ARB Research Seminar

This page updated June 19, 2013

Evaluation of Portable Emisions Measurement Systems (PEMS) for Inventory Purposes and the Not-To-Exceed Heavy-Duty Diesel Engine Regulation

Thomas D. Durbin, Ph.D., Kent Johnson, Ph.D. Candidate, J. Wayne Miller, Ph.D., and David R. Cocker III, Ph.D., Department of Chemical and Environmental Engineering, College of Engineering, and Center for Environmental Research and Technology (CE-CERT), University of California, Riverside

October 02, 2008
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA

Research Project


Over the past few years, the use of portable emissions measurement systems (PEMS) has expanded considerably for in-use measurements and in the development of regulations. In recent years, the U.S. Environmental Protection Agency (EPA) and the California Air Resources Board (CARB) have promulgated regulations that require in-use emissions measurements from heavy-duty diesel trucks in a defined portion of the engine map known as the Not-To-Exceed (NTE) zone. This new requirement to measure in-use emissions means that PEMS will be needed for regulatory compliance. PEMS are also important tools for the assessment of in-use emissions for emissions inventory purposes. Prior to this program, a limited number of studies had evaluated the performance of PEMS, but most of these studies were performed on early technology versions of PEMS or were performed by the instrument manufacturers themselves.

The goal of this program was to evaluate the performance of PEMS under a variety of in-use and other operating conditions. For this program, PEMS were evaluated against the University of California at Riverside's (UCR's) Mobile Emissions Laboratory (MEL), which complies with the Federal Reference Method requirements. The program was conducted in two phases. In the first phase, four commercial PEMS were compared with the MEL for measuring emissions from a back-up generator (BUG) over steady-state loads and a diesel truck on transient and steady-state chassis dynamometer tests. For the second phase of the program, the MEL was used to perform an on-road validation of PEMS for the Measurement Allowance program. Measurement allowances are needed to account for measurement error associated with PEMS use in the field, instead of testing the engine on a stationary dynamometer in an environmentally controlled laboratory. The over-the-road results were compared against the measurement allowances developed using the Monte Carlo model simulation. In conjunction with this program, a complete a cross-laboratory emissions correlation with the MEL was conducted with an engine dynamometer laboratory at the Southwest Research Institute (SwRI) in San Antonio, Texas, as well as a full 1065 audit of the MEL. The results of both phases of this project will be summarized and discussed in this presentation.

Speaker Biography

Thomas D. Durbin, Ph.D., is an associate research engineer in the emissions and fuels research group of CE-CERT (Center for Environmental Research and Technology), University of California, Riverside. Dr. Durbin conducts research in a broad range of topics related to vehicle emissions including particulate matter (PM) emissions, diesel, biodiesel, and gasoline fuels, portable emissions measurement systems (PEMS), and the unregulated species such as ammonia, N2O, and toxics. Dr Durbin conducts research in CE-CERT's state-of-of-the-art emissions test facilities including a heavy-duty mobile emissions laboratory, a heavy-duty engine dynamometer laboratory, and a light-duty chassis dynamometer laboratory. Dr. Durbin is also extensively involved with in-field measurements of emissions from passenger cars, heavy-duty trucks, and construction equipment. Prior to joining the emissions and fuel research group, Dr. Durbin was involved in several other areas of research at CE-CERT including renewable energy and fuel sources and advanced vehicle technologies. Dr. Durbin received his doctorate degree in Physics from the University of California, Riverside, in 1994 where the primary focus of his dissertation was the study of Si films and solid lubricants.

For a complete listing of the ARB Research Seminars and the related documentation
for the seminars please view the Main Seminars web page