Accuracy Assessment of EPA Protocol Gases Purchased In 1991

ABSTRACT

Fixed-roof tanks are used extensively at manufacturing, waste management, and other facilities to store or process liquids containing volatile organic compounds. Federal and state air standards require the control of organic air emissions from many of these tanks. A common practice used for some fixed-roof tanks that are required to use controls is to vent the tank through an activated carbon canister. When organic vapors are adsorbed on activated carbon, heat is released. Under certain conditions, the temperature of the carbon bed can increase to a level at which the carbon or organic vapors spontaneously ignite, starting a fire in the carbon bed. Bed fires in carbon canisters are not uncommon and can present a significant safety hazard at facilities if proper safety measures are not implemented. This article discusses how carbon adsorber bed fires occur and presents general guidance on safety measures for carbon canisters installed on fixed-roof tanks to reduce the likelihood of a carbon bed fire and to minimize the impact in the event of a fire.     

Evaluation of Parts-per-billion Organic Cylinder Gases for Use as Audits During Hazardous Waste Trial Burn Tests

A repository of 14 gaseous organic compounds at parts-per-billion levels (7-430 ppb) in compressed gas cylinders has been established by the Environmental Protection Agency. This repository was established to provide audit materials for use in conducting performance audits to assess the accuracy and precision of principal organic hazardous constituent (POHC) measurements, especially those performed during hazardous waste trial burn tests. Five- and nine-component mixtures In a balance gas of nitrogen were prepared in aluminum cylinders for use in the performance audit program. The five-component mixtures contain carbon tetrachloride, chloroform, perchloroethylene, vinyl chloride, and benzene. The ninecomponent mixtures contain trichloroethylene, 1,2-dichloroethane, 1,2-dibromoethane, acetonitrile, trichlorofjuoromethane, dichlorodifluoromethane, bromomethane, methyl ethyl ketone and 1,1,1-trichloroethane.

Studies of all 14 gaseous organic compounds were performed to determine the stability of the compounds and the feasibility of using them in performance audits. Results indicate that ail of the 14 compounds were adequately stable to be used as reliable audit materials. Also, the estimation of specific uncertainties associated with the analysis of these audit materials and how those uncertainties are used to assign a total uncertainty to the final analyte concentration for 14 organics Is described.

Subsequent to completion of the stability studies, several performance audits were conducted using the repository gases to assess the accuracy and precision of the volatile organic sampling train (VOST) and bag measurement methods. The audit results indicate that laboratories can use these methods to analyze POHC with accuracy usually to within ± 50 percent of the audit concentrations.     

Inspection and Maintenance for Reducing Automobile Emissions

EPA has recently evaluated several inspection and maintenance approaches for in-use vehicles that are potentially applicable to pre-1975 automobiles. The results of this evaluation are described and used to estimate the effecliveness and cost of inspection/maintenance for reducing total automobile emissions through 1985. It is estimated that inspection/maintenance programs for pre-1975 automobiles may be capable of achieving eight and ten percent reductions in total automobile emissions of HC and CO respectively until 1980 and two to three percent reductions in 1985. The need for inspection of automobiles of model year 1975 and later, and the potential applicability of present short-duration inspection procedures to these vehicles, are also discussed.     

Evaluation of Selected Gaseous Halocarbons for Use in source Test Performance Audits

A repository of 38 gaseous organic compounds in compressed gas cylinders has been established by EPA. This repository was established to provide standards for source test performance audits, that is, quantitative quality assurance tests. Among these compounds are ten halogenated organic species, which are the focus of this paper.

Stability studies of all ten compounds have been performed to determine the feasibility of using them as performance audit standards. Results indicate that all of the halocarbons tested are adequately stable to be used as reliable audit standards.

Subsequent to completion of stability studies, four of the ten halocarbons were used in source test performance audits. Results are available at this time for two of the four compounds; the results show agreement within 10% of the concentrations previously established by Research Triangle Institute.     

An Investigation of Idle Emissions Inspection and Maintenance at Altitude

Idle emissions inspection and maintenance was evaluated using a sample of 300 privately owned 1964 through 1973 model-year vehicles operating in the Denver metropolitan area. Ten privately owned stations, licensed by the State of Colorado to perform vehicle safety inspections, were utilized to conduct idle emissions inspection and subsequent maintenance of failed vehicles. Exhaust hydrocarbon (HC) and carbon monoxide (CO) reduction as measured by the 1975 Environmental Protection Agency (EPA) mass emission testing procedures was indicated to be 13% and 8% respectively at a 50 % rejection rate. The average maintenance cost to achieve the reduction was $11.32 per failed vehicle.

The adjustment and repair procedures provided to participating garages were sufficient to achieve significant emissions reduction and training provided to garage personnel was adequate. However, several problems were experienced with station personnel relative to data transmittal and inspection pass/fail limits. Problems were also experienced with respect to correlations between laboratory and garage-type analytical instrumentation.     

Modeling In-Use Vehicle Emissions and the Effects of Inspection and Maintenance Programs

Different ways for modeling the impact of vehicle emission inspection and maintenance programs on fleet hydrocarbon emissions are examined. A dynamic model is developed for forecasting fleet emissions in which individual vehicle performance is modeled as a stochastic process and vehicle emissions are tracked over time. Emissions inspection and repair are incorporated into the model, allowing for the stochastic aspects of both testing and repair. This model is compared to EPA’s model for evaluating the impact of vehicle emissions inspection and maintenance. We find that the way vehicle emission equipment deterioration overtime is modeled is important for forecasting emissions from the fleet and for assessing the success of inspection and maintenance programs. For inspection programs, we find that factors such as the proportion of vehicles tested, and repair effectiveness and duration have the greatest impact on emission reductions. The ability of different emission testing regimes to identify polluting vehicles has less impact on a program’s overall potential for emissions reduction. Policy recommendations for I&M testing and predictions of emission reduction credits from these tests will depend in important ways on the methods used in the underlying emissions models.     

The Clean Air Act Amendments and Motor Vehicle Inspection/Maintenance

Seventeen days of detailed measurements of NO, NO₂, O₃, HNO₃ and the frequency of NO₂ photolysis—j(NO₂)—were carried out in Claremont, CA, in September 1980. Under conditions when the rate of change of NO concentration is small, there must be a balance between formation and loss processes. In the classical photostationary state this balance is between NO₂ photolysis: NO₂ + hv → NO + O and reaction with ozone: NO + O₃ → NO₂ + O₂. The results show that the latter reaction with ozone is inadequate to balance the formation step; a significant contribution is required from another NO oxidation process, possibly peroxy radical oxidation. If so, the inferred concentration of peroxy radicals shows a diurnal variation, peaking around solar noon.     

Performance and Problems of Claus Plant Operation on Coke Oven Acid Gases

The application of Claus Plant sulfur recovery units to the coke oven gas (COG) acid gases at three Bethlehem Steel Corporation plants is discussed. While many of the problems encountered are not unique to coke oven gas-derived acid gases, it was found that special consideration must be given to the effect of components not normally encountered in the typical Claus plant application to petroleum derived gases. It is perhaps fortunate that the feed composition to the three units was sufficiently different to expedite recognition of the source of some of these difficulties. One substance of concern is the hydrogen cyanide normally found in COG acid gases. In the absence of some means of removing or decomposing this material before it enters the Claus Plant extensive corrosion within the unit is observed after a short period of time. This is due to the fact that, contrary to expectation, a substantial quantity of this material survives the burner flame. The various alternatives in its elimination are discussed. A second major contaminant in COG acid gases is particulate iron sulfide and iron cyanide. While the exact source of these materials is in doubt, there is little doubt that in the absence of their removal, inorganic blockages within the Claus Plant will occur. By properly accounting for the special properties of coke oven gas-derived acid gas we have recently achieved short term sulfur recovery efficiencies of 95% and higher.     

Evaluation of a Low-Cost Transient Mass Measurement System in Vehicle Inspection and Maintenance Testing: Results of a Gordon-Darby Study

Abstract

A study was performed at a Gordon-Darby centralized inspection and maintenance (I/M) test lane in Phoenix, AZ, in December 1999 for the purpose of evaluating the accuracy of production Vehicle Mass Analysis System (VMAS) equipment relative to standard IM240 equipment. Simultaneous transient mass measurements were made on random vehicles using VMAS and IM240 systems on two test lanes during regular I/M testing. Cumulative mass emissions for 846 valid tests were correlated using least-squares regression analysis. Correlation indices were >0.99 for both carbon monoxide (CO) and nitric oxide (NO) and 0.93 for hydrocarbon (HC), and the standard errors of regression were 1.38 g/mi, 0.123 g/mi, and 0.245 g/mi for CO, NO, and HC, respectively. These strong correlation results are reflected by high excess emission identification rates of 99.4% for CO, 99.3% for NO, and 94.5% for HC when applying final IM240 cut points with a <2% error of commission for all pollutants.     

Biofiltration Control of Hydrogen Sulfide 2. Kinetics,Biofilter Performance,and Maintenance

The kinetics of H₂S oxidation in a biofilter were evaluated and the reaction rates determined to be first-order at low concentrations (<200 ppm), zero-order at high concentrations (>400 ppm), and fractional-order in the intermediate concentration range for H₂S in the inlet waste gas. The overall performance of the biofilter system and changes in compost properties were investigated for 200 days of operation. The compost biofiiter showed good buffering capacities to variations in gas flow rate and pollutant (H₂S) loading impacts. Hydrogen sulfide removal efficiencies exceeding 99.9% were consistently observed. System acidification and sulfate accumulation were identified as inhibitors of required biological activity. Routine washing of the compost effectively mitigated these deficiencies. System upset was determined to be caused by compost dry-out or system overloading. Methods were developed to provide for recovery of contaminated filter material.     

Emissions from lit-use Motor Vehicles in Los Angeles: A Pilot Study of Remote Sensing and the Inspection and Maintenance Program

As part of a major field study to understand the causes of persistent, elevated carbon monoxide pollution episodes in Los Angeles, we performed a project to understand the emissions of vehicles in use. In this experiment, we assessed the accuracy of a remote sensing instrument designed to measure CO concentrations from vehicles as they were driven on the road. The remote sensor was shown to be accurate within ten percent of the directly measured tailpipe value. We performed a roadside inspection on 60 vehicles and demonstrated that the remote sensor could be used as an effective surveillance tool to identify high CO-emitting vehicles. We also compared the roadside data set to the biennial Smog Check (I/M) tests for the same vehicles, and observed that carbon monoxide and exhaust hydrocarbons from high emitters were much higher than when the vehicles received their routine inspection. Furthermore, for the high-emitting vehicles in this data set, the length of time since the biennial Smog Check had little influence on the cars’ emissions in the roadside inspection.     

Soil and Compost Filters of Malodorant Gases

Removing low concentrations of pollutant gases from air streams is difficult and expensive.^1,2 Removal techniques include water scrubbing (with and without permanganate, hypochlorite, or lime), burning, and sorption by activated charcoal. The shortcomings of these techniques are that they require fuel, maintenance, water, high capital costs, they pollute the wash water, and/or some concentrate only, rather than remove the offender.     

The New England Air Quality Forecasting Pilot Program: Development of an Evaluation Protocol and Performance Benchmark

Abstract

The National Oceanic and Atmospheric Administration recently sponsored the New England Forecasting Pilot Program to serve as a “test bed” for chemical forecasting by providing all of the elements of a National Air Quality Forecasting System, including the development and implementation of an evaluation protocol. This Pilot Program enlisted three regional-scale air quality models, serving as prototypes, to forecast ozone (O₃) concentrations across the northeastern United States during the summer of 2002. A suite of statistical metrics was identified as part of the protocol that facilitated evaluation of both discrete forecasts (observed versus modeled concentrations) and categorical forecasts (observed versus modeled exceedances/nonexceedances) for both the maximum 1-hr (125 ppb) and 8-hr (85 ppb) forecasts produced by each of the models. Implementation of the evaluation protocol took place during a 25-day period (August 5–29), utilizing hourly O₃ concentration data obtained from over 450 monitors from the U.S. Environment Protection Agency’s Air Quality System network.     

Accuracy and Precision of Home Radon Monitoring and the Effectiveness of EPA Monitoring Guidelines

EPA has provided guidelines to homeowners for monitoring and mitigating radon in the home. The effectiveness of these guidelines is dependent, in part, on the accuracy and precision of monitoring methods. This paper proposes a model for radon monitoring accuracy and precision based upon a review of the monitoring literature. The model is then used to quantify the extent of potential misclassification of homes by radon level from the application of EPA guidelines.

Short-term monitoring performed in the basement during winter produced conservative (higher than actual) radon estimates, on average. For homes with annual concentrations of 4 pCi/L, approximately 30 percent will still have short-term results under 4 pCi/L. Underestimation of radon levels is cut by 50 percent or more by the use of monitors on first floor and basement (confirmatory monitoring) as opposed to monitoring the basement alone (screening monitoring). However, following the screening/confirmatory monitoring sequence suggested by EPA increases underestimation at radon levels under 8 pCi/L. The model was found to be sensitive to a number of the assumptions made, and specific follow-up studies are suggested.     

Calibration and error analysis of multiwavelength telephotometers

In preparation for the EPA-VISTTA summer 1979 field program, 12 multiwavelength telephotometers were tested and calibrated. A standard light source was used in the calibration process, and the linearity of the instruments was checked using neutral density filters. Calibration of the telephotometers was performed before and after this experiment to determine individual instrument response and drift. Results of the calibration indicated that the instruments had an average inherent error of approximately 1 per cent when operating in the contrast (or ratio) mode. The degree of error is less if a correction is made. In the absolute radiance mode, the instrument was estimated to have an average inherent error of approximately 10 per cent.Results of two of the telephotometer comparisons performed during the VISTTA program are shown to illustrate the problems of target selection and inhomogeneity. A comparison of the extinction coefficients determined from the telephotometers and the scattering coefficients measured by nephelometers showed reasonable agreement for the first example.A more comprehensive, side-by-side comparison showed that results from the two telephotometers agreed within 2 per cent in the ratio mode. However, the uncertainty in the extinction coefficient is between 10 and 15 per cent. This uncertainty can be reduced by eliminating the low contrast cases.     

Operation and Maintenance of Fabric Filters

Operation and maintenance and performing correct system monitoring of fabric filters is discussed. The anticipation of future problems at the time of start-up and the necessity of maintaining correct records on the system to assist in later troubleshooting is stressed. When all is going well, the fabric filter requires little but routine maintenance on moving parts, which is usually well identified in the service manuals. Problems usually appear as excessive emissions, high pressure drop, or inadequate bag life. In order to find the cause of these problems, one must have maintained sufficient Information on the system to identify what changed and when. With this information, there are logical paths to follow to the proper solutions.     

Calibration and Certification of Audit Devices for Transmissometers

Abstract

Speciated fine particulate matter (PM_2.5) data collected as part of the Speciation Trends Network at four sites in the Midwest (Detroit, MI; Cincinnati, OH; Indianapolis, IN; and Northbrook, IL) and as part of the Interagency Monitoring of Protected Visual Environments program at the rural Bondville, IL, site were analyzed to understand sources contributing to organic carbon (OC) and PM_2.5 mass. Positive matrix factorization (PMF) was applied to available data collected from January 2002 through March 2005, and seven to nine factors were identified at each site. Common factors at all of the sites included mobile (gasoline)/secondary organic aerosols with high OC, diesel with a high elemental carbon/OC ratio (only at the urban sites), secondary sulfate, secondary nitrate, soil, and biomass burning. Identified industrial factors included copper smelting (North–brook, Indianapolis, and Bondville), steel/manufacturing with iron (Northbrook), industrial zinc (North–brook, Cincinnati, Indianapolis, and Detroit), metal plating with chromium and nickel (Detroit, Indianapolis, and Bondville), mixed industrial with copper and iron (Cincinnati), and limestone with calcium and iron (Bondville). PMF results, on average, accounted for 96% of the measured PM_2.5 mass at each site; residuals were consistently within tolerance (±3), and goodness–of–fit (Q) was acceptable. Potential source contribution function analysis helped identify regional and local impacts of the identified source types. Secondary sulfate and soil factors showed regional characteristics at each site, whereas industrial sources typically appeared to be locally influenced. These regional factors contributed approximately one third of the total PM_2.5 mass, on average, whereas local mobile and industrial sources contributed to the remaining mass. Mobile sources were a major contributor (55–76% at the urban sites) to OC mass, generally with at least twice as much mass from nondiesel sources as from diesel. Regional OC associated with secondary sulfate and soil was generally low.