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A portable emissions measurement system (PEMS) is a vehicle emissions testing device that is small and light enough to be carried inside or moved with a
motor vehicle A motor vehicle, also known as motorized vehicle or automotive vehicle, is a self-propelled land vehicle, commonly wheeled, that does not operate on Track (rail transport), rails (such as trains or trams) and is used for the transportation of pe ...
that is being driven during testing, rather than on the stationary rollers of a
dynamometer A dynamometer or "dyno" for short, is a device for simultaneously measuring the torque and rotational speed ( RPM) of an engine, motor or other rotating prime mover so that its instantaneous power may be calculated, and usually displayed by ...
that only simulates real-world driving. Early examples of mobile vehicle emissions equipment were developed and marketed in the early 1990s by
Warren Spring Laboratory Warren Spring Laboratory was a UK government environmental science research centre that operated in Stevenage, Hertfordshire from 1958 until its closure in 1994. Described by '' New Scientist'' as "Britain's leading laboratory for environmental ...
UK during the early 1990s, which was used to measure on-road emissions as part of the UK Environment Research Program. Governmental agencies like
United States Environmental Protection Agency The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it be ...
(USEPA) and various states and private entities have begun to use PEMS in order to reduce both the costs and time involved in making mobile emissions decisions. The
European Commission The European Commission (EC) is the executive of the European Union (EU). It operates as a cabinet government, with 27 members of the Commission (informally known as "Commissioners") headed by a President. It includes an administrative body o ...
introduced PEMS as a mandatory requirement for light-duty vehicle type approval in 2016 by ammending the regulation that was established in 2007.


Introduction of PEMS

Leo Breton of the US EPA invented the Real-time On-road Vehicle Emissions Reporter (ROVER) in 1995. The first commercially available device was invented by Michal Vojtisek-Lom, and developed by David Miller of Clean Air Technologies International (CATI) Inc. in Buffalo, New York in 1999. These early field devices used engine data from either an on-board diagnostics (OBD) port, or directly from an engine sensor array. The first unit was developed for, and sold to - Dr. H. Christopher Frey of North Carolina State University (NCSU) for the first on-road testing project, which was sponsored by the North Carolina Department of Transportation. David W. Miller, who co-founded CATI, first coined the phrase "Portable Emissions Measurement System" and "PEMS" when working on a 2000 New York City Metropolitan Transportation Agency bus project with Dr. Thomas Lanni of the New York State Department of Environmental Conservation, as a short-hand description of the new device. Other governmental groups and universities soon followed, and quickly began to use the equipment due to its balance of accuracy, low cost, light weight, and availability. From 1999 through 2004, research groups such as Virginia Tech, Penn State, and Texas A&M Transportation Institute, Texas Southern University and others began to use PEMS in border crossing projects, roadway evaluations, traffic control methods, before-and-after scenarios, and ferries, planes, and off-road vehicles, to explore what was possible outside of a lab environment. A project performed in April 2002 by the
California Air Resources Board The California Air Resources Board (CARB or ARB) is the "clean air agency" of the government of California. Established in 1967 when then-governor Ronald Reagan signed the Mulford-Carrell Act, combining the Bureau of Air Sanitation and the Moto ...
(CARB) - using non-1065 PEMS equipment, tested 40 trucks over a period of 2½ days; of which, 22 trucks were tested on road in Tulare, California. During this time, a high-profile project performed with early PEMS equipment was the World Trade Center (WTC) Ground Zero Project in lower Manhattan, testing concrete pumpers, bulldozers, graders, and later - diesel cranes on Building #7 - 40 stories high. Other early PEMS projects such as Dr. Chris Frey's field work was used by the USEPA in the development of the MOVES Model. However, users such as regulators and vehicle manufacturers had to wait for ROVER to be commercialized to conduct actual measurements of mass emissions rather than depend on estimates of mass emissions using data the OBD port, or a direct engine measurement, in order to have a more defensible data set. This push led to a new 2005 standard known as CFR 40 Part 1065. Many governmental entities (such as the USEPA and the
United Nations Framework Convention on Climate Change The United Nations Framework Convention on Climate Change (UNFCCC) established an international environmental treaty to combat "dangerous human interference with the climate system", in part by stabilizing greenhouse gas concentrations in th ...
or
UNFCCC The United Nations Framework Convention on Climate Change (UNFCCC) established an international environmental treaty to combat "dangerous human interference with the climate system", in part by stabilizing greenhouse gas concentrations in th ...
) have identified target mobile-source pollutants in various mobile standards as
CO2 Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
,
NOx In atmospheric chemistry, is shorthand for nitric oxide () and nitrogen dioxide (), the nitrogen oxides that are most relevant for air pollution. These gases contribute to the formation of smog and acid rain, as well as affecting tropo ...
, Particulate Matter (PM),
Carbon Monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
(CO),
Hydrocarbons In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ex ...
(HC), to ensure that emissions standards are being met. Further, these governing bodies have begun adopting in-use testing program for non-road diesel engines, as well as other types of internal combustion engines, and are requiring the use of PEMS testing. It is important to delineate the various classifications of the latest 'transferable' emissions testing equipment from-time PEMS equipment, in order to best understand the desire of portability in field-testing of emissions.


Economic advantage of PEMS equipment

Because a PEMS unit is able to be carried easily by one person from jobsite to jobsite, and can be used without the requirement of 'team lifting', the required emissions testing projects are economically viable. Simply put, more testing can be done more quickly, by less workers, dramatically increasing the amount of testing done in a certain time period. This in turn, significantly reduces the 'cost per test', yet at the same time increases the overall accuracy required in a 'real-world' environment. Because the law of large numbers will create a convergence of results, it means that repeatability, predictability, and accuracy are enhanced, while simultaneously reducing the overall cost of the testing.


On-road emissions patterns identified by PEMS

Nearly all modern engines, when tested new and according to the accepted testing protocols in a laboratory, produce relatively low emissions well within the set standards. As all individual engines of the same series are supposed to be identical, only one or several engines of each series get tested. The tests have shown that: # The bulk of the total emissions can come from relatively short high-emissions episodes # Emissions characteristics can be different even among otherwise identical engines # Emissions outside of the bounds of the laboratory test procedures are often higher than under the operating and ambient conditions comparable to those during laboratory testing #Emissions deteriorate significantly over the useful life of the vehicles #There are large variances among the deterioration rates, with the high emissions rates often attributable to various mechanical malfunctions These findings are consistent with published literature, and with the data from a myriad of subsequent studies. They are more applicable to spark-ignition engines and considerably less to diesels, but with the regulation-driven advances in diesel engine technology (comparable to the advances in
spark-ignition A spark-ignition engine (SI engine) is an internal combustion engine, generally a petrol engine, where the combustion process of the air-fuel mixture is ignited by a spark from a spark plug. This is in contrast to compression-ignition engines, t ...
engines since the 1970s) it can be expected that these findings are likely to be applicable to the new generation diesel engines. Since 2000, multiple entities have used PEMS data to measured in-use, on-road emissions on hundreds of diesel engines installed in school buses, transit buses, delivery trucks, plow trucks, over-the-road trucks, pickups, vans, forklifts, excavators, generators, loaders, compressors, locomotives, passenger ferries, and other on-road, off-road and non-road applications. All the previously listed findings were demonstrated; in addition, it was noticed that extended idling of engines can have a significant impact on the emissions during subsequent operation. Also, PEMS testing identified several engine "anomalies" where fuel-specific NOx emissions were two to three times higher than expected during some modes of operation, suggesting deliberate alterations of the engine control unit (ECU) settings. Such data set can be readily used for developing emissions inventories, as well as to evaluate various improvements in engines, fuels, exhaust after-treatment and other areas. (Data collected on "conventional" fleets then serves as "baseline" data to which various improvements are compared.) This data set can also be examined for compliance with not-to-exceed (NTE) and in-use
emissions standards Emission standards are the legal requirements governing air pollutants released into the atmosphere. Emission standards set quantitative limits on the permissible amount of specific air pollutants that may be released from specific sources o ...
, which are 'US-based' emission standards that require on-road testing.


Accuracy of PEMS

It is often difficult for PEMS to offer the same accuracy and variety of species measured as is possible with top-of-the-line laboratory instrumentation because PEMS are typically limited in size, weight and power consumption. For this reason, objections were raised against using PEMS for compliance verification. But there is also the potential for inaccuracy in fleet emissions deduced from laboratory measurements. For this reason, European WLTP results from PEMS will be weighted with a conformity factor of 2.1 (1.5 after 2019), i.e. the emissions measured by the PEMS are allowed to be a factor 2.1 higher than the limit. It is expected that a variety of on-board systems will be designed, ranging from bread-box sized PEMS to instrumented trailers towed behind the tested truck. The benefits of each approach need to be considered in light of other sources of errors associated with emissions monitoring, notably vehicle-to-vehicle differences, and the emissions variability within the vehicle itself.


Additional PEMS criteria

PEMS need to be safe enough to use on public roads. During testing, portable emissions systems could attach extensions of the tailpipe, add lines and cables outside the vehicle, carry lead-acid batteries in the passenger compartment, have hot components accessible to bystanders, block emergency exits, interfere with the driver, or have loose components that could be caught in moving parts. Modifications to or disassembly of the tested vehicle such as drilling into the exhaust or removing intake air system need to be examined for their acceptance by both fleet managers and drivers, especially on passenger-carrying vehicles. The test equipment can not draw excessive electrical load from the test vehicle. Instead, sealed lead-acid batteries, fuel cells and generators have been used as external power sources, though they may add other hazards during driving. The more time and expertise installation of the equipment requires, the greater the cost of testing, limiting the number of vehicles that can be tested. More testing is also possible with equipment that is versatile enough to be used on more than one type of vehicle. The weight and size of the equipment and consumables like calibration gases might limit moving to a sufficient number locations. Any restrictions on transport of hazardous materials (i.e.
Flame ionization detector A flame ionization detector (FID) is a scientific instrument that measures analytes in a gas stream. It is frequently used as a detector in gas chromatography. The measurement of ion per unit time make this a mass sensitive instrument. Standalo ...
(FID) fuel or calibration gases) need to be taken into the account. The ability of the test crew to repair PEMS in the field using locally available resources can also be essential.


PEMS suitability to application

Ultimately, it should be demonstrated to show that a PEMS is suitable to the desired application. If the ultimate goal is to verify the compliance with in-use emissions requirements, a fleet of vehicles with known characteristics – including engines with dual-mapping and otherwise non-compliant engines – should be made available for testing. It should be then up to the PEMS manufacturers to practically demonstrate how these non-compliant vehicles can be identified using their system.


Testing volume and safe repeatability

In order to achieve the required amount of 'testing volume' needed to validate real-world testing, three points must be considered: #System accuracy #Federal and/or state health and safety guidelines and/or standards #Economic viability based on the first two points. Once a particular portable emissions system has been identified and pronounced as accurate, the next step is to ensure that the worker(s) are properly protected from work hazards associated with the task(s) being performed in the use of the testing equipment. For example, typical functions for a worker may be to transport the equipment to the jobsite (i.e. car, truck, train, or plane), carry the equipment to the jobsite, and lift the equipment into position.


Advantages of PEMS

On-road vehicle emissions testing is very different from the laboratory testing, bringing both considerable benefits and challenges: As the testing can take place during the regular operation of the tested vehicles, a large number of vehicles can be tested within a relatively short period of time and at relatively low cost. Engines than cannot be easily tested otherwise (i.e.,
ferry boat A ferry is a ship, watercraft or amphibious vehicle used to carry passengers, and sometimes vehicles and cargo, across a body of water. A passenger ferry with many stops, such as in Venice, Italy, is sometimes called a water bus or water tax ...
propulsion engines) can be tested. True real-world emissions data can be obtained. The instruments have to be small, lightweight, withstand difficult environment, and must not pose a safety hazard. Emissions data is subject to considerable variances, as real-world conditions are often neither well defined nor repeatable, and significant variances in emissions can exist even among otherwise identical engines. On-road emissions testing therefore requires a different mindset than the traditional approach of testing in the laboratory and using models to predict real-world performance. In the absence of established methods, use of PEMS requires careful, thoughtful, broad approach. This should be considered when designing, evaluating and selecting PEMS for the desired application. A recent example of PEMS advantages over laboratory testing is the Volkswagen (VW) Scandal of 2015. Under a small grant from the
International Council on Clean Transportation The International Council on Clean Transportation (ICCT) is an independent nonprofit organization incorporated under Section 501(c)(3) of the US tax code. It provides technical and scientific analysis to environmental regulators. It is funded by ...
(icct), Daniel K Carder of
West Virginia University West Virginia University (WVU) is a public land-grant research university with its main campus in Morgantown, West Virginia. Its other campuses are those of the West Virginia University Institute of Technology in Beckley, Potomac State College ...
(WVU) uncovered on-board software "cheats" that VW had installed on some diesel passenger vehicles (
Dieselgate The Volkswagen emissions scandal, sometimes known as Dieselgate or Emissionsgate, began in September 2015, when the United States Environmental Protection Agency (EPA) issued a notice of violation of the Clean Air Act to German automaker Vol ...
scandal). The only way the discovery could have been made was by a non-programmed, random, on-road evaluation - utilizing a PEMS device. VW is now liable for over US$14 billion in fines. In 2016, these latest developments led to a global resurgence of interest in smaller, lighter, integrated and cost-effective "non-1065" PEMS, similar to the demonstration on ''MythBusters'' 2011 Episode 171 of "Bikes and Bazookas", in which a non-1065 PEMS was used to establish the difference between car and motorcycle pollution.


Subcategory: integrated PEMS (iPEMS)

Overview of integrated PEMS (iPEMS) development In response to
Dieselgate The Volkswagen emissions scandal, sometimes known as Dieselgate or Emissionsgate, began in September 2015, when the United States Environmental Protection Agency (EPA) issued a notice of violation of the Clean Air Act to German automaker Vol ...
, the " Real Driving Emissions" (RDE) standard has been developed in the European Union (EU) which has, in turn, increased the demand for smaller, lighter, more portable, less expensive and integrated PEMS equipment kits. iPEMS equipment is not presently able to be used as a "certification" device in the U.S. Definition of iPEMS The following features are common to the smaller and lighter class of iPEMS equipment: # A complete, self-contained, and internally modular Portable Emissions Measurement System (PEMS) kit # including a built-in, on-board power source, # no more than 7 kg in total weight (including carrying case, exhaust connectors, and any additional equipment required for use), # able to be carried by one person, # which can be transported through an airport terminal and stored in the overhead bin of an airplane; # once deployed at a field site, the iPEMS has the ability to be testing vehicles within 30 minutes (assuming that the required onboard power pack has been charged); # the length of testing time capability from the integrated power pack is a minimum of two hours; # minimum pollutant testing capabilities must include: Nitrogen Oxides (NOx), Carbon Dioxide (CO2), and either Particulate Matter (PM) or Particulate Number (PN); # testing accuracy must be within 10% (or better) of a 1065 PEMS. Advantages of iPEMS over 1065 PEMS equipment The advantage of iPEMS equipment is that they are designed to both complement 1065 PEMS in addition to providing expanded capabilities, which are being driven by the requirements for quicker decision-making compounded by the 2015 Volkswagen scandal. These devices are presently being pursued by both the European Union (EU) and China for their RDE Programs.


See also

* National Ambient Air Quality Standards (US) *
Volkswagen emissions scandal The Volkswagen emissions scandal, sometimes known as Dieselgate or Emissionsgate, began in September 2015, when the United States Environmental Protection Agency (EPA) issued a notice of violation of the Clean Air Act to German automaker Vol ...


References


External links


Request for grant application by Texas Commission on Environmental Quality for a project that required the use of a PEMS
*Study of snowmobile emissions by
University of Denver The University of Denver (DU) is a private university, private research university in Denver, Colorado. Founded in 1864, it is the oldest independent private university in the Mountain States, Rocky Mountain Region of the United States. It is ...
uses PEMS to detect emission
Winter Motor-Vehicle Emissions in Yellowstone National Park
*M. J. Bradley & Associates, Inc. monitored emissions from off-road vehicles at the World Trade center reconstruction sit
Investigation of Diesel Emission Control Technologies on Off-Road Construction Equipment at the World Trade Center and PATH Re-Development Site
*Report by
North Carolina State University North Carolina State University (NC State) is a public land-grant research university in Raleigh, North Carolina. Founded in 1887 and part of the University of North Carolina system, it is the largest university in the Carolinas. The universit ...
for the USEPA with recommendations for the next generation of PEMS devices to be develope
Recommended Strategy For On-Board Emission Data Analysis and Collection For the New Generation Model
*Biodiesel study for the North Carolina Department of Transportation performed by North Carolina State University uses a PEMS device to gather emissions comparison dat
Operational Evaluation of Emissions and Fuel Use of B20 Versus Diesel Fueled Dump Trucks
*
Environmental Protection Agency A biophysical environment is a biotic and abiotic surrounding of an organism or population, and consequently includes the factors that have an influence in their survival, development, and evolution. A biophysical environment can vary in scale f ...
information page on PEM
Science for the 21st Century
*The
Imperial College London Imperial College London (legally Imperial College of Science, Technology and Medicine) is a public research university in London, United Kingdom. Its history began with Prince Albert, consort of Queen Victoria, who developed his vision for a cu ...
(UK) Centre for Transport Studies conducted a vehicle performance study and gathered emissions data along the M42 Motorway using a PEMS devic
Instantaneous Vehicle Emission Monitoring
*Recent uses and presentations of PEMS
University of California (UCR) College of Engineering - Center for Environmental Research and Technology (CE-CERT)
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