There are many U.S. health-related standards for ozone that aim to limit exposure to ozone. The potential for ozone emission from electrically connected air cleaners is well- known and has led to standards and regulations for portable indoor air cleaning devices, which emit ozone at measured rates of 0.056 – 13.4 mg/hr. However, there is evidence that some in-duct air cleaners may actually emit more ozone than portable air cleaners, despite being exempt from most regulations due to the lack of a suitable test method for measuring ozone generation. To explore if in-duct cleaners actually do emit ozone, I investigated seven commercially available residential in-duct air cleaning devices. These devices used one of two broad technologies as means of air cleaning: UV light or electrical corona. The lowest measured emission rates came from two air cleaners that utilized UV light technology and were 0.309 ± 1.7 mg/hr, which was likely below the detection limit of the apparatus and method, and 4.29± 1.5 mg/hr. Three of the air cleaners tested, also with UV lamps, were of the same brand and model yet exhibited differing emission rates, ranging from 7.44± 1.6 mg/hr to 15.8± 2.6 mg/hr. These three air cleaners were classified as medium emitters and also utilized UV light technology. The high median measured emission rates were measured from both an air cleaner utilizing electrical corona technology, 30.2 ± 4.0 mg/hr, and UV light technology, 29.4 ± 3.9 mg/hr. These experimental results confirm that some in-duct air cleaners are able to generate more ozone than some portable air cleaners and also suggest potential health risks to the indoor environment. / text

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

A comprehensive Ultrapure Water (UPW) simulator program has been developed to model each unit process in UPW systems, including the entire dynamic system in real time. The program estimates the removal efficiencies for contaminants generated in semiconductor processes and in municipal water supplies. Calculations are performed using flow balance and concentration profile determinations at each unit process throughout the system. Simulator validation occurred using existing industrial facilities. Spent rinsewater (SRW) recycling in semiconductor facilities has been shown to provide significant UPW quality improvements. Contrary to many perceptions, this recycling is not a compromise to the quality, but an improvement. Benefits to the cost, reliability, and environmental improvements have also been identified. Processing risks have also been identified as the use of UPW with even minute quantities of contaminants, in particular the organic contaminants, could cause process problems. The simulator has been shown to be quite capable of predicting the impact on UPW quality due to excursions in SRW quality from semiconductor processes. Photolithography is a primary semiconductor process where organic photoresist is removed from wafers with corrosive chemistries. SRW is contaminated with both organic residues and corrosive chemicals. Ozonated UPW has recently become an alternative chemical for photoresist removal. A single-wafer tool was fabricated out of quartz designed for various processes. With direct observation of the wafer possible. Ultraviolet light experiments were also performed, directing light through the quartz, process solution, and onto the wafer. Experimental procedures were developed to study the effects of turbulence, wafer pretreatment, in-situ process treatments, and vibration on the kinetics and mechanism of photoresist removal by ozonated UPW. Data was obtained to determine which oxidation pathway was dominant; direct ozone, or indirect oxidation through radical formation. Intermediate products were determined using Fourier Transform Infrared Spectroscopy. Two distinct mechanisms were observed: film dissolution via a uniform sheeting method, and a non-uniform vapor-phase bubble mechanism where film dissolution occurred underneath the bubble. Models were developed that describe the film removal under both mechanisms. The uniform sheeting model describes typical process conditions in current tools. This model was validated and found in good agreement with experimental data.

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Author's manuscript for published article. See Additional Links field for link to published version. / Ethylene production by different needle age classes was characterized using a mercuric perchlorate traps in natural populations of two ponderosa pine varieties (Pinus ponderosa var. arizonica [Engelm] Shaw and var. ponderosa Dougl. ex Laws.) and Jeffery pine (Pinus leffrevi Grev. and Balf.). All ozone -exposed populations contained individuals which were symptomatic and asymptomatic with respect to visible ozone injury. Ethylene production of different needle age classes was also characterized in Pinus ponderosa var. ponderosa seedlings grown in open top ozone fumigation chambers. Older age class needles produce more ethylene than younger age class needles. Needles of both P. ponderosa var. ponderosa and P. jeffreyi exhibiting ozone injury in the field produced significantly (p >0.05) higher levels of ethylene than asymptomatic conspecifics. Seedlings exposed to highest treatment level of ozone in the fumigation study produced the highest levels of ethylene followed by fumigation with medium and low ozone concentrations and carbon filtered air. These data indicate that measurement of ethylene in conifer needles as a measure of stress needs to be calibrated for needle age class. It also suggests that the sensitivity of a tree to ozone injury may be regulated by the inherent ability of the individual to produce ethylene.

There has been a recent surge in the number of people using reclaimed water systems for personal use. Because of this, it is getting more and more important for easy-to-use and cost effective disinfectants on the market for consumer application. This study looked at the efficacy of three disinfectants, trichloromelamine, ozone and acetic acid, for their ability to reduce the number of waterborne pathogens. Four samples of TCM were tested in a 10mL contaminated water:1mL TCM solution ratio and plated for both total plate counts and to check for generic E.coli. It was found that one of the four samples of TCM (TCM 3) was able to not only give a percent reduction of 92.54%, but it also killed the E.coli that was present in the water. TCM1 had an average percent reduction of 98.77, TCM2's percent reduction was 97.34, and TCM4's: 87.64. This was not the most effective disinfectant, however. Similar tests were done with ozone, ozone that was mixed with brine water, and ozone that was mixed with acetic acid, as well as pure acetic acid. Ozonated brine water, and ozone mixed with acetic acid were both nearly 100% effective at reducing bacterial load in the water samples (99.989 and 100%, respectively). The pure ozone was not nearly as effective, with a percent reduction of 85.7%. These results indicate that TCM and ozone could possibly be effective tools for the consumer to use to disinfect water holding tanks, however, more testing needs to be done in order to find out exactly how effective these products are in the long term, as well as to find the contact time needed for effective kill by TCM.

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