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Vapor Concentration (vapor + concentration)
Selected AbstractsChemical Agent Simulant Release from Clothing Following Vapor ExposureACADEMIC EMERGENCY MEDICINE, Issue 2 2010Robert J. Feldman MD ACADEMIC EMERGENCY MEDICINE 2010; 17:1,4 © 2010 by the Society for Academic Emergency Medicine Abstract Objectives:, Most ambulatory victims of a terrorist chemical attack will have exposure to vapor only. The study objective was to measure the duration of chemical vapor release from various types of clothing. Methods:, A chemical agent was simulated using methyl salicylate (MeS), which has similar physical properties to sulfur mustard and was the agent used in the U.S. Army's Man-In-Simulant Test (MIST). Vapor concentration was measured with a Smiths Detection Advanced Portable Detector (APD)-2000 unit. The clothing items were exposed to vapor for 1 hour in a sealed cabinet; vapor concentration was measured at the start and end of each exposure. Clothing was then removed and assessed every 5 minutes with the APD-2000, using a uniform sweep pattern, until readings remained 0. Results:, Concentration and duration of vapor release from clothing varied with clothing composition and construction. Lightweight cotton shirts and jeans had the least trapped vapor; down outerwear, the most. Vapor concentration near the clothing often increased for several minutes after the clothing was removed from the contaminated environment. Compression of thick outerwear released additional vapor. Mean times to reach 0 ranged from 7 minutes for jeans to 42 minutes for down jackets. Conclusions:, This simulation model of chemical vapor release demonstrates persistent presence of simulant vapor over time. This implies that chemical vapor may be released from the victims' clothing after they are evacuated from the site of exposure, resulting in additional exposure of victims and emergency responders. Insulated outerwear can release additional vapor when handled. If a patient has just moved to a vapor screening point, immediate assessment before additional vapor can be released from the clothing can lead to a false-negative assessment of contamination. [source] Characterization of the fire environments in central offices of the telecommunications industryFIRE AND MATERIALS, Issue 3 2003Archibald Tewarson Abstract Eight free burning and two sprinklered fire tests were performed with electrical cable trays and live digital switch racks in a large enclosure to simulate telecommunications central office (TCO) fires started by electrical overheating. Very-slow-growing (non-flaming), slower-growing (partially flaming) and low-intensity-faster-growing (flaming) fires releasing gray-white, gray, and black smoke, respectively, were observed in the tests. Under quiescent conditions present in the unvented enclosure fire tests for cables, very-slow-growing fires were detected in about 1452 s, whereas the slower-growing fires were detected in about 222 s by commercial fire detectors. Under ventilation conditions typical of TCOs, detection times were very similar for the five types of commercial TCOs fire detectors used in the tests. The average detection times for slower-growing fires (cable fires) and low-intensity-faster-growing fires (digital switch rack fires) were 242±17% and 249±11%s respectively. The TCO procedures to reduce smoke damage from fires (on fire detection, inlet ventilation flow is turned off and exhaust flow is turned on) were found to be beneficial. The extent of smoke damage decreased significantly with an increase in the exhaust flow rate. The chloride ion mass deposition suggested that equipment recovery would be possible in the smoke environment if the cable vapor concentration could be reduced below about 3 g/m3. The metal corrosion rate was found proportional to the 0.6th power of the smoke concentration, similar to that found for the corrosion of metal surfaces exposed to aqueous solutions of HCl and HNO3 and for acid rain with no protective layer at the surface. Sprinkler water was found to wash down the smoke deposits on the surfaces with little indication of corrosion enhancement. Copyright © 2003 John Wiley & Sons, Ltd. [source] Vapor Intrusion in Homes over Gasoline-Contaminated Ground Water in Stafford, New JerseyGROUND WATER MONITORING & REMEDIATION, Issue 1 2006Paul F. Sanders The potential for chemical vapor intrusion from contaminated ground water to the interior of homes was investigated at a site with a leaking underground gasoline storage tank in Stafford Township, New Jersey. This location exhibited conditions favorable to vapor intrusion, with sand soil and a water table depth of 3.3 m. Concentrations of volatile organic chemicals in the ground water were as high as 82 mg/L for total benzene, toluene, ethylbenzene, and xylene (BTEX) and up to 590 mg/L for methyl- t -butyl ether (MTBE). Soil vapor samples at multiple depths were taken adjacent to several homes. Inside the homes, air samples were taken on the main floor, in the basement, and under the foundation slab. Despite high ground water concentrations, only one home had measurable impacts to indoor air quality attributable to some of the ground water contaminants. In this house, the BTEX chemicals were not detected in the basement, indicating a lack of indoor air impacts from the ground water for these chemicals. Oxygen measurements suggested that degradation attenuated these chemicals as they diffused through the vadose zone. However, MTBE, 2,2,4-trimethylpentane (isooctane), and cyclohexane were found in the indoor air. The first two of these chemicals served as gasoline-specific tracers and indicated that vapor intrusion was occurring. Attenuation factors (the ratio of the indoor air concentration to a source soil vapor concentration) for the BTEX chemicals between the ground water and the indoor air were <1 × 10,5, and for MTBE was 1.2 × 10,5. Attenuation factors between the deep-soil vapor and the basement air were as follows: BTEX compounds, <1 × 10,5; MTBE, 2.2 × 10,5; 2,2,4-trimethylpentane, 3.6 × 10,4; and cyclohexane, 1.2 × 10,4. Attenuation factors between the subslab vapor and the basement air were 7 to 8 × 10,3. [source] A simple reactive gasdynamic model for the computation of gas temperature and species concentrations behind reflected shock waves,INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 4 2008H. Li A simple gasdynamic model, called CHEMSHOCK, has been developed to predict the temporal evolution of combustion gas temperature and species concentrations behind reflected shock waves with significant energy release. CHEMSHOCK provides a convenient simulation method to study various sized combustion mechanisms over a wide range of conditions. The model consists of two successive suboperations that are performed on a control mass during each infinitesimal time step: (1) first the gas mixture is allowed to combust at constant internal energy and volume; (2) then the gas is isentropically expanded (or compressed) at frozen composition to the measured pressure. The CHEMSHOCK model is first validated against results from a one-dimensional reacting computational fluid dynamics (CFD) code for a representative case of heptane/O2/Ar mixture using a reduced mechanism. CHEMSHOCK is found to accurately reproduce the results of the CFD calculation with significantly reduced computational time. The CHEMSHOCK simulation results are then compared to experimental results, for gas temperature and water vapor concentration, obtained using a novel laser sensor based on fixed-wavelength absorption of two H2O rovibrational transitions near 1.4 ,m. Excellent agreement is found between CHEMSHOCK simulations and measurements in a progression of shock wave tests: (1) in H2O/Ar, with no energy release; (2) in H2/O2/Ar, with relatively small energy release; and (3) in heptane/O2/Ar, with large energy release. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 189,198, 2008 [source] Transport mechanisms and performance simulation of a PEM fuel cellINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 6 2008Geng-Po Ren Abstract A three-dimensional, gas,liquid two-phase flow and transport model has been developed and utilized to simulate the multi-dimensional, multi-phase flow and transport phenomena in both the anode and cathode sides in a proton exchange membrane (PEM) fuel cell and the cell performance with different influencing operational and geometric parameters. The simulations are presented with an emphasis on the physical insight and fundamental understanding afforded by the detailed distributions of velocity vector, oxygen concentration, water vapor concentration, liquid water concentration, water content in the PEM, net water flux per proton flux, local current density, and overpotential. Cell performances with different influencing factors are also presented and discussed. The comparison of the model prediction and experimental data shows a good agreement. Copyright © 2007 John Wiley & Sons, Ltd. [source] Chemical Agent Simulant Release from Clothing Following Vapor ExposureACADEMIC EMERGENCY MEDICINE, Issue 2 2010Robert J. Feldman MD ACADEMIC EMERGENCY MEDICINE 2010; 17:1,4 © 2010 by the Society for Academic Emergency Medicine Abstract Objectives:, Most ambulatory victims of a terrorist chemical attack will have exposure to vapor only. The study objective was to measure the duration of chemical vapor release from various types of clothing. Methods:, A chemical agent was simulated using methyl salicylate (MeS), which has similar physical properties to sulfur mustard and was the agent used in the U.S. Army's Man-In-Simulant Test (MIST). Vapor concentration was measured with a Smiths Detection Advanced Portable Detector (APD)-2000 unit. The clothing items were exposed to vapor for 1 hour in a sealed cabinet; vapor concentration was measured at the start and end of each exposure. Clothing was then removed and assessed every 5 minutes with the APD-2000, using a uniform sweep pattern, until readings remained 0. Results:, Concentration and duration of vapor release from clothing varied with clothing composition and construction. Lightweight cotton shirts and jeans had the least trapped vapor; down outerwear, the most. Vapor concentration near the clothing often increased for several minutes after the clothing was removed from the contaminated environment. Compression of thick outerwear released additional vapor. Mean times to reach 0 ranged from 7 minutes for jeans to 42 minutes for down jackets. Conclusions:, This simulation model of chemical vapor release demonstrates persistent presence of simulant vapor over time. This implies that chemical vapor may be released from the victims' clothing after they are evacuated from the site of exposure, resulting in additional exposure of victims and emergency responders. Insulated outerwear can release additional vapor when handled. If a patient has just moved to a vapor screening point, immediate assessment before additional vapor can be released from the clothing can lead to a false-negative assessment of contamination. [source] Analysis of Soil Vapor Extraction Data to Evaluate Mass-Transfer Constraints and Estimate Source-Zone Mass FluxGROUND WATER MONITORING & REMEDIATION, Issue 3 2010Mark L. Brusseau Methods are developed to use data collected during cyclic operation of soil vapor extraction (SVE) systems to help characterize the magnitudes and time scales of mass flux associated with vadose zone contaminant sources. Operational data collected at the Department of Energy's Hanford site are used to illustrate the use of such data. An analysis was conducted of carbon tetrachloride vapor concentrations collected during and between SVE operations. The objective of the analysis was to evaluate changes in concentrations measured during periods of operation and nonoperation of SVE, with a focus on quantifying temporal dynamics of the vadose zone contaminant mass flux, and associated source strength. Three mass flux terms, representing mass flux during the initial period of an SVE cycle, during the asymptotic period of a cycle, and during the rebound period, were calculated and compared. It was shown that it is possible to use the data to estimate time frames for effective operation of an SVE system if a sufficient set of historical cyclic operational data exists. This information could then be used to help evaluate changes in SVE operations, including system closure. The mass flux data would also be useful for risk assessments of the impact of vadose zone sources on groundwater contamination or vapor intrusion. [source] Results of a Proposed Breath Alcohol Proficiency Test ProgramJOURNAL OF FORENSIC SCIENCES, Issue 1 2006Rod G. Gullberg M.P.A. ABSTRACT: Although proficiency test programs have long been used in both clinical and forensic laboratories, they have not found uniform application in forensic breath alcohol programs. An initial effort to develop a proficiency test program appropriate to forensic breath alcohol analysis is described herein. A total of 11 jurisdictions participated in which 27 modern instruments were evaluated. Five wet bath simulator solutions with ethanol vapor concentrations ranging from 0.0254 to 0.2659 g/210 L were sent to participating programs, instructing them to perform n=10 measurements on each solution using the same instrument. Four of the solutions contained ethanol only and one contained ethanol mixed with acetone. The systematic errors for all instruments ranged from ,11.3% to +11.4% while the coefficient of variations ranged from zero to 6.1%. A components-of-variance analysis revealed at least 79% of the total variance as being due to the between-instrument component for all concentrations. Improving proficiency test program development should consider: (1) clear protocol instructions, (2) frequency of proficiency testing, (3) use lower concentrations for determining limits-of-detection and -quantitation, etc. Despite the lack of a biological component, proficiency test participation should enhance the credibility of forensic breath test programs. [source] Establishing ignition conditions for the tank manifold fire at the Powell Duffryn tank terminalPROCESS SAFETY PROGRESS, Issue 3 2002John L. Woodward A fire destroyed three tanks containing crude sulfate turpentine (CST) at a storage facility in Savannah, Georgia, on April 10, 1995, prompting an evacuation, and resulting in some environmental damage. The events of this fire have been documented an a U.S. EPA report [1]. The investigators determined the most likely cause of ignition was overheating in a newly-installed activated-carbon drum as air was drawn in during evening cooling. One aspect not entirely explained in the EPA report is that the tanks were connected by a vapor manifold and were not protected by detonation arresters, yet the flames initially propagated to only one tank. This paper discusses the development of a model to quantify the likely sequence of events that is consistent with observations. Tank inflows and outflows forced by the diurnal temperature cycle were modeled to calculate hydrocarbon concentrations in the vapor space. This establishes that the combination of vapor concentrations above the lower flammable limit, and oxygen concentrations above the lower limit to support combustion, occur for only a few hours during the day. Further estimates of the ignition, flame acceleration, and run-up distance indicate that an explosion probably occurred inside the polyvinyl chloride (PVC) pipe. The forces from such an explosion would be sufficient to open the PVC pipe, thereby slowing the flame front propagation and contributing to the failure to initially ignite more than one tank. This paper illustrates how modeling strengthens an accident investigation and helps distinguish between alternative postulated ignition sequences. [source] | |||||||||||||