Clay-based materials for passive control of ozone and reaction byproducts in buildings
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Tropospheric ozone that infiltrates buildings reacts readily with many indoor materials and compounds that are commonly detected in indoor air. These reactions lead to lower indoor ozone concentrations. However, the products of ozone reactions may be irritating or harmful to building occupants. While active technologies exist (i.e., activated carbon filtration in HVAC systems) to suppress indoor ozone concentrations, they can be costly and/or infeasible for dwellings that do not have these systems. Passive methods of ozone removal are an interest of building environment researchers. This dissertation involves (1) a review of the state of the knowledge on building materials and coatings that are intended to passively remove indoor ozone, especially clay-based materials; (2) a compilation of current data on ozone removal and reaction byproduct formation for these materials; (3) a model for ozone removal effectiveness for a selected clay-based material that is implemented in a hypothetical home; (4) a survey of the effects of a clay-based coating with and without ozone and a reactant source on human perceptions of air quality; (5) an investigation of the long-term potential for passive control of indoor ozone by two different clay-based surface coatings that were exposed to real indoor environments; and (6) development of a location-specific model to estimate the monetary benefits versus costs of indoor ozone control using passive removal materials. The above tasks were completed through ongoing reviews of the literature, experimental studies conducted in small and large environmental chambers, and in the field. Results of these studies suggest that clay or materials made from clay are a viable material for passive reduction of indoor pollution, due in part to clay’s ability to catalyze ozone. Human sensory perceptions of indoor air quality were shown to significantly improve when a clay-based plaster was present in an ozonated environment. Based on modeling efforts, effective passive removal of indoor ozone is possible for realistic indoor scenarios when clay-based materials are implemented. There is a growing number of papers that are published on the subject of clay materials and indoor environmental quality, but few that investigate the longer term impacts and performance of clay materials, especially ones that have been exposed to real indoor environments.