Donald H Stedman
In memory of

Donald H Stedman
University of Denver · Department of Chemistry and Biochemistry

PhD

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260
Publications
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Publications

Publications (260)
Article
State and local agencies in the United States use activity-based computer models to estimate mobile source emissions for inventories. These models generally assume that vehicle activity levels are uniform across all of the vehicle emission level classifications using the same age-adjusted travel fractions. Recent fuel-specific emission measurements...
Article
Repeated, fuel-specific, emission measurements in Denver (2005/2013), Los Angeles (LA) (2008/2013), and Tulsa (2005/2013) provide long-term trends in on-road reactive nitrogen emissions from three light-/medium-duty U.S. fleets. Reductions in oxides of nitrogen (NOx) emissions ranged from 21% in Denver (from 5.6 ± 1.3 to 4.4 ± 0.2 g of NOx/kg of fu...
Article
The introduction of particulate and oxides of nitrogen (NOx) after-treatment controls on heavy-duty vehicles has spurred the need for fleet emissions data to monitor their reliability and effectiveness. The University of Denver has developed a new method for rapidly measuring heavy-duty vehicles for gaseous and particulate fuel specific emissions....
Article
The global economic recession of 2008-2010 severely depressed light-duty vehicle sales in the United States. On-road fleets observed with a remote vehicle exhaust sensor in 2013 at three historical sampling locations in Denver, Los Angeles, and Tulsa showed large reductions in the fleet fractions of 2009 model year vehicles of 40%, 38%, and 35%, re...
Article
A new on road heavy-duty diesel vehicles (HDDV) Monitoring System (OHMS) system for the determination of heavy duty diesel vehicle emissions is presented. The system integrates the exhaust emissions over about an8 sec acceleration cycle, including gear changes, and provides results for fuel-based particulate number, mass and black carbon emissions,...
Article
California and Federal emissions regulations for 2007 and newer heavy-duty diesel engines require an order of magnitude reduction in particulate matter and oxides of nitrogen spurring the introduction of new aftertreatment systems. Since 2008, four emission measurement campaigns have been conducted at a Port of Los Angeles location and an inland we...
Article
Unlabelled: As part of the 2010 Van Nuys tunnel study, researchers from the University of Denver measured on-road fuel-specific light-duty vehicle emissions from nearly 13,000 vehicles on Sherman Way (0.4 miles west of the tunnel) in Van Nuys, California, with its multispecies Fuel Efficiency Automobile Test (FEAT) remote sensor a week ahead of th...
Article
Unlabelled: The Desert Research Institute conducted an on-road mobile source emission study at a traffic tunnel in Van Nuys, California, in August 2010 to measure fleet-averaged, fuel-based emission factors. The study also included remote sensing device (RSD) measurements by the University of Denver of 13,000 vehicles near the tunnel. The tunnel a...
Article
Recent U.S. Environmental Protection Agency emissions regulations have resulted in lower emissions of particulate matter and oxides of nitrogen from heavy-duty diesel trucks. To accelerate fleet turnover the State of California in 2008 along with the Ports of Los Angeles and Long Beach (San Pedro Bay Ports) in 2006 passed regulations establishing t...
Article
The three California cities of San Jose, Fresno, and West Los Angeles (wLA) were visited during March 2008 to collect on-road emission measurements of reactive nitrogen compounds from light-duty vehicles. At the San Jose and wLA sites, comparison with historical measurements showed that emissions of carbon monoxide (CO), hydrocarbons (HC), and nitr...
Article
As part of the National Park Service's Temporary Winter Use Plans Environmental Assessment, the University of Denver has been collecting in-use tailpipe emissions data from snowcoaches and snowmobiles in Yellowstone National Park. During the winter of 2006, using a portable emissions monitoring system, tailpipe data were collected from 10 snowcoach...
Conference Paper
The traditional on-road emissions remote sensing technique has been enhanced with the ability to monitor not only CO, CO2, HC and NO, but also SO2, NH3 and NO2. Modern diesel powered vehicles, particularly in Japan and Europe are equipped with diesel particle filters (DPFs). These traps are frequently designed to be self regenerating by means of a...
Article
A multiyear, on-road emission measurement program carried out in the cities of Chicago, Illinois; Denver, Colorado; Los Angeles (LA), California; and Phoenix, Arizona shows large, fuel-specific tailpipe emissions reductions at all of the sites for carbon monoxide (CO), hydrocarbons (HC), and nitric oxide (NO). CO emissions decreased between 56% (De...
Article
On-road measurements in 2005 of carbon monoxide (CO), hydrocarbons, nitric oxide, nitrogen dioxide, and sulfur dioxide from 1641 individually identified heavy-duty diesel trucks at two locations in Colorado are reported. Carbon monoxide and nitric oxide show increasing emissions with increased altitude. Oxides of nitrogen (NOx) emissions have decre...
Article
Full-text available
This study reports the largest data set of on-road, fuel-based mass emissions of ammonia and sulfur dioxide from vehicles of known make, model year, and fuel type. Ammonia is the first pollutant observed for which the emissions decrease with increasing fleet age from 10 to 20 years. The fixed nitrogen emission ratio is 15.0% by mass and 24.7% by mo...
Article
—Homocarnosine, rather than carnosine, is the major imidazole dipeptide present in human CSF. This compound can be readily detected in the CSF of normal infants and young children, while it is either not detectable or is present only in very small concentrations in the CSF of normal adult subjects. Slightly greater amounts of homocarnosine can be f...
Article
Full-text available
The application of Remote Sensing Device (RSD) for the measurement of on-road mobile source emissions from the vehicles driving on the roads, was described. Commercial RSD units use a non-dispersive infrared (NDIR) sensor equipped with a band pass interference filter corresponding to the C-H stretching region around 2970 cm -1 to measure the mobile...
Article
Against a backdrop of lawsuits, a new study shows that reductions in snowmobile emissions highlight the need for snowcoach fleet to modernise.
Article
The 1990 Clean Air Act amendments require the U.S. Environmental Protection Agency (EPA) to set guidelines for states to follow in designing and running vehicle inspection and maintenance (I/M) programs. Included in this charge was a requirement to implement an on‐board diagnostic (OBD) test for both basic and enhanced I/M programs. This paper prov...
Article
Full-text available
The chemiluminescence spectra from the reaction of ozone with nickel tetracarbonyl, iron pentacarbonyl, dicobalt octacarbonyl, and cobalt tricarbonyl nitrosyl in excess carbon monoxide were investigated. The use of Ocean optics' new QE65000 high quantum efficiecy spectrometer provided relative spectral intensities for these reactions. The reaction...
Article
Full-text available
A remote sensor for measuring on-road vehicles passing the sensor in real time is described. This sensor expands upon previous technology that measured carbon monoxide, carbon dioxide, and exhaust hydrocarbons in the IR and nitric oxide in the UV. The design adds the capability to measure nitrogen dioxide in the UV with one spectrometer and to meas...
Article
Full-text available
In order to inform policy and increase understanding of air pollution effects, there is a requirement for more information on the emissions of New Zealand's vehicle fleet. The remote sensing campaign was implemented to establish the emissions profile for the on-road vehicle fleet. The data have been used to investigate the important factors that de...
Article
In 1993, on-road emissions in Continental Europe showed a pronounced South/North declining gradient for CO, HC and NO fuel specific emissions (gm/kg). Emissions in Hamburg and Rotterdam were comparable to emissions measured in 1993 in the U.S.A. with the same on-road instrument. Contrasts between emissions in the USA, the UK and Sweden demonstrated...
Article
Remote sensing of light duty vehicle on-road tailpipe exhaust has been used to measure on-road mass emissions of automobile fleets in Denver for 13 years and in two other U.S. cities for 5 years. Analysis of these fleets shows that newer automobiles, during a period of fairly constant new car standards, have become continually less polluting indepe...
Article
An earlier analysis of the inspection and maintenance (I/M) program in Phoenix, Arizona [Environ. Sci. Policy 4 (2001) 377] found that fleet average emissions increased or “deteriorated” substantially between biennial I/M test cycles, and that a large fraction of the vehicles that initially failed and later passed in the first I/M cycle failed agai...
Article
Opacity measurements were taken for three light-duty diesel vehicles (a Ford Club van, an Isuzu pickup, and a 2000 Ford F250 pickup) using on-road remote sensors in Denver, CO, in February 2001. Visible opacity under steady-state driving conditions was rare for these vehicles. For the first day of testing, the Isuzu pickup and the Ford F250 with th...
Article
A new design of a motor vehicle emissions remote sensor was developed with a single lead selenide detector and multiple rotating filters. This device measured CO/CO2 and hydrocarbon (HC)/CO2 ratios from passing cars in a single lane. The single detector system, while also reducing instrument cost, required only a single gas calibration upon setup f...
Article
Emission inventories from mobile sources have traditionally been obtained through computational modeling. This method, however, has intrinsic shortcomings in that the factors used incorporate only a limited amount of real-world observations. The agreement between model predictions and measurements has often been poor. Recently, a fuel-based method...
Article
Remote sensing nitric oxide (NO) measurements are difficult to analyze because load varies among on-road vehicles measured by remote sensing and NO emissions are dependent on load. Remote sensing NO measurements were made on passenger cars in 1997, 1998, and 1999 in Chicago, IL at a site where few vehicles had loads greater than those encountered i...
Article
Increases in the number of winter visitors to Yellowstone National Park during the past decade have raised concerns over the environmental impacts of snowmobiling in the park. During the 1998-99 season, more than 62,000 snowmobile and 1300 snow coach trips entered the park. Using the University of Denver's vehicle exhaust remote-sensing equipment,...
Article
On-road measurements of carbon monoxide, hydrocarbons, and nitric oxide from 5772 heavy-duty diesel trucks at five locations in the United States and Europe show slightly increasing emissions with increasing altitude. The result for nitric oxide showed a statistically significant increase of 4.1 +/- 1 gNO/kg of fuel consumed/km increase in altitude...
Article
Emission inventories from mobile sources have traditionally been obtained through computer modeling. This method, however, has intrinsic shortcomings in that ideal factors are included while real-world observations are left out. The model predictions have not correlated well with measurements from several studies. Recently, a fuel-based method of o...
Article
this report are those of the authors and may not necessarily
Article
Using input from the public, a new type of vehicle emissions information system has been developed which utilizes an innovative variable message sign to display individual vehicle emissions information to passing drivers. Called the Smart Sign, the system merged highway messaging and on-road vehicle emissions sensing into a cost-effective public in...
Article
Using open-path Fourier transform infrared spectroscopy (OP-FTIR) we have measured the variations in ambient concentrations of carbon monoxide (CO), carbon dioxide (CO2), and nitrous oxide (N2O) caused by emissions from motor vehicles at a high traffic site in the Denver metropolitan area. Comparison of the OP-FTIR data to average emissions results...
Article
The University of Denver (DU) has developed a new remote sensor for the measurement of mobile source nitric oxide (NO). This system is integrated with an existing infrared remote sensor and is capable of measuring carbon monoxide and hydrocarbons in addition to NO, at a rate of more than 1000 vehicles/hr. The detection limit on a low-emitting vehic...
Article
Snowmobiles (sleds) have become a very popular way for visitors to explore Yellowstone National Park during its winter season with more than 60 000 visits during the 1997−1998 season. In-use emissions data are very limited, and only a small number of sleds tested under controlled conditions have had their measurements reported. Snowmobiles are curr...
Article
Automobile emissions are the major urban source of carbon monoxide, and they are also important globally. One estimate by the Japanese Automobile Research Institute (JARI) of the 1990 global CO emissions from automobiles is 231 megatonnes (Mt). The same source gives the USA 1990 emissions as 21 Mt, whereas the US Environmental Protection Agency (EP...
Article
Worldwide increases in commercial air traffic have raised concerns about the effects of aircraft emissions on the atmosphere. The purpose of this study was to demonstrate the capability of a remote sensor, developed for the measurement of automobile emissions, in measuring nitric oxide emission indices from in-use aircraft on the ground without int...
Article
On-Road Remote Sensing of Automobile Emissions in the Phoenix Area: Year 3 1 EXECUTIVE SUMMARY The University of Denver conducted a five-day remote sensing study in the Phoenix, AZ area in the fall of 2000. The remote sensor used in this study is capable of measuring the ratios of CO, HC, and NO to CO 2 in motor vehicle exhaust. From these ratios,...
Article
On-road remote sensing measurements of vehicle carbon monoxide (CO) emissions in Denver, CO, have discovered vehicles that, after failing a state inspection and maintenance (I/M) test, are avoiding repair through sales to individuals who register them outside the program but still drive the vehicles in the I/M area. This reduces the emissions benef...
Article
In 1991, the nation of Mexico lowered light-duty vehicle emission standards leading to the introduction of catalytic convertors. On-road emissions were measured in Monterrey, Nuevo Léon, Mexico in 1995 from more than 24 000 vehicles. The Subsecretaría de Ecología's Office was able to provide vehicle registration information for 10 654 vehicles. The...
Article
In January 1995, the State of Colorado superseded an annual decentralized idle test program with an EPA recom mended biennial centralized IM240 test program in the six-county metro Denver area. Odd model year 1982−1994 vehicles and any vehicles that entered the counties or changed ownership required testing in 1995. Even model year vehicles were to...
Article
Here, in situ sensing of the emissions from motor vehicles is reviewed. The role of thermodynamics, chemical reaction kinetics, stoichiometry of reactions, heat transfer, and fluid flow are considered. 27 refs., 5 figs.
Article
Full-text available
In return for a temporary waiver from converting five vehicles to operate on compressed natural gas (CNG) for the Denver Clean Fuels program, the University of Denver identified, tested, repaired, and retested nine employee commuter vehicles. The results of the study validated the concept that employer-based identification and repair programs can b...
Article
Test-to-test variability has been observed by many current testing methods, including the Federal Test Procedure, the IM240 dynamometer test, the idle test common to many Inspection and Maintenance programs, and on-road remote sensing. The variability is attributable to the vehicle, not to the testing procedure. Because the vehicles are the dominan...
Article
Motor vehicle emission rates of CO, NO, NOx, and gas-phase speciated nonmethane hydrocarbons (NMHC) and carbonyl compounds were measured in 1992 in the Fort McHenry Tunnel under Baltimore Harbor and in the Tuscarora Mountain Tunnel of the Pennsylvania Turnpike, for comparison with emission-model predictions and for calculation of the reactivity of...
Article
Experiments were conducted in the Fort McHenry Tunnel in Baltimore, MD, and in the Tuscarora Mountain Tunnel in Pennsylvania, during the summer of 1992 to evaluate real-world automotive emissions. Included in these experiments were the first reported measurements of individual vehicle exhaust in tunnels by a remote sensing device (RSD). Results are...
Article
This study presents an evaluation of inspection and maintenance (I/M) programs in terms of their effect on motor vehicle carbon monoxide (CO) and hydrocarbon (HC) exhaust emissions as measured on-road by remote sensing technology. The results show that the performance of past I/M programs at several monitored locations has been less effective than...
Article
Full-text available
Inspection and maintenance programs for motor vehicles in the United States increasingly use loaded mode mass emissions testing (IM240). A method was developed to predict mass emission rates and mass emission changes, particularly from repair benefits, using a low-cost, portable four-gas non- dispersive infrared (NDIR) vehicle exhaust gas analyzer....
Article
A nitric oxide (NO) detector was developed and integrated into the original carbon monoxide (GO) and hydrocarbon (HC) remote sensing System developed by the University of Denver. The system is capable of measuring the CO, HC, and NO exhaust emissions of thousands of on-road vehicles per day. Analysis of a typical field measurement in Denver shows C...
Article
The United States Environmental Protect ion Agency (EPA) computer model of mobile source emissions is used to estimate the benefits of future emissions control programs. Four input assumptions are discussed, each of which tends to overestimate the benefits of biennial testing programs. The assumptions are: each model year drives the same number of...
Article
The remote sensing technology developed by the University of Denver provides the first practical approach to routinely characterize real-world, on-road automobile CO and HC exhaust emissions. It has been used to measure the exhaust emissions of more than 1 000 000 vehicles in many locations, This study presents an analysis and comparison of 22 flee...
Article
Atmospheric RO(x) radicals (HO + HO2 + RO + RO(2)) were measured for 1 month in the summer of 1993 in Denver, CO. The results are correlated with solar UV fluxes and ozone mixing ratios monitored during the same period. The RO(x) radical measurements were also compared to predictions from a simple computer simulation. Significant free radical level...
Article
The fluxes of nitrogen dioxide and ozone, as well as supporting meteorological data, have been measured at a snow covered grassland field site in northern Colorado by eddy correlation. The fluxes of both species are small. The median surface resistance to ozone deposition is greatest during the morning and least during the afternoon. The nitrogen d...
Article
In 1990 Congress passed the Clean Air Act Ammendments, many parts of which deal with motor vehicles. Motor vehicles are the primary source of urban carbon monoxide and are an important source of hydrocarbons and oxides of nitrogen responsible for the formation of photochemical smog and ground-level ozone. Cost estimates for implementing the Acts`s...
Article
A new remote sensor for measuring on‐road carbon monoxide, carbon dioxide, and hydrocarbon exhaust emissions in under 1 s from vehicles passing the sensor is described. The new design adds the capability for measuring exhaust hydrocarbons and eliminates the need for liquid–nitrogen‐cooled detectors while improving upon the overall signal to noise....
Article
An improved chemical amplifier for atmospheric RO(x) (HO + HO2 + RO + RO(2)) radical measurement is reported. The reaction chamber in this version was equipped with a Teflon filter-nitrogen wall to maintain the nature of the wall constant and reduce the free radical wall loss. The results of laboratory studies were consistent with theoretical calcu...
Article
The sulfur chemiluminescence detector (SCD) is a sensitive, highly selective sulfur detection system based on reaction in hydrogen/air combustion followed by extraction and low-pressure chemiluminescence. This report documents investigations into the fundamental chemical processes occurring in the SCD. The conclusion from this work is that ozone re...
Article
A technique is described for low parts-per-trillion (ppt) detection of SO2 with high temporal resolution compared to current filter sampling methods. A sulfur chemiluminescence detector, equipped with a quartz burner chamber and a sample probe with a critical orifice, was used as a single detector to analyze SO2 in ambient air by alternately cyclin...
Article
In the present study, we investigated the statistical distributions of on-road CO and HC emissions by comparing the askewness and kurtosis of the distributions. The results of the analysis based on remote sensing data sets show that on-road automobile CO and HC emission distributions are well represented by a [gamma]-distribution. Laboratory dynamo...
Article
We have a device capable of remotely monitoring the mass emissions of CO and HC from passing vehicles in gm/l of fuel used in under 1 s/vehicle. The results from measuring the emissions of over 200 000 vehicles using this device show that a few vehicles, typically less than 10% of the fleet, are responsible for half the total emissions. This 10% of...
Article
Full-text available
An intercomparison study was conducted between two instrumented vehicles and a new nitrogen oxide (NO) remote sensor developed by the University of Denver. A 1992 Aerostar minivan and a 1991 Taurus wagon were equipped with on-board engine control and monitoring systems, as well as instrumentation for measuring the vehicle exhaust emissions in real...
Article
The University of Denver used its remote sensor for motor vehicle CO and HC emissions to measure the tailpipe concentrations of over 90,000 California Vehicles in a 30-day period in 1991. The study consisted of three phases; a series of controlled tests, a pullover study of high-emitters, and a series of measurements at a variety of sites around th...
Article
The University of Denver’s remote sensing system for vehicle exhaust has been successfully adapted to the measurement of vehicle emissions in a tunnel environment. Two studies conducted at the Fort McHenry Tunnel in Baltimore, MD and the Tuscarora Mountain Tunnel located west of Harrisburg, PA on the Pennsylvania Turnpike are described. The difficu...
Article
The University of Denver's remote sensor for on-road motor vehicle carbon monoxide (CO) and hydrocarbon (HC) emissions was used in August and October, 1991, at two different locations in the Denver area. The results of analysis for HC emissions show a similar skewed distribution for the two data sets, although the average HC emissions are very diff...
Article
Full-text available
The fluxes of NOâ, NO{sub y}, and ozone were measured by eddy correlation at a grassland field site from March 5 to August 2, 1988. The nitrogen oxide fluxes were generally small and upward during the day. Overnight, the fluxes were zero. The average daytime NOâ flux increased from 2.2 ng (N) m⁻²s⁻¹ during March and April (Julian days 65 to 1...
Article
The cost-effectiveness of identification and repair of vehicles with excessive carbon monoxide emissions was investigated over the 1991 -92 winter period in Provo, Utah. This pilot program used on-road remote sensing at two locations to identify repeat gross polluting vehicles. The owners of gross polluters observed at one of the locations were sol...
Article
The University of Denver remote sensor for automobile exhaust was set up for nine days at five locations in the Mexico City area. A total of 31,838 valid readings for CO and HC emissions were obtained. The emissions distribution was unlike any other we have observed in North America or Europe, in that the emissions for both CO and HC were vastly gr...
Article
The photolysis frequency of ozone to singlet D oxygen atoms has been measured by means of a chemical actinometer using a luminol based detector. The instrument measures j(O3-O(1D)) with a precision of 10 percent. The data collected in winter and spring of 1991 is in agreement with model predictions and previously measured values. Data from a global...
Article
The ground-level photolysis frequency of ozone J(O3) to produce metastable singlet D oxygen atoms (O (D-1)) is measured using a novel instrumental technique involving electrical conductivity. The O(D-1) atoms produced react with nitrous oxide (N2O) carrier gas to form higher oxides of nitrogen (NO(x)). These oxides were detected by mixing with meth...
Article
With initial support from the Colorado Office of Energy Conservation in 1987, the University of Denver (DU) developed an infra-red (IR) remote monitoring system. In less than a second the instrument measures the carbon monoxide to carbon dioxide ratio (CO/COâ) in the exhaust of most vehicles passing through the IR light beam. It has been shown to g...
Article
Full-text available
Spectroscopic and solubility studies of reaction products of soot (black carbon) with O3, NO2/N2O4, and SO2 have revealed a relationship between reactivity and product solubility and structure. A remarkably high solubility of ozonated n-hexane soot has its origin in the formation of anhydride and lactone surface structures and their subsequent hydr...
Article
Carbon monoxide (CO) emission measurements of thousands of vehicles per day are possible with a recently evaluated remote sensor (Fuel Efficiency Automobile Test) developed at the University of Denver. Funded by the Environmental Monitoring Systems Laboratory - Las Vegas (EMSL-LV) Innovative Research Program, the evaluation has demonstrated the com...
Article
A device and method are described for measuring the concentrations of components of a fluid stream. Preferably, the fluid stream is an in-situ gas stream, such as a fossil fuel fired flue gas in a smoke stack. The measurements are determined from the intensity of radiation over a selected range of radiation wavelengths using peak-to-trough calculat...
Article
A field evaluation of the sulfur chemiluminescence detector (SCD) as a real-time total atmospheric sulfur detector is presented. The SCD was installed in a monitoring trailer along with a flame photometric detector (FPD), fluorescent SO{sub 2} monitor (Fluor), and a suite of other monitoring instruments. The performance of the analyzers was compare...
Article
As part of a major filed 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...
Article
The University of Denver's remote sensor for carbon monoxide has been used to perform a study of CO emissions from in-use vehicles during the State of Colorado's 1988-1989 Oxygenated Fuels program. More than 117,000 vehicle exhaust measurements were performed on warm vehicles at two locations in the Denver area, with more than 4,900 vehicles identi...
Chapter
Full-text available
The fluxes of nitrogen oxides and ozone have been measured over the prairie grassland of Northern Colorado by eddy correlation. The deposition velocity of ozone varied diurnally. The ozone maximum deposition velocity occurred at around midday, Vd = 0.4 cm s-1, and was zero overnight. The net flux of nitrogen oxides was upward, with a diurnal and a...
Article
An approximate equation is developed relating carbon monoxide (CO) hourly observed concentrations to an averaged hourly emission inventory. The equation is used to investigate the effect on CO levels at a particular monitoring station of allowing Denver to remain on Daylight Savings Time (DST) for the entire year. The equation converts hourly CO va...
Article
The authors undertook a new approach using an old technology to develop a long-path IR photometer that can remotely measure CO emissions from operating vehicles. The University of Denver's instrument consists of three basic units: the source, a detector, and a computer. IR absorption is used to determine the amounts of CO and CO2 emitted by a passi...
Article
A universal sulfur detector (USD) capable of measuring both reduced and oxidized sulfur compounds in the low picogram range is described. Products of a hydrogen flame are drawn through a critical orifice into a low-pressure flow system and then mixed with ozone. Sulfur compounds entering the flame produce sulfur monoxide which undergoes a chemilumi...