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Measuring Atmospheric Ozone and Nitrogen Dioxide Concentration by Differential Optical Absorption Spectroscopy

Description: The main objective was to develop a procedure based on differential optical absorption spectroscopy (DOAS) to measure atmospheric total column of ozone, using the automated instrument developed at the University of North Texas (UNT) by Nebgen in 2006. This project also explored the ability of this instrument to provide measurements of atmospheric total column nitrogen dioxide. The instrument is located on top of UNT’s Environmental Education, Science and Technology Building. It employs a low cost spectrometer coupled with fiber optics, which are aimed at the sun to collect solar radiation. Measurements taken throughout the day with this instrument exhibited a large variability. The DOAS procedure derives total column ozone from the analysis of daily DOAS Langley plots. This plot relates the measured differential column to the airmass factor. The use of such plots is conditioned by the time the concentration of ozone remains constant. Observations of ozone are typically conducted throughout the day. Observations of total column ozone were conducted for 5 months. Values were derived from both DOAS and Nebgen’s procedure and compared to satellite data. Although differences observed from both procedures to satellite data were similar, the variability found in measurements was reduced from 70 Dobson units, with Nebgen’s procedure, to 4 Dobson units, with the DOAS procedure.A methodology to measure atmospheric nitrogen dioxide using DOAS was also investigated. Although a similar approach to ozone measurements could be applied, it was found that such measurements were limited by the amount of solar radiation collected by the instrument. Observations of nitrogen dioxide are typically conducted near sunrise or sunset, when solar radiation experiences most of the atmospheric absorption.
Date: December 2011
Creator: Jerez, Carlos J.
Partner: UNT Libraries

Spray dryer/baghouse system testing - CRADA 92-001. Final report

Description: A series of seven tests were conducted to evaluate the effectiveness of scrubbing both NO{sub 2} and SO{sub 2} in a spray dryer/baghouse system. The operating conditions specified were a high spray dryer inlet temperature (500{degrees}F), and a high spray dryer outlet temperature (250 to 300 {degrees}F). The data required to adequately evaluate the effectiveness of this technology is enclosed. Discussion of some of the variables as well as an itemized list of the testing information is part of the report.
Date: April 28, 1992
Creator: Pennline, H.W.
Partner: UNT Libraries Government Documents Department

Spectroscopic studies of the 110{degree}C thermal aging of PETN

Description: The 110{degrees}C thermal aging parameters, including initial rates of decomposition, of four types of pentaerythritol tetranitrate (PETN) over a period of ten months are presented. Both decomposition products nitric oxide, NO, and nitrogen dioxide, N0{sub 2} were monitored from multiple, hermetically-sealed, in vacuo samples. Nitric oxide appears to be the first nitrogen oxide product evolved. Nitrogen dioxide produced by abrupt thermal aging is more slowly converted to nitric oxide by a 1:1 process. The behavior of samples of RR5K PETN was significantly different from that of other powders studied. Further work is in progress to better define the thermal aging of RR5K PETN.
Date: July 30, 1992
Creator: Dosser, L. R. & Seliskar, C. J.
Partner: UNT Libraries Government Documents Department

Pollutant Removal Efficiency of Residential Cooking Exhaust Hoods

Description: Capture efficiency (CE) of exhaust from a natural gas cooking range was quantified for three common designs of residential range hoods in laboratory experiments: (A) microwave exhaust combination; (B) short hood with grease-screen-covered air inlet at bottom; and (C) deep, open hood exhausting at top. Devices were evaluated at varying installation heights, at highest and lowest fan settings, and with the hood installed 15 cm away from back wall with intent to improve CE for front burners. Each configuration was evaluated for the oven and for three cooktop burner combinations (two back, two front, one front and one back). At highest fan settings and standard installation against the wall, Hoods A and C captured back cooktop burner exhaust at > 90 percent and Hood B at > 80 percent. In this configuration, CE for front burner exhaust was 73-78 percent for Hoods A and C but only 46-63 percent for Hood B. CEs followed similar patterns but were substantially lower on the lowest fan speed. Installing the hood away from the wall improved CE for oven and front burners on Hood A at low speed, but substantially reduced CE for back burners for all hoods at low and high speed.
Date: July 1, 2011
Creator: Singer, Brett C.; Sherman, Alexander D.; Hotchi, Toshifumi & Sullivan, Douglas P.
Partner: UNT Libraries Government Documents Department

Hazard Assessment of Chemical Air Contaminants Measured in Residences

Description: Identifying air pollutants that pose a potential hazard indoors can facilitate exposure mitigation. In this study, we compiled summary results from 77 published studies reporting measurements of chemical pollutants in residences in the United States and in countries with similar lifestyles. These data were used to calculate representative mid-range and upper bound concentrations relevant to chronic exposures for 267 pollutants and representative peak concentrations relevant to acute exposures for 5 activity-associated pollutants. Representative concentrations are compared to available chronic and acute health standards for 97 pollutants. Fifteen pollutants appear to exceed chronic health standards in a large fraction of homes. Nine other pollutants are identified as potential chronic health hazards in a substantial minority of homes and an additional nine are identified as potential hazards in a very small percentage of homes. Nine pollutants are identified as priority hazards based on the robustness of measured concentration data and the fraction of residences that appear to be impacted: acetaldehyde; acrolein; benzene; 1,3-butadiene; 1,4-dichlorobenzene; formaldehyde; naphthalene; nitrogen dioxide; and PM{sub 2.5}. Activity-based emissions are shown to pose potential acute health hazards for PM{sub 2.5}, formaldehyde, CO, chloroform, and NO{sub 2}.
Date: May 10, 2010
Creator: Logue, J.M.; McKone, T.E.; Sherman, M. H. & Singer, B.C.
Partner: UNT Libraries Government Documents Department

Measurement of Helical Trajectories in Chemical Reactions by Ion Imaging

Description: During the first year of this grant we developed methods to measure the sense of rotation of the nitric oxide molecule (NO) using a circularly polarized laser probe and with ion imaging detection. The method was applied to the measurement of the correlation of rotational angular momentum orientation with recoil direction in the photodissociation of NO{sub 2}. [''Detection of ''ended'' NO recoil in the 355 nm NO2 photodissociation mechanism'', V.K. Nestorov and J.I. Cline, J. Chem. Phys. 111, 5287-5290 (1999)]. The photodissociation work was performed at the University of Nevada with additional, partial support from NSF. In the summer of 1999 this technique was transported to and implemented at the Combustion Research Facility at Sandia National Laboratory in Livermore, CA in a study of rotationally inelastic collisions of NO molecules with Ar atoms. The summer 1999 experiments at Sandia demonstrated that it is possible to detect collision-induced rotational alignment (preferred planes of rotation) for product molecules. During the late summer and fall of 1999 the P.I. and student James Barr developed a theoretical method for quantifying the angular momentum alignment and for extracting it from ion images. During the winter and spring of 2000 (January-May) the P.I. was in residence at Sandia National Laboratory in Livermore during a sabbatical leave from the University of Nevada. During this time the P.I. collaborated with Sandia P.I. Dr. David Chandler and Sandia postdoctorals Thomas Lorenz and Elisabeth Wade in experiments measuring both rotational alignment and rotational orientation (preferred senses of rotation) in collisions of NO with Ar. Graduate student James Barr continued these experiments at Sandia through the end of June 2000. The success of our experimental techniques for measuring collisional alignment and the theoretical methods we have developed for extracting quantitative alignment parameters from ion images. Spectroscopic probing of products by resonance-enhanced ...
Date: February 10, 2003
Creator: Cline, Joseph I.
Partner: UNT Libraries Government Documents Department

Chemiluminescent detection of organic air pollutants

Description: Chemiluminescent reactions can be used for specific and highly sensitive detection of a number of air pollutants. Among these are chemiluminescent reactions of ozone with NO or organics and reactions of luminol with a variety of oxidants. Reported here are studies exploring (1) the use of the temperature dependence of the chemiluminescent reactions of ozone with organic pollutants as a means of differentiating types of hydrocarbon classes and (2) the use of luminol techniques to monitor atmospheric concentrations of nitrogen dioxide (NO{sub 2}) and organic oxidants, specifically peroxyacyl nitrates (PANs). Coupling gas chromatography to the chemiluminescent detectors allows the measurement of individual species at very low concentrations.
Date: April 1, 1996
Creator: Marley, N.A.; Gaffney, J.S. & Chen, Yu-Harn
Partner: UNT Libraries Government Documents Department

Eddy correlation measurements of NO, NO{sub 2}, and O{sub 3} fluxes

Description: The micrometeorological technique of eddy correlation was used to measure the vertical fluxes of NO, NO{sub 2}, and ozone in rural North Carolian during spring 1995 as part of the Natural emission of Oxidant precurssors-Validation of techniques and Assessment (NOVA) field experiment. Net flux densities were measured at heights 5 and 10 m above an agricultural field with short corn plants and large amount of exposed bare soil between the rows. Large upward eddy fluxes of NO{sub 2} were seen, and strong NO emissions from the soil were measured by collaborators using environmental enclosures on the soil surface. Data indicate that about 50% of the nitrogen emitted from the soil as NO was converted into NO{sub 2} at 5 m. Rest of the emitted nitrogen may remain as NO flux and be returned back to the vegetation and soil by deposition. Divergence of the NO{sub 2} and O{sub 3} fluxes were detected between 5 and 10 m. This is consistent with likely net NO{sub 2} and O{sub 3} destruction rates. The data will be used to help develop parameterizations of the flux of nitrogen oxides into the lower troposphere.
Date: June 1, 1996
Creator: Gao, W.; Wesely, M.L.; Cook, D.R. & martin, T.J.
Partner: UNT Libraries Government Documents Department

Aircraft measurements of nitrogen dioxide and peroxyacyl nitrates using luminol chemiluminescence with fast capillary gas chromatography

Description: Peroxyacyl nitrates (PANs) and nitrogen dioxide (NO{sub 2}) are important trace gas species associated with photochemical air pollution. The PANs are in thermal equilibrium with the peroxyacetyl radical and NO{sub 2}. Because PANs are trapped peroxy radicals, they are an important indicator species of the photochemical age of an air parcel, as well as being a means of long-range transporting of NO{sub 2}, leading to the formation of regional ozone and other oxidants. Typically, PANs are measured by using a gas chromatograph with electron-capture detection (ECD). Once automated, this method has been shown to be reliable and quite sensitive, allowing the levels of PANs to be measured at low parts per trillion in the troposphere. Unfortunately, a number of other atmospheric gases also have strong ECD signals or act as inferences and limit the speed in which the analysis can be completed. Currently, the shortest analysis time for PAN is approx. 5 minutes with ECD. The authors recent examined the luminol detection of NO{sub 2} and PANs using gas capillary chromatography for rapid monitoring of these important trace gases. Analysis of the PANs (PAN, PPN, and PBN) and NO{sub 2} in one minute has been demonstrated in laboratory studies by using this approach. Reported here are modifications of this instrument for aircraft operation and preliminary results from test flights taken near Pasco, Washington in August of 1997.
Date: September 1997
Creator: Gaffney, J. S.; Marley, N. A. & Drayton, P. J.
Partner: UNT Libraries Government Documents Department

The detection of mixtures of NO{sub x}`s with hydrogen using catalytic metal films on the Sandia Robust Sensor with pattern recognition

Description: Microsensors often do not have the selectivity to chemical species available in large laboratory instruments. A new type of pattern recognition algorithm is used to classify mixtures of H{sub 2} with NO{sub 2} and O{sub 2}. The microsensors used are thin film catalytic metal field effect transistors and chemiresistors on the Sandia Robust Sensor platform. For this study pure Pd thin films and Pd/Ni alloys are shown to provide good classification of mixtures containing NO{sub 2} from those containing O{sub 2} or no oxidant.
Date: December 31, 1994
Creator: Hughes, R.C.; Osbourn, G.C.; Bartholomew, J.W. & Rodriguez, J.L.
Partner: UNT Libraries Government Documents Department

Fast gas chromotography with luminol detection for measurement of nitrogen dioxide and PANs.

Description: Fast capillary gas chromatography has been coupled to a luminol-based chemiluminescence detection system for the rapid monitoring of nitrogen dioxide and peroxyacyl nitrates. A first-generation instrument was described recently (Gaffney et al., 1998). This system is capable of monitoring nitrogen dioxide and peroxyacyl nitrates (PANs; to and including the C4 species) with 1-min time resolution. This is an improvement by a factor of five over gas chromatography methods with electron capture detection. In addition, the luminol method is substantially less expensive than laser fluorescent detection or mass spectroscopic methods. Applications in aircraft-based research have been published electronically and will appear shortly in Environmental Science and Technology (Gaffney et al., 1999a). An improved version of the instrument that has been designed and built makes use of a Hammamatsu photon-counting system. Detection limits of this instrumentation are at the low tens of ppt. The range of the instrument can be adjusted by modifying sampling volumes and detection counting times. A review of past work and of recent application of the instrumentation to field measurements of nitrogen dioxide and PANs is presented. The data clearly indicate that the luminol approach can determine the target species with time resolution of less than 1 min. Examples of applications for estimation of peroxyacetyl radical concentrations and nitrate radical formation rates are also presented. This instrumentation can further be used for evaluation of surfaces for loss of nitrogen dioxide and PANs, phenomena of possible importance for sampling interfaces and chamber wall design. Our high-frequency field data clearly indicate that the ''real world'' is not well mixed and that turbulent mixing and plume-edge chemistries might play an important role in urban- and regional-scale interactions. Dynamic flow systems might be required to evaluate such effects in new-generation chamber studies.
Date: September 30, 1999
Creator: Gaffney, J. S.; Marley, N. A. & Drayton, P. J.
Partner: UNT Libraries Government Documents Department

Autonomous Optical Sensor System for the Monitoring of Nitrogen Dioxide from Aging Rocket Propellant

Description: An optical sensor system has been developed for the autonomous monitoring of NO{sub 2} evolution in energetic material aging studies. The system is minimally invasive, requiring only the presence of a small sensor film within the aging chamber. The sensor material is a perylene/PMMA film that is excited by a blue LED light source and the fluorescence detected with a CCD spectrometer. Detection of NO{sub 2} gas is done remotely through the glass window of the aging chamber. Irreversible reaction of NO{sub 2} with perylene, producing the non-fluorescent nitroperylene, provides the optical sensing scheme. The rate of fluorescence intensity loss over time can be modeled using a numerical solution to the coupled diffusion and a nonlinear chemical reaction problem to evaluate NO{sub 2} concentration levels. The light source, spectrometer, spectral acquisition, and data processing were controlled through a Labivew program run by a laptop PC. Due to the long times involved with materials aging studies the system was designed to turn on, warm up, acquire data, power itself off, then recycle at a specific time interval. This allowed the monitoring of aging HE material over the period of several weeks with minimal power consumption and stable LED light output. Despite inherent problems with gas leakage of the aging chamber they were able to test the sensor system in the field under an accelerated aging study of rocket propellant. They found that the propellant evolved NO{sub 2} at a rate that yielded a concentration of between 10 and 100 ppm. The sensor system further revealed that the propellant, over an aging period of 25 days, evolves NO{sub 2} with cyclic behavior between active and dormant periods.
Date: September 1, 2001
Creator: COX, TRISHA D.; SINGH, SEEMA; HUNTER, JOHN A.; JONES, GARY D.; SINCLAIR, MICHAEL B.; ROHWER, LAUREN E. S. et al.
Partner: UNT Libraries Government Documents Department

Short-Time-Response measurements of nitrogen dioxide and peroxyacetyl nitrate by fast capillary gas chromatography with luminol detection.

Description: The interaction of hydrocarbons and nitrogen oxides in sunlight to produce photochemical smog has been well studied over the years. In the past, the workhorse for the measurement of NO{sub 2}and NO was the chemiluminescent reaction with ozone. This method has detection limits of approximately 0.5 ppb in most commercial instruments, but it cannot detect NO{sub 2} directly; the instrument detects NO and uses hot catalytic surfaces to decompose all other nitrogen oxides (including NO{sub 2}) to NO for detection (l). The main problem with the method is the inherent difficulty in detecting excited NO{sub 2}, which emits over a broad region beginning at approximately 660 nm and has a maximum at 1270 nm, thus requiring a red-shifted photomultiplier for detection. The use of luminol for direct chemiluminescent detection of NO{sub 2} was demonstrated to have greater inherent sensitivity (detection limits of 5 ppt) than the indirect ozone chemiluminescence detection (2). In the luminol system, a gas-liquid reaction leads to light emission with a maximum at approximately 425 nm, at the maximum sensitivity for most photomultiplier tubes. This emission is responsible for the increased detection sensitivities. The biggest problem with this method for direct measurement of NO{sub 2} has been interference due to other soluble oxidants, particularly peroxyacyl nitrates (PANs).
Date: December 7, 2000
Creator: Marley, N. A.; Gaffney, J. S. & Drayton, P. J.
Partner: UNT Libraries Government Documents Department

CLOUD CHEMISTRY.

Description: Clouds present substantial concentrations of liquid-phase water, which can potentially serve as a medium for dissolution and reaction of atmospheric gases. The important precursors of acid deposition, SO{sub 2} and nitrogen oxides NO and NO{sub 2} are only sparingly soluble in clouds without further oxidation to sulfuric and nitric acids. In the case of SO{sub 2} aqueous-phase reaction with hydrogen peroxide, and to lesser extent ozone, are identified as important processes leading to this oxidation, and methods have been described by which to evaluate the rates of these reactions. The limited solubility of the nitrogen oxides precludes significant aqueous-phase reaction of these species, but gas-phase reactions in clouds can be important especially at night.
Date: March 2001
Creator: Schwartz, S. E.
Partner: UNT Libraries Government Documents Department

Measurements of nonmethane hydrocarbons in Phoenix, Arizona

Description: Nonmethane hydrocarbons (NMHCs) are precursors to oxidant formation. They are oxidized by hydroxyl radical (OH), forming a complex mixture of peroxy radicals that oxidize NO to NO{sub 2} without consuming ozone (O{sub 3}) and thus allow O{sub 3} to increase in the atmospheric boundary layer. The reactivities of the NMHCs that compose biogenic and anthropogenic emissions vary greatly. For example, isoprene, which is emitted by deciduous vegetation, has an atmospheric lifetime with respect to oxidation by OH of about 20 min in polluted air ([OH] = 10{sup 7} radicals cm{sup {minus}3}). The atmospheric lifetimes of 2-methylpropene, 2-methylbutane, and the xylenes, which are found in vehicle emissions, are approximately 30 min, 7 hr, and 1.5 hr, respectively. The authors made measurements of the NMHCs at a surface site and aloft aboard the Battelle Gulfstream (G-1) aircraft, as part of an air quality study in the Phoenix area during May 1998. Diurnal variations in the NMHC distributions and their propene-equivalent concentrations are used to examine origins and reactivities of the air masses that were sampled at the surface site.
Date: October 12, 1999
Creator: Doskey, P. V.; Kotamarthi, V. R. & Rudolph, J.
Partner: UNT Libraries Government Documents Department

Energy states and energy flow near the transition states of unimolecular reactions

Description: The use of lasers with jet-cooled samples has improved energy and angular momentum resolution for the reactant and time resolution for the rate constant by orders of magnitude. The resolution of product quantum states has added a new dimension to unimolecular dynamics. In the past, the geometry, barrier height and vibrational frequencies of the transition state in RRKM theory were adjusted to fit thermal unimolecular reaction rate data. There have been successful quantitative tests of the ability of ab initio theory to calculate transition state geometries accurately and barrier heights to a few kJ/mol for simple molecules. Predicted frequencies tend to be somewhat too high for the softest modes which are of most importance in determining rates; however, the basic normal modes and sequence of frequencies seem to be correctly predicted. RRKM theory can be used with ab initio results to predict rate constants to within a factor of two or three and may be used for quantitative extrapolation to conditions not accessible in the laboratory but important in practical situations. Experiments on single molecular eigenstates have revealed quantum statistical fluctuations in rates which are predicted quantitatively in the appropriate extension of RRKM theory. Many experiments seeking to demonstrate non-statistical or non-RRKM dynamics have demonstrated the very wide range of applicability of the RRKM model. A few such experiments have demonstrated a lack of complete vibrational energy randomization in a reactant molecule. Dynamical theory has provided an exact quantum analog to RRKM theory which will combine with future experiments to define the extent to which quantized motion along the reaction coordinate and coupling between the reaction coordinate and vibrational degrees of freedom at the transition state are important. 42 refs., 11 figs.
Date: October 1, 1994
Creator: Moore, C.B.
Partner: UNT Libraries Government Documents Department

Chemical response of methane/air diffusion flames to unsteady strain rate

Description: Effects of unsteady strain rate on the response of methane/air diffusion flames are studied. The authors use the finite-domain opposed flow configuration in which the nozzle exit velocity is imposed as a function of time. The GRI mechanism v2.11 is used for the detailed methane/air chemistry. The response of individual species to monochromatic oscillation in strain rate with various frequencies reveals that the fluctuation of slow species, such as CO and NO{sub x}, is more rapidly suppressed as the flow time scale decreases. It is also observed that the maximum CO concentration is very insensitive to the variation in the scalar dissipation rate. An extinction event due to an abrupt imposition of high strain rates is also simulated by an impulsive velocity with various frequencies. For a fast impulse, a substantial overshoot in NO{sub 2} concentration is observed after extinction. Finally, the overall fuel burning rate shows a nonmonotonic response to the variation in characteristic unsteady time scale, while the emission indices for NO{sub x} shows monotonic decay in response as frequency is increased.
Date: March 1, 1998
Creator: Im, H.G.; Chen, J.H. & Chen, J.Y.
Partner: UNT Libraries Government Documents Department

Vapor space characterization of waste Tank 241-BY-111: Results from samples collected on November 15, 1994

Description: This report describes results of the analyses of tank-headspace samples taken from the Hanford waste Tank 241-BY-111 (referred to as Tank By-111). Pacific Northwest Laboratory (PNL) contracted with Westinghouse Hanford company (WHC) to provide sampling devices and to analyze inorganic and organic analytes collected from the tank headspace and ambient air near the tank. The target analytes for TO- 14 compounds were extended to include 14 analytes identified by the Toxicological Review Panel for Tank C-103 and reported by Mahlum et al. (1994). Program management included these analytes for future tank analyses as identified in the fiscal year work plan. This plan is attached to a letter dated 9/30/94 and addressed to Mr. T.J. Kelly of WHC. The plan also requires PNL to analyze for the permanent gases as shown in Table 3.7. The sample job was designated S4083, and samples wee collected by WHC on November 16, 1994, using the vapor sampling system (VSS). The results of the analyses are expected to be used to estimate the potential toxicity of tank-headspace gas as described in Data Quality Objectives for Generic In-Tank Health and Safety Vapor Issue Resolution, WHC-SD-WM-DQO-002, Rev. 0.
Date: June 1, 1995
Creator: Lucke, R.B.; Ligotke, M.W. & McVeety, B.D.
Partner: UNT Libraries Government Documents Department

Do indoor environments in schools influence student performance? A review of the literature

Description: Limited research is available on potential adverse effects of school environments on academic performance, despite strong public concern. We examine the scientific evidence relevant to this relationship by reviewing available research relating schools and other indoor environments to human performance or attendance. As a primary focus, we critically review evidence for direct relationships between indoor environmental quality (IEQ) in buildings and performance or attendance. As a secondary focus, we summarize, without critique, evidence on potential connections indirectly linking IEQ to performance or attendance: relationships between IEQ and health, between health and performance or attendance, and between attendance and performance. The most persuasive direct evidence showed increases in indoor concentrations of nitrogen dioxide and outdoor concentrations of several specific pollutants to be related to reduced school attendance. The most persuasive indirect evidence showed indoor dampness and microbiologic pollutants to be related to asthma and respiratory infections, which have in turn been related to reduced performance and attendance. Furthermore, a substantial scientific literature links poor IEQ (e.g., low ventilation rate, excess moisture or formaldehyde) with respiratory and other health effects in children and adults. Overall, evidence suggests that poor IEQ in schools can influence the performance and attendance of students, primarily through health effects from indoor pollutants. Also, inadequate IEQ in schools seems sufficiently common to merit strong public concern. Evidence is available to justify (1) immediate actions to protect IEQ in schools and (2) focused research on exposures, prevention, and causation, to better guide policies and actions on IEQ in schools.
Date: November 24, 2004
Creator: Mendell, Mark J. & Heath, Garvin A.
Partner: UNT Libraries Government Documents Department

Performance of Installed Cooking Exhaust Devices

Description: The performance metrics of airflow, sound, and combustion product capture efficiency (CE) were measured for a convenience sample of fifteen cooking exhaust devices, as installed in residences. Results were analyzed to quantify the impact of various device- and installation-dependent parameters on CE. Measured maximum airflows were 70% or lower than values noted on product literature for 10 of the devices. Above-the-cooktop devices with flat bottom surfaces (no capture hood) – including exhaust fan/microwave combination appliances – were found to have much lower CE at similar flow rates, compared to devices with capture hoods. For almost all exhaust devices and especially for rear-mounted downdraft exhaust and microwaves, CE was substantially higher for back compared with front burner use. Flow rate, and the extent to which the exhaust device extends over the burners that are in use, also had a large effect on CE. A flow rate of 95 liters per second (200 cubic feet per minute) was necessary, but not sufficient, to attain capture efficiency in excess of 75% for the front burners. A-weighted sound levels in kitchens exceeded 57 dB when operating at the highest fan setting for all 14 devices evaluated for sound performance.
Date: November 1, 2011
Creator: Singer, Brett C.; Delp, William W.; Apte, Michael G. & Price, Philip N.
Partner: UNT Libraries Government Documents Department