Browsing by Subject "Volatile organic compounds"
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Item Characterizing air composition of plumes from industrial plants using mobile measurements of volatile organic compounds(2022-12-02) Robertson, Rileigh L.; Misztal, Pawel K.Using a novel Vocus Proton Transfer Reaction Time of Flight Mass Spectrometer (Vocus-PTR-Tof-MS or Vocus) with sub parts per trillion (ppt; 10⁻¹²) detection limits for volatile organic compounds (VOCs), mobile measurements were collected while driving in Texas. Near industrial plants, rich and complex atmospheric composition was detected including compounds known as air toxics. This warranted further investigation using QGIS, a geospatial analysis software; concentration maps were produced to identify exact pollutant hotspots and plume patterns. Results revealed that the plumes, pollution clouds from a point source, were composed of high levels of aromatics (e.g. benzene, acetaldehyde, styrene, phenol, toluene, xylene, and naphthalene), highly oxidized compounds, and other classes. These VOCs are not detected by conventional, low-cost air quality monitors that have been implemented in the areas. With schools, homes, parks, and more near the properties, air profiles should be better assessed for resident safety. With PTRwid software, a full mass spectrum signature of VOCs was produced for the plumes at these locations to fingerprint their air composition. Out of more than 1000 VOCs detected, data reduction and quality control retained over 550 VOC specific ions. Many of these compounds are often found in sources like heated asphalt, fossil fuel burning, and other combustion processes that are known to be harmful to human health if not regulated properly. The rich chemical fingerprints will allow researchers to identify numerous pollution sources therefore aiding in source identification. The concentration maps and pollution fingerprints allow insights into pollution plume composition near these types of facilities and can quantify the exposure that workers and nearby residents may be subject to.Item Efficiency of photocatalytic oxidation air purifiers in removing single and multi-component volatile organic compounds and disinfection byproducts from indoor environments(2021-05-04) Abue, Pearl Achuoboro; Hildebrandt Ruiz, Lea; Misztal, PawelThe efficiency of a photocatalytic oxidation filter in removing single volatile organic compounds (VOCs) and a mixture of VOCs and disinfection byproducts was studied and compared to that of an activated carbon filter. The filters were set up in a modified portable Bissell400 air purifier unit and deployed in environmental chambers. Results from these experiments suggested that photocatalytic filters may operate more efficiently at higher ultraviolet light wavelengths of 400 nm. They also showed that the efficiency of photocatalytic filters exhibits some compound dependency with methyl ethyl ketone having an efficiency of 3% and 8%, ɑ-pinene having a removal efficiency of 14% and 12 % and Butyric acid having a removal efficiency of 37%. Filtration efficiencies are also impacted by air exchange rates, with higher air exchange rates yielding lower filter efficiencies, and by VOC concentrations, with lower concentrations yielding higher filter efficiencies. Time dependent changes in filter efficiency are also explored briefly and suggest that filter efficiencies decrease over time.Item Impact of variable emissions on ozone formation in the Houston area(2009-12) Pavlovic, Radovan Thomas, 1971-; Allen, David T.; McDonald-Buller, ElenaGround level ozone is one of the most ubiquitous air pollutants in urban areas, and is generated by photochemical reactions of oxides of nitrogen (NOx) and volatile organic compounds (VOCs). The effectiveness of emission reduction strategies for ozone precursors is typically evaluated using gridded, photochemical air quality models. One of the underlying assumptions in these models is that industrial emissions are nearly constant, since many industrial facilities operate continuously at a constant rate of output. However, recent studies performed in the Houston-Galveston-Brazoria area indicate that some industrial emission sources exhibit high temporal emission variability that can lead to very rapid ozone formation, especially when emissions are composed of highly reactive volatile organic compounds. This work evaluates the impact of variable emissions from industrial sources on ground-level ozone formation in Houston area, utilizing a unique hourly emission inventory, known as the 2006 Special Inventory, created as a part of the second Texas Air Quality Study. Comparison of the hourly emissions inventory data with ambient measurements indicated that the impact of the variability of industrial source emissions on ozone can be significant. Photochemical modeling predictions showed that the variability in industrial emissions can lead to differences in local ozone concentrations of as much as 27 ppb at individual ozone monitor locations. The hourly emissions inventory revealed that industrial source emissions are highly variable in nature with diverse temporal patterns and stochastic behavior. Petrochemical and chemical manufacturing flares, which represent the majority of emissions in the 2006 Special Inventory, were grouped into categories based on industrial process, chemical composition of the flared gas, and the temporal patterns of their emissions. Stochastic models were developed for each categorization of flare emissions with the goal of simulating the characterized temporal emission variability. The stochastic models provide representative temporal profiles for flares in the petrochemical manufacturing and chemical manufacturing sectors, and as such serve as more comprehensive input for photochemical air quality modeling.Item Indoor air quality in retail stores(2011-05) Rhodes, Joshua Daniel; Siegel, Jeffrey A.; Xu, YingRetail stores are understudied given the energy, occupant health, and potential sales impacts associated with poor indoor air quality (IAQ). There is also evidence of elevated pollutants in retail environments. This thesis is an exploration of the indoor air quality of retail stores. The first section of this thesis is a literature review on field investigations of the indoor air quality in retail buildings. Sixteen investigations report different measurements in 17 specific types of retail environments. Measurements vary depending on the specific investigation, but include VOCs, SVOCs, particles, microbiological species, and radon. When reported, indoor to outdoor ratios of almost all pollutants are greater than unity, suggesting the importance of indoor sources in retail environments. The second section of this thesis is an analysis of the whole store net emission factor for different retail environments. From the types of pollutants found in the retail store investigations, VOCs were the only pollutant group studied frequently enough to merit this analysis. The final section is an analysis of the potential for pollutant remediation strategies. Two methods, increasing air change rate and air cleaning, are considered with an analysis of the energy penalties associated with each.Item Performance assessment of TVOC sensors used in consumer-grade air quality monitors(2021-09-27) Bastami, Sepehr; Nagy, Gyorgy Zoltan; Kinney, KerryIndoor Air Quality (IAQ) has a direct impact on overall occupant health, especially respiratory and neural health. To ensure adequate indoor air quality, we must monitor the air by regularly sampling for pollutants of concern. One important category of air pollutants is VOCs: Volatile Organic Compounds. Some VOCs may be toxic at low concentrations while others require prolonged exposure at high concentrations to become a concern. Traditionally, measuring VOCs accurately has been prohibitively expensive and/or complicated. Recently, consumer-grade air quality monitors have been advertised as affordable counter parts to the expensive and complicated research-grade monitors and sensors. We studied the performance of a unique category of Total Volatile Organic Compounds sensor called a CMOS sensor. We assessed the performance of two brands of TVOC sensors used in three consumer-grade air quality monitors. We conducted a total of 5 experiments, 3 in a real home environment and 2 in a laboratory setting using a state-of-the-art air quality sampling device called the Vocus PTR-Tof. The consumer grade devices tend to exhibit some degree of uniformity in their patterns in response to pollution events, however, they can often deviate from one another in measuring actual concentration levels. The CMOS sensors studied suffer from a range of persistent challenges inherent to the CMOS technology, such as sensitivity and selectivity limitations. While improvements continue, more research is required to determine the extent to which these sensors may be useful and whether they can reliably and reasonably be used to assess indoor air qualityItem Smoking bans as particle source control and HVAC component loading due to airborne particle mass deposition(2006-12) Waring, Michael Shannon.; Siegel, Jeffrey A.This first part of this study assessed differences in the indoor air quality and occupancy levels in seventeen bars due to a city-wide smoking ban that took effect on September 1, 2005 in Austin, Texas, USA. The following were measured in each venue before and after the smoking ban: mean number of occupants, mean number of lit cigarettes, temperature, relative humidity, room volume, and PM2.5, CO, and CO2 concentrations. Additionally, VOC measurements were conducted at three of the venues. There was not a statistically significant change in occupancy, but the best estimate PM2.5 concentrations in the venues decreased 71 – 99%, a significant reduction in all venues, relative to the pre-ban levels; CO concentrations decreased significantly in all but one venue; and concentrations of VOCs known to be emitted from cigarettes decreased to below the detection limit for all but two common compounds. These results suggest that the smoking ban has effectively improved indoor air quality in Austin bars without an associated decrease in occupancy. The second part of this study modeled the amount of mass deposited on HVAC components for a month of operation (i.e., the loading rate) due to airborne particulate matter. The rate at which HVAC components load due to particle deposition is important from both an indoor air quality and energy perspective. The parameters that have the largest influence on the loading rates depend heavily on whether the building is residential or commercial. For the residential cases, the parameters that influenced the filter, coil, and supply-side duct loading rates the most were the Filtration and bypass, Coil properties, and Duct complexity parameters, respectively. For the commercial cases, which always employed some sort of intentional ventilation, the Ambient parameter was the most influential for all loading rates but the return-side ducts, for which the Emissions parameter was the most influential. Additionally, the Ambient and Emissions parameters ranked near the top of the most important parameters for many scenarios. For both the residential and commercial cases, the median over all cases for the filter loading rate was an order of magnitude larger than the median for the coil loading rate, which was an order of magnitude over the duct loading rates. The residential and commercial loading rates compare as follows: for median loading rates over all modeled scenarios, the commercial case for filter loading is approximately a factor of 89 over the residential case (65.39 versus 0.731 g/mo.); the commercial coil loading is approximately a factor of 39 over the residential case (1.83 versus 0.0468 g/mo.); and the commercial supply-side duct loading is approximately 114 times over the residential case (0.58 versus 0.0051 g/mo.). HVAC component loading causes higher pressure drops in the system, which can lead to reduced flow and reduced heating and cooling capacity for residential systems and increased fan energy usage for commercial systems. The results herein could be used to estimate filter changing and coil cleaning schedules with more information about how filter and coil loading affect pressure drop over time in real indoor environments. Additionally, the loading can have indoor air quality implications in the form of secondary pollutant formation or resuspension of biologically active material.