used ventilation filters can act as sources of strong sensory pollution. The pollutants emitted from loaded particle filters may include irritating products of chemical reactions occurring on the filter surfaces. Most likely oxidation reactions, especially those driven by ozone, seem to play an important role. Sensory pollutants emitted from used filters can have significant adverse impact on occupant performance. Therefore, removal of particles from the supply air of ventilation systems without the subsequent emission of pollutants into the airstream seems to be essential. Correct maintenance of filter banks, including filter replacement in due time, is also important. The aim of this work was to gain more knowledge leading to a better understanding and solving a long recognized indoor environmental problem. The thesis deals with three core areas. Firstly, experiments were conducted to obtain better insight into the chemical processes occurring on the surfaces of used ventilation filters. Secondly, an economic evaluation was made to determine the impact of decreased occupant productivity caused by pollution from used filters on the overall costs and economic benefits associated with filtration. Finally, an experiment was designed to test the effect of different particle filters, activated carbon filters and their combinations on the perceived air quality after several months of continuous use. A commercially available HVAC filter that has low emissions of pollutants, even after substantial time in service, would mean a step forward towards finding an engineering solution to the problem. Additional measurements examined the effect of different pressure sensing techniques and several modifications of an air handling unit on the accuracy of the measurements of pressure drop over ventilation filters. Used and new filters were found to initially remove large amounts of ozone from the air that passed through. The initial ozone removal efficiency (~50%) decreased within an hour to a low and constant value (