Final Report: A Noncryogenic Tunable Diode Laser Monitor for On-Road Vehicle Emissions

EPA Contract Number: 68D00270
Title: A Noncryogenic Tunable Diode Laser Monitor for On-Road Vehicle Emissions
Investigators: Nelson, David D.
Small Business: Aerodyne Research Inc.
EPA Contact: Richards, April
Phase: II
Project Period: September 1, 2000 through September 1, 2002
Project Amount: $224,899
RFA: Small Business Innovation Research (SBIR) - Phase II (2000) Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , SBIR - Monitoring , Small Business Innovation Research (SBIR)


Emissions from automobiles and trucks are an important atmospheric source of CO, NO, and hydrocarbons. These emissions are significant causes of the persistent regional smog problem and there are strict federal emissions standards in place regulating these emissions. On-road vehicles also emit many other compounds that are deleterious to the environment and to human health. These include many potential or proven carcinogens, such as formaldehyde and benzene. Recently, several groups have reported that ammonia emissions from mobile sources are much higher than previously recognized1-8. Ammonia reacts rapidly in the atmosphere with nitric acid to form fine particulate matter, which is another health issue of great current concern.

Therefore, there is a pressing need for a technology that can measure mobile source emissions from in-use vehicles in the real world, both for research purposes and for the evaluation and enforcement of existing and forthcoming pollutant-emission standards. Aerodyne Research, Inc., believes that remote sensing of individual vehicles using mid-infrared solid-state lasers can accomplish this goal. Aerodyne Research, Inc., has proven in previous work9-11 that this is a highly sensitive and specific method that can be implemented with great success using cw lead salt diode lasers. Thousands of cars can be evaluated in a single day using this approach. However, the commercialization of an instrument based on the use of cw lead salt diode lasers is problematic because these lasers often have unstable operating characteristics that necessitate frequent adjustments by an expert operator. Moreover, cw lead salt lasers require a large supply of liquid nitrogen to operate. The first goal of this research project was to demonstrate the feasibility of removing these barriers to commercialization by substituting recently invented pulsed quantum cascade (QC) lasers for the traditional lead salt lasers. QC lasers are far more stable and do not require cryogenic cooling when operated in pulsed mode. The feasibility of this approach was demonstrated during Phase I. During Phase II, the goal was to design, construct, and test a prototype remote sensor based on QC laser technology and to begin the commercialization process for this technology.

Summary/Accomplishments (Outputs/Outcomes):

During Phase I of this project, Aerodyne Research, Inc., obtained its first QC laser and demonstrated that adequate detection sensitivities could be achieved using room temperature QC lasers operated in pulsed mode. This was accomplished by detecting ambient ammonia in a multipass cell and by detecting ammonia emitted directly from a passing vehicle in a remote sensing parking lot study. The strength of these results led to the Phase II award. During Phase II, a prototype QC laser-based remote sensor was designed and marketed to potential commercialization partners. The success of these commercialization efforts led to the design and construction of a more capable prototype than originally proposed.

After discussions with several interested parties, a commercialization agreement was reached with Environmental Systems Products (ESP) to develop this technology into a commercial remote sensing instrument. ESP's investment in this technology allowed Aerodyne Research, Inc., to take advantage of the U.S. Environmental Protection Agency's (EPA) Phase IIB Option, which provided further research and development funding. These additional resources were used to design and construct a four-laser remote sensing instrument rather than the two-laser instrument originally proposed. Aerodyne Research, Inc., has worked closely with ESP throughout this project.

The four-laser detailed design was one of the project's major accomplishments. This design included numerous software improvements, electronics modifications, laser specifications, and a detailed opto-mechanical design. The resulting design describes a unique instrument whose capabilities are novel.

The next major accomplishment of this project was the actual construction of the prototype instrument. This task was accomplished with nearly complete success. The only significant exception was that one of the four QC lasers did not arrive during the project. Therefore, testing of the prototype instrument was carried out with three lasers rather than the four that it is capable of simultaneously operating. The three lasers that were received were for CO2, NO, and NH3. Aerodyne Research, Inc., still expects to receive the fourth laser (a CO laser) from the manufacturer (Alpes Lasers).

The final major accomplishment was the demonstration of the instrument in a parking lot study at Aerodyne Research, Inc. The subject motor vehicles were volunteered by Aerodyne's staff. The weather was sunny and warm (~85°F). In most cases, the vehicle was driven through the sensor 5-10 times beginning from a cold start. Approximately 20 separate experiments were performed, mostly on unique vehicles, so nearly 20 vehicles were studied with more than 100 vehicle passes through the sensor. Emission indices for NO, N2O, and NH3 were measured. As expected, large ammonia emissions were observed for several vehicles. New vehicles did not seem to be cleaner than old vehicles with respect to their ammonia emissions in this small, preliminary study.


The purpose of this project was to design, construct, and demonstrate a remote sensing instrument for on-road vehicle emissions based on technology that could readily be commercialized. Aerodyne Research, Inc., has succeeded in accomplishing this goal. The technology employed is based on recently invented QC lasers. These lasers are operated in pulsed mode near room temperature. The company has designed, constructed, and demonstrated a multi-laser instrument that operates with these noncryogenic lasers and is capable of detecting various trace pollutants in vehicular exhaust, including NO, NH3, and N2O (which already have been demonstrated), as well as CO (which will be demonstrated when the laser is available). Aerodyne Research, Inc., also has forged a strong partnership with ESP, the industry leader in the automotive emissions testing market. Both parties are committed to the commercialization of this promising technology.


1. Fraser MP, Cass GC. Detection of excess ammonia emissions for in-use vehicles and the implications for fine particle control. Environmental Science and Technology 1998;32:1053-1057.

2. Baum MM, Kiyomiya ES, Kumar S, Lappas AM, Lord III HC. Multicomponent remote sensing of vehicle exhaust emissions by dispersive IR and UV spectroscopy. 10th CRC On-Road Vehicle Emissions Workshop, San Diego, CA, March 27-29, 2000.

3. Wilson RD, Durbin TD, Norbeck JM. Ammonia emissions from light duty vehicles. 10th CRC On-Road Vehicle Emissions Workshop, San Diego, CA, March 27-29, 2000.

4. Shores RC, Walker JT, Harris CB, McCulloch RB, Rodgers MO, Pearson JR. Measurement of ammonia emissions from EPA's instrumented vehicle. 10th CRC On-Road Vehicle Emissions Workshop, San Diego, CA, March 27-29, 2000.

5. Kean AJ, Harley RA, Sawyer RF, Littlejohn D, Zucker DJ, Kendall GR. On-road measurement of ammonia and other motor vehicle exhaust emissions. 10th CRC On-Road Vehicle Emissions Workshop, San Diego, CA, March 27-29, 2000.

6. Baum MM, Kiyomiya ES, Kumar S, Lappas AM, Kapinus VA, Lord HC. Multicomponent remote sensing of vehicle exhaust by dispersive absorption spectroscopy. 2. Direct on-road ammonia measurements. Environmental Science and Technology 2001;35:3735-3741.

7. Durbin TD, Wilson RD, Norbeck JM, Miller JW, Huai T, Rhee SH. Estimates of the emission rates of ammonia from light-duty vehicles using standard chassis dynamometer test cycles. Atmospheric Environment 2002;36:1475-1482.

8. Perrino C, Catrambone M, Bucchianico ADMD, Allegrini I. Gaseous ammonia in the urban area of Rome, Italy and its relationship with traffic emissions. Atmospheric Environment 2002;36:5385-5394.

9. Nelson Jr. DD, Zahniser MS, McManus JB, Kolb CE, Jimenez JL. A tunable diode laser system for the remote sensing of on-road vehicle emissions. Applied Physics B 1998;67:433-441.

10. Jimenez JL, Koplow MD, Nelson Jr. DD, Zahniser MS, Schmidt SE. Characterization of on-road vehicle NO emissions by a TILDAS remote sensor. Journal of the Air and Waste Management Association 1999;49:463-470.

11. Jimenez JL, McManus JB, Shorter JH, Nelson DD, Zahniser MS, Koplow M, McRae GJ, Kolb CE. Cross road and mobile tunable infrared laser measurements of nitrous oxide emissions from motor vehicles. Chemosphere: Global Change Science 2000;2:397-412.

Journal Articles on this Report : 1 Displayed | Download in RIS Format

Other project views: All 2 publications 1 publications in selected types All 1 journal articles
Type Citation Project Document Sources
Journal Article Nelson DD, Shorter JS, McManus JB, Zahniser MS. Sub-part-per-billion detection of nitric oxide in air using a thermoelectrically cooled mid-infrared quantum cascade laser spectrometer. Applied Physics B 2002;75(2-3):343-350. 68D00270 (Final)
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Supplemental Keywords:

noncryogenic tunable infrared laser monitor, on-road vehicle, emissions, ammonia, remote sensing, quantum cascade laser, automotive, diesel, CO, NO, hydrocarbons, carcinogens, cw lead salt diode laser, sensor, small business, SBIR., RFA, Scientific Discipline, Air, Ecosystem Protection/Environmental Exposure & Risk, Chemical Engineering, air toxics, Environmental Chemistry, Chemistry, Monitoring/Modeling, mobile sources, Environmental Monitoring, tropospheric ozone, Engineering, Engineering, Chemistry, & Physics, Environmental Engineering, remote sensing, noncryogenic laser, monitoring, vehicle emissions, hydrocarbon, stratospheric ozone, Ammonia, automotive emissions, spectroscopic studies, automotive, trucks, carbon dioxide, hydrocarbons, diode laser spectrometer

SBIR Phase I:

A Noncryogenic Tunable Diode Laser Monitor for On-Road Vehicle Emissions  | Final Report