Ozone (O₃) and oxides of nitrogen (NO[subscript x]) are ubiquitous pollutants in many urban areas around the world. Though they mostly originate outdoors, human inhalation exposure to these pollutants largely occurs indoors, because of the large fraction of our time spent inside buildings. Exposure to O₃ and nitrogen dioxide (NO₂) has been associated with decreased respiratory function, onset of asthma, and cardiovascular events. Through laboratory testing, field exposure and modeling, this study evaluates the feasibility and long-term efficiency of using passive removal materials (PRMs) both indoors and outdoors for removal of O₃ and NO[subscript x]. Three photocatalytic coatings used outdoors and four indoor building materials were tested for their capacity to remove NO[subscript x] and O₃. Since materials outdoors experience a wider range of environmental conditions than indoors, their effects on NO[subscript x] removal by photocatalytic coatings were evaluated through full factorial experiments representative of summertime outdoor conditions in Southeast Texas. Photocatalytic coatings were also exposed to real outdoor environments for a year to assess their long-term viability. Indoor materials were exposed to real indoor environments for a six-month period and tested monthly for their capacity to remove O₃. Carbonyl emissions from these materials before and after exposure to O₃ were also tested at regular intervals during the six-month period. Finally, removal capacity of NO and NO₂ by new indoor building materials was tested as well. For outdoor PRMs, results suggest that the effect of certain environmental parameters (contact time, relative humidity, temperature) on NO[subscript x] removal effectiveness are consistent across different photocatalytic coatings, while other effects are coating specific. The type of semiconductor used and resistance to wear of the coating are important factors in its ability to retain removal efficacy over time. For indoor PRMs, two of the four materials tested, an activated carbon mat and perlite-based ceiling tiles, exhibited consistent O₃ removal effectiveness over time with low carbonyl emissions, both before and after ozonation. All materials except for activated carbon mat had higher post-ozonation than pre-ozonation emissions. Post-ozonation emissions were dominated by nonanal. Simulation of the use of indoor and outdoor PRMs on a model building through multi-zone/CFD modeling showed that indoor PRMs alone could lead to concentration reductions up to 18 % for O₃ and 23 % for NO₂ in rooms of the model building selected. Addition of PRMs on the outside of the building led to small reductions in pollutant concentrations in the air infiltrating into the building, leading to negligible changes in indoor concentrations. / text

Given the increasing awareness of indoor air quality (IAQ) and the direct correlation to human health, passive removal materials (PRM) have become known as a potential strategy for reducing occupant exposure to indoor air pollutants (Lu 2013). In recent studies, untreated natural wool fiber has been recognized as a PRM for removing formaldehyde, sulfur dioxide and nitrogen dioxide. These are common volatile organic compounds (VOCs) emitted from sources, such as building materials, fixtures, furnishings and cleaning supplies (Darling et al. 2012). Test chamber studies have shown that wool fiber can irreversibly remove up to 67% of these VOC’s in an interior environment (Curling et al 2012). When the toxins come in physical contact with the fiber, a chemical reaction occurs due to the amino-acid side chains within the keratin molecule. Increase in air-tight buildings has recently become a concern with the rising popularity of sustainable building practices, causing occupant exposure to these indoor air pollutants to rise (Weschler 2009). Beyond known adverse health effects, such as eye irritation and respiratory issues, formaldehyde has been designated by the International Agency for Research on Cancer (IARC) as a human carcinogen and is the leading cause for Sick Building Syndrome (SBS) (World Health Organization 2010). The interior cortex of a wool fiber is hydrophilic – highly water absorbent, and can absorb 1/3 its weight in moisture. Wool fiber has a unique wicking property that allows the fiber to absorb water vapor from the air in a regulating sense; absorbing when there is an excess moisture level and releasing the gained moisture when the surrounding atmosphere is less humid. This provides passive humidity regulation in an indoor environment, stabilizing the comfort level of 20-50% relative humidity (RH) without requiring higher air-conditioning or ventilation rates (Bingelli 2010). Wool also has excellent properties for optimizing indoor acoustics, as it absorbs acoustic energy via the friction of air being moved through the tiny spaces between fibers and reduces traveling noise and reverberation (Bingelli 2010). In an untreated, natural roving state the density of wool is ideal for acoustic control in conversational speech situations where 70dB or lower is present, such as meeting rooms, lobbies and restaurants. With the consideration of these properties, wool has the capability to improve the indoor environment quality (IEQ) and the health of occupants through the absorption of indoor air pollutants, humidity regulation and acoustic control. As Australia and the USA are among the top 3 wool producing countries, I will be working specifically with locally sourced wool from New South Wales and Texas as a basis for a sustainable IEQ intervention installation model that may be applied to future projects. The wool was obtained from local, small-scale fiber farms that implement hand processing in an effort to reduce toxins, in addition to lowering the manufacturing energy and transportation emission requirements. The local supply chain model provides increased environmental, social, economic and human health benefits to the design. Individual installations based on the vernacular wool fiber atrributes and interior climate needs will greatly increase the overall spatial environment, while also serving as an aesthetically pleasing piece of art. / text

Passive removal materials (PRMs) are building materials or furnishings that can effectively control indoor pollution without substantial formation of chemical byproducts and without energy penalty. To assess clay wall plaster as an effective PRM for improving air quality by controlling ozone, perceived air quality (PAQ) was determined in the presence of eight combinations of an emitting and reactive pollutant source (new carpet), clay plaster applied to gypsum wallboard, and chamber air with and without ozone. A panel of 18 to 23 human subjects assessed air quality in twin 30 m3 chambers using a continuous acceptability scale. Air samples were collected immediately prior to panel assessment to quantify concentrations of C5 to C10 saturated n-aldehydes and two aromatic aldehydes that are commonly produced by reaction of ozone with carpet. Perceived Air Quality was most acceptable and concentrations of aldehydes were lowest when only clay plaster or both clay plaster and carpet were present in the chambers without ozone. The least acceptable PAQ and the highest concentrations of aldehydes were observed when carpet and ozone were present together; addition of clay plaster for this condition improved PAQ and considerably decreased aldehyde concentrations. Ozone deposition and byproduct emissions of the clay wall plaster were also assessed using 48 liter stainless steel chambers. Clay plaster applied to gypsum wallboard that had been exposed in a test house (UTest House) for one year effectively removed 88% of the ozone, and emitted high aldehyde concentrations when exposed to high purity air that did not increase when the material was exposed to ozone. The outcome of these experiments leads to speculation that the clay plaster adsorbed contaminants in the test house and then re-emitted them upon exposure to clean air in the small chambers. / text