TM

Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

RI 9667

REPORT OF INVESTIGATIONS/2006

Effectiveness of Selected

Diesel Particulate Matter Control

Technologies for Underground Mining

Applications: Isolated Zone Study, 2003
Report of Investigations 9667 

Effectiveness of Selected Diesel Particulate Matter Control 

Technologies for Underground Mining Applications: 

Isolated Zone Study, 2003

By Aleksandar D. Bugarski, Ph.D., George H. Schnakenberg, Jr., Ph.D., James D. Noll, Ph.D., 

 Steven E. Mischler, Larry D. Patts, Jon A. Hummer, and Shawn E. Vanderslice 

DEPARTMENT OF HEALTH AND HUMAN SERVICES 

Centers for Disease Control and Prevention 

National Institute for Occupational Safety and Health 

Pittsburgh Research Laboratory 

Pittsburgh, PA 

May 2006
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 FAX: 513–533–8573 

 Telephone: 1–800–35–NIOSH 

 (1–800–356–4674) 

 e-mail: pubstaft@cdc.gov 

 Website: www.cdc.gov/niosh 

This document is in the public domain and may be freely copied or reprinted. 

————————————————————— 

Disclaimer: Mention of any company or product does not constitute endorsement by the National 

Institute for Occupational Safety and Health (NIOSH). In addition, citations to Web sites external 

to NIOSH do not constitute NIOSH endorsement of the sponsoring organizations or their programs 

or products. Furthermore, NIOSH is not responsible for the content of these Web sites. 

DHHS (NIOSH) Publication No. 2006–126
CONTENTS 

 Page 

Abstract............................................................................................................................... 1 

Introduction......................................................................................................................... 2 

Objectives ........................................................................................................................... 3 

Methodology....................................................................................................................... 3 

Tested vehicles and emissions control technologies....................................................... 4 

Vehicles and engines................................................................................................... 4 

Preparation of vehicles for the study..........................................................4 

Control technologies ................................................................................................... 5 

Fuel formulations...................................................................................................... 14 

Isolated zone testing...................................................................................................... 18 

The test site ............................................................................................................... 19 

Duty cycles................................................................................................................ 23 

Ventilation................................................................................................................. 24 

Equipment, instrumentation, and methods for ambient sampling, measurements, 

 and analysis................................................................................................................. 25 

Standard sampling method for elemental carbon (EC)............................................. 25 

High-volume sampling for EC.................................................................................. 25 

DPM concentration measurements with a TEOM series 1400a ambient 

 particulate monitor................................................................................................. 27 

Measurement of size distribution and particle number concentrations using a 

 scanning mobility particle sizer ............................................................................. 27 

Concentration of CO, NO and NO2 measured by an Industrial Scientific iTX 

 multigas monitor .................................................................................................... 28 

Downstream concentrations of CO and CO2 measured by an Innova 1312 

 photoacoustic multigas monitor............................................................................. 29 

Measurements of exhaust temperature and engine back pressure ............................ 29 

Measurement of ambient temperature and barometric pressure............................... 29 

Measurements of ventilation rates ............................................................................ 30 

Analysis of samples collected using standard and high-volume methods................ 31 

Sampling and measurement methodology................................................................ 32 

Sampling strategy...................................................................................................... 34 

Calculation of the effects of control technologies .................................................... 35 

Exhaust emission testing............................................................................................... 37 

Engine operating conditions ..................................................................................... 37 

Equipment, instrumentation, and methods for measurement of exhaust pipe 

 emissions.....................................................................................38 

Results and discussion ...................................................................................................... 40 

Results of isolated zone tests ........................................................................................ 40 

Ventilation rates........................................................................................................ 40 

Effects of control technologies on EC concentrations.............................................. 45 

Effects of control technologies on TPM ................................................................... 47 

Effects of control technologies on particle size distribution and number 

 concentration.......................................................................................................... 48 
ii

Effects of control technologies on ambient concentrations of CO, CO2, NO, 

 and NO2.................................................................................................................. 55 

Effects of filtration systems on exhaust temperature and engine back pressure....... 63 

Results of tailpipe emissions measurements................................................................. 66 

Particulate matter emissions: EC .............................................................................. 66 

Particulate matter emissions: Bacharach smoke number.......................................... 68 

Emissions of CO, CO2, NO, and NO2....................................................................... 69 

Summary........................................................................................................................... 74 

References......................................................................................................................... 77 

ILLUSTRATIONS 

 1. Engelhard DPX DPF system on truck #92128 ............................................................ 9 

 2. CleanAIR Systems DPF system on truck #92133 ..................................................... 10 

 3. DCL BlueSky DPF system on LHD #92506 ............................................................. 11 

 4. Mac’s Mining Repair filtration system on LHD #92506 used for testing 

 Donaldson P604516 and Filter Services DFEs....................................................... 12 

 5. ECS Cattrap DPF system on LHD #92526................................................................ 13 

 6. DCL MINE–X Sootfilter DPF system on haul truck #99942.................................... 14 

 7. Mixing and storage vessels for B20 and B50 biodiesel #2 diesel fuel blends........... 15 

 8. Fueling station in isolated zone.................................................................................. 17 

 9. Isolated zone at the SMC Nye Mine.......................................................................... 20 

10. The isolated zone and duty cycles for trucks #92128 and #92133 ............................ 21 

11. The isolated zone and duty cycles for LHDs #92506, #92526, and #99942 ............. 22 

12. The high-volume DPM sampling train ...................................................................... 26 

13. Downstream sampling station showing instrumentation and grid supporting 

 DPM samplers, anemometer, and iTX gas monitor................................................ 31 

14. Distribution of samplers across sampling station showing the locations of the 

 high-volume sampling heads and three standard samplers..................................... 33 

15. Ventilation rates for the tests involving #92128........................................................ 40 

16. Ventilation rates for the tests involving #92133........................................................ 41 

17. Ventilation rates for the tests involving #92506........................................................ 41 

18. Ventilation rates for the tests involving #92526........................................................ 42 

19. Ventilation rates for the tests involving #99942........................................................ 42 

20. TPM concentrations at the downstream sampling station for the baseline test on 

 LHD #99942 ........................................................................................................... 48 

21. Size distribution of aerosols in mine air for truck #92128: the baseline case and 

 and Engelhard DPX DPF case (three measurements for each test).......................... 51 

22. Size distribution of aerosols in mine air for LHD #99942: the baseline case 

 DCL MINE–X DPF case (three measurements for each)....................................... 51 

23. Size distribution of aerosols in mine air for truck #92506: the baseline 1 case 

 (two measurements) and baseline 2 case (three measurements)............................. 52 

24. Size distribution of aerosols in mine air for LHD #92526: the baseline case and 

 Engelhard PTX DOC + muffler case (two measurements each) ............................ 53 
iii

25. Size distribution of aerosols in mine air for LHD #92526 equipped with Engelhard 

 PTX DOC and muffler: #2 diesel, biodiesel B20, and biodiesel B50 (two 

 measurements each)................................................................................................ 54 

26. Size distribution of aerosols in mine air for LHD #99942 equipped with muffler: 

 #1 diesel and #2 diesel (three measurements each) ................................................ 55 

27. Normalized CO2 concentrations for the tests with LHD #92506 .............................. 57 

28. Normalized CO2 concentrations for the tests with LHD #92526 .............................. 58 

29. Normalized CO2 concentrations for the tests with LHD #99942 .............................. 58 

30. Normalized NO concentrations for the tests with LHD #92526................................ 59 

31. Normalized NO concentrations for the tests with LHD #99942................................ 60 

32. Normalized NO2 concentrations at the downstream sampling station for the tests 

 with haul truck #92128 ........................................................................................... 61 

33. Normalized NO2 concentrations at the downstream sampling station for the tests 

 with LHD #99942 ................................................................................................... 61 

34. Normalized NO2 concentrations at the downstream and vehicle sampling stations 

 for the baseline (#1 diesel) and DCL MINE–X DPF system tests with LHD 

 #99942.........................................................................................62 

35. Temperature frequency distribution and cumulative frequency distribution used to 

 determine T30 for haul truck #92133 during CleanAIR DPF system test............... 63 

36. Exhaust temperature and engine back pressure trace recorded during the isolated 

 zone test of the CleanAIR DPF system................................................................... 65 

37. Reduction of EC emissions at TCS............................................................................ 68 

TABLES 

 1. Vehicles from the SMC Nye Mine inventory equipped with DPF systems prior to 

 the study.................................................................................................................... 6 

 2. Vehicles from the SMC Nye Mine inventory that were retrofitted with DPF 

 systems as part of the study ...................................................................................... 7 

 3. Results of fuel analysis .............................................................................................. 16 

 4. Fuel used in this study................................................................................................ 18

 5. Tests performed in the isolated zone ......................................................................... 19 

 6. Ventilation rate coefficients and normalized contributions of the test vehicles/ 

 configurations to CO2 concentrations ..................................................................... 43 

 7. Effects of control technologies on VR-normalized net EC concentrations ............... 45 

 8. Effects of control technologies on CO2-normalized net EC concentrations.............. 46 

 9. Concentrations of TPM under 0.8 μm at the downstream sampling station.............. 47 

10. Effects of control technologies on concentration of aerosols in mine air.................. 50 

11. Concentrations of CO, CO2, NO, and NO2 at the downstream sampling station 

 normalized to the MSHA ventilation rate for the test engine used......................... 56 

12. Results of analysis of exhaust temperatures and engine back pressures ................... 64 

13. Effects of control technologies on elemental carbon emissions ................................ 67 

14. Effects of control technologies on DPM emissions: Bacharach smoke number ....... 69 

15. CO tailpipe emissions ................................................................................................ 70 

16. CO2 tailpipe emissions............................................................................................... 71 

17. NO tailpipe emissions................................................................................................ 72 

18. NO2 tailpipe emissions............................................................................................... 73 
iv

ACRONYMS AND ABBREVIATIONS USED IN THIS REPORT 

ACGIH American Conference of Governmental Industrial Hygienists 

ASTM American Society for Testing and Materials 

B20 biodiesel blend, 20% biodiesel and 80% #2 diesel 

B50 biodiesel blend, 50% biodiesel and 50% #2 diesel 

BL baseline 

CAT Caterpillar, Inc. 

CDT Clean Diesel Technologies, Inc. (Stamford, CT) 

Ce-Pt cerium-platinum 

CFR Code of Federal Regulations 

CH4 methane 

CCO2 net contribution of the tested vehicle to air concentrations of 

 carbon monoxide 

CECCO2 net contribution of the tested vehicle to air concentrations of 

 elemental carbon per carbon monoxide concentrations 

C[ECCO2]CT net CO2-normalized concentrations of elemental carbon for control 

 technology (CT) case 

C[ECCO2]BL net CO2-normalized concentrations of elemental carbon for 

 baseline (BL) case 

Ci net contribution of the tested vehicle to air concentrations of 

 pollutant for control technology case 

Ci BL net contribution of the tested vehicle to air concentrations of 

 pollutant for baseline case 

ci measured concentration 

ci,VR ventilation-adjusted concentrations 

ci VR,DOWN ventilation-adjusted concentrations at the downstream sampling 

 station 

ci,UP measured concentration at the upstream sampling station 

CO carbon monoxide 

CO2 carbon dioxide 

CPC condensation particle counter 

CT control technology 

CV coefficient of variation 

D_p particle diameter 

DFE disposable filter element 

dN/(d log D_p) normalized particle number concentration 

DOC diesel oxidation catalyst 

DPF diesel particulate filter 

DPM diesel particulate matter 

EC elemental carbon 

GMD geometric mean diameter 

GSD geometric standard deviation 

HC hydrocarbon 

He helium 
v

HEPA high-efficiency particulate air (filter) 

hh:mm:ss hours : minutes : seconds (absolute time) 

HI high idle 

HV high-volume 

IMA–NA Industrial Minerals Association–North America 

ISO International Organization for Standardization 

LHD load-haul-dump 

LI low idle 

LOQ limit of quantification 

MARG Methane Advisory Research Group 

MSHA Mine Safety and Health Administration 

MTI Mining Technologies International (Sudbury, Ontario, Canada) 

N/A not available 

NIOSH National Institute for Occupational Safety and Health 

NMA National Mining Association 

NO nitric oxide 

NO2 nitrogen dioxide 

NPT national pipe thread 

NSSGA National Stone, Sand and Gravel Association 

O2 oxygen 

OC organic carbon 

PC personal computer 

PRL Pittsburgh Research Laboratory (NIOSH) 

Pt platinum 

SMC Stillwater Mining Co. 

SMPS scanning mobility particle sizer 

SS stainless steel 

STEL short-term exposure limit (ACGIH) 

SwRI Southwest Research Institute (San Antonio, TX) 

T30 exhaust temperature exceeded 30% of the time 

TCS torque converter stall 

TEOM tapered-element oscillating microbalance 

TLV threshold limit value (ACGIH) 

TPM total particulate matter 

TWA time-weighted average (ACGIH) 

USBM U.S. Bureau of Mines 

USWA United Steelworkers of America 

VR ventilation rate 

VRj, MSHA MSHA-prescribed ventilation rate 

VRC ventilation rate coefficient 
vi

UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT 

cm centimeter 

cm

2

 square centimeter 

ft foot 

ft3

/min cubic foot per minute 

g/m3 gram per cubic meter 

g/mL gram per milliliter 

gal gallon 

hp horsepower 

hr hour 

in inch 

in H2O inches of water 

kg kilogram 

kJ/kg kilojoule per kilogram 

kPa kilopascal 

kW kilowatt 

L liter 

L/min liter per minute 

lb pound 

m meter 

m3

 cubic meter 

m3/min cubic meter per minute 

m3/s cubic meter per second 

min minute 

mm millimeter 

mm

2

/s square millimeter per second 

nm nanometer 

oz ounce 

ppm part per million 

s second 

V ac volt, alternating current 

yd3

 cubic yard 

μg/m3 microgram per cubic meter 

μg/m3/ppm microgram per cubic meter per parts per million 

μm micrometer 

% vol percent by volume 

% wt percent by weight 

#/cm3 particle number per cubic centimeter 

°C degree Celsius 

°F degree Fahrenheit 
EFFECTIVENESS OF SELECTED 

DIESEL PARTICULATE MATTER CONTROL TECHNOLOGIES 

FOR UNDERGROUND MINING APPLICATIONS: 

ISOLATED ZONE STUDY, 2003 

By Aleksandar D. Bugarski, Ph.D.,1 George H. Schnakenberg, Jr., Ph.D.,2 James D. Noll, Ph.D.,3

Steven E. Mischler,4

 Larry D. Patts,4 Jon A. Hummer,5 and Shawn E. Vanderslice5

ABSTRACT 

The National Institute for Occupational Safety and Health designed and conducted a 

study in an underground metal mine to assess the effects of selected diesel emissions 

control technologies on the concentrations of diesel particulate matter and gases in 

underground mine air. The control technologies studied included diesel particulate filter 

(DPF) systems, filtration system with disposable filter elements, diesel oxidation catalytic 

converter, and biodiesel blends. Each technology was tested on a mining vehicle 

operated in an isolated area of an underground mine supplied with fresh air. These 

isolated zone tests allowed for the operation of vehicles under conditions and over 

duty cycles that closely mimic actual duty cycles of production equipment. The DPF 

systems reduced the elemental carbon (EC) concentrations in mine air between 88% and 

99%. The same systems reduced total particulate matter (TPM) concentrations in mine 

air by approximately 75%. The biodiesel blends B20 and B50 caused a reduction in the 

EC concentrations of 26% and 48%, respectively. Those blends also reduced TPM 

concentrations by 9% and 24%, respectively. The use of #1 diesel fuel reduced EC 

concentration by 13% compared to #2 diesel fuel. An increase in nitrogen dioxide 

concentration of up to two times was seen when platinum-catalyzed DPF systems 

were tested. 

 

1

Mechanical engineer. 

2

Research physicist. 

3

Research chemist. 

4

Physical scientist. 

5

Engineering technician. 

Pittsburgh Research Laboratory, National Institute for Occupational Safety and Health, Pittsburgh, PA. 
2

INTRODUCTION 

The National Institute for Occupational Safety and Health (NIOSH) designed and 

conducted a study in an isolated area of an underground metal mine to assess the effects 

of selected diesel emissions control technologies on the concentrations of diesel 

particulate matter (DPM) and gases in underground mine air. The study was organized 

under the auspices of the Metal/Nonmetal Diesel Partnership formed by NIOSH, the 

National Mining Association (NMA), the National Stone, Sand and Gravel Association 

(NSSGA), the United Steelworkers of America (USWA), the MARG Diesel Coalition, 

and the Industrial Minerals Association–North America (IMA–NA). The objective of the 

study was to provide real-world information on the performance of selected control 

technologies. This information is critical to making an informed selection of technically 

and economically feasible controls to curtail particulate matter emissions from existing 

and new diesel-powered vehicles in underground metal and nonmetal mines. This study 

is one facet toward the ultimate goal of reducing the exposures of underground mine 

workers to DPM and other diesel emissions, which have been recognized as an 

occupational health concern. 

This study was needed because most of the current knowledge on the performance of 

diesel particulate filter (DPF) systems and other diesel emissions control technologies 

was obtained through laboratory and in-use evaluations of technologies designed 

primarily for on-highway applications. According to our best knowledge, only two 

comprehensive studies have offered insight into the problems associated with the use of 

modern DPF systems on underground mining vehicles. One study was conducted at 

Noranda, Inc.’s Brunswick Mining and Smelting Mine near Bathurst, New Brunswick, 

Canada, the other at Inco, Ltd.’s Stobie Mine in Sudbury, Ontario, Canada [McGinn 

2001; Bugarski and Schnakenberg 2001, 2002]. Both studies were conducted under the 

sponsorship of the Diesel Emissions Evaluation Program.6 The U.S. mining industry 

expressed concern that this rather limited knowledge is not sufficient to help select, with 

confidence, the appropriate emissions control technology needed to comply with the rule 

limiting exposure of underground metal and nonmetal miners to DPM (30 CFR7

 57.5060). 

The partnership agreed that a series of comprehensive field evaluations of DPFs in 

several underground mines was needed to establish confidence in the performance of 

DPF systems and other DPM-reducing controls and to determine their viability. 

NIOSH and Stillwater Mining Co. (SMC) personnel developed a test protocol and 

selected the control technologies for the isolated zone study. The series of tests 

comprising the study was conducted at the SMC Nye Mine in southern Montana from 

May 19, 2003, to May 30, 2003. The 2-week study was conducted by a team consisting 

of NIOSH researchers and SMC personnel from the industrial hygiene, maintenance, and 

operations departments. Representatives of the partnership and the Mine Safety and 

Health Administration (MSHA) were present during some portions of the effort. This 

document is a comprehensive report of this study. 

 

6

The Diesel Emissions Evaluation Program (DEEP) is a research consortium aimed at reducing exposure to 

diesel exhaust in underground mining (www.deep.org). 7

Code of Federal Regulations. See CFR in references. 
3

OBJECTIVES 

The objective of this study was to determine the in situ effectiveness of the selected 

technologies available to the underground mining industry for reducing particulate matter 

and gaseous emissions from diesel-powered equipment. Each technology was tested on a 

mining vehicle, operated under conditions that closely resembled actual production 

scenarios, in an isolated area of an underground mine supplied with fresh air (isolated 

zone). 

The study was designed to provide SMC and the general mining community with better 

insights into the performance of control technologies and enable them to identify the 

appropriate technology for reducing emissions from diesel-powered equipment. The 

focus of this study was on technologies that offer solutions for reducing DPM emissions. 

The following control technologies were studied: DPFs, disposable DPM filters, diesel 

oxidation catalytic converter, and reformulated fuels. 

This short-term study addressed some issues related to the selection and installation of 

filtration systems, but was not able to address the other important issues related to the 

implementation and operation of DPFs, namely, equipment-specific installation 

problems, regeneration of DPF systems during the production cycle, maintenance, 

reliability, and durability. Addressing these issues will require more comprehensive and 

complex long-term studies that address the multiplicity of issues concerning 

implementation. 

The primary technical objective of this study was to assess the effects of selected control 

technologies on concentrations of DPM and gases in the mine air. Most of this effort was 

dedicated to evaluating the performance of selected state-of-the-art DPF systems that 

were designed and supplied by several major manufacturers. Additional efforts were 

made to assess the effect of two different biodiesel blends (B20 and B50), #1 and #2 

diesel, and selected diesel oxidation catalyst (DOC) on air quality and emissions. 

METHODOLOGY 

A limited set of vehicles representative of those from the Nye Mine production fleet 

were selected to test selected control technologies. With the assistance of the vehicle 

operators, the study team developed a typical duty cycle for each of the two types of 

production vehicles selected. Each test consisted of operating the test vehicle in the 

isolated zone repeatedly over the appropriate duty cycle while a set of measurements of 

DPM and gases was conducted upwind, downwind, and on the vehicle. The ventilation 

air quantity was measured and controlled for each test. 

The isolated zone measurements were complemented with measurements of DPM and 

gas concentrations in the exhaust system of the tested vehicles obtained while the 

vehicles were parked in the Nye Mine surface shop and their engines operated at three 

steady-state conditions. 
4

TESTED VEHICLES AND EMISSIONS CONTROL TECHNOLOGIES 

Vehicles and Engines 

SMC selected the diesel equipment to represent typical vehicles and power packages 

from the SMC Nye Mine production fleet. The selected vehicles—two trucks and three 

load-haul-dump (LHD) vehicles—are classified as heavy-duty production machines. 

These vehicles were representative of (1) the mine fleet, (2) the duty cycle for that type of 

vehicle, and (3) their effect on mine air quality. The engines powering these vehicles are 

also representative of the fleet. Some of the selected vehicles represent those of the fleet 

that routinely heavily load their engines, while others are assumed to represent those that 

perform tasks that produce less of a load on the engines. A short description of the 

vehicles used in this study follows. 

MTI DT–1604 Trucks #92128 and #92133 

MTI DT–1604 (Mining Technologies International, Sudbury, Ontario, Canada) is a truck 

with rated load of 14,545 kg (32,000 lb) and box capacity of 8.2 m3

 (10.8 yd3). Truck 

#92128 is powered by a Deutz BF6M 1013FC, and truck #92133 is powered by a BF6M 

1013ECP. 

MTI LT–350 LHD #92506 

MTI LT–350 LHD has a rated load of 3,409 kg (7,500 lb) and bucket capacity of 1.9 m3

(2.5 yd3). This model is powered by a Deutz BF4M 1013C. 

Caterpillar Elphinstone R1300 LHD #92526 

Caterpillar Elphinstone R1300 (Caterpillar Elphinstone Pty. Ltd., Burnie, Tasmania, 

Australia) LHD has a rated load of 6,500 kg (14,333 lb) and bucket capacity of 2.8 m3

(3.7 yd3

). This particular vehicle is powered by a Caterpillar CAT 3306 DITA engine 

rated at 123 kW (165 hp). At the SMC Nye Mine, the #92526 and similar vehicles are 

typically used at a draw point for loading MTI DT 1604 trucks. 

Caterpillar Elphinstone R1500 LHD #99942 

Caterpillar Elphinstone R1500 LHD has a rated load of 10,200 kg (22,491 lb) and bucket 

capacity of 4.8 m3

 (6.3 yd3). This unit is powered by a Caterpillar CAT 3306 DITA 

engine rated at 164 kW (220 hp). At the SMC Nye Mine, the #99942 and similar 

vehicles are typically used at a draw point for loading MTI DT 1604 trucks. 

Preparation of Vehicles for the Study 

The major modifications to the vehicles/engines were those related to the temporary 

installation of various exhaust system configurations. The DPF systems on vehicles 

#92128 and #99942 were permanently installed on those vehicles as replacements to the 
5

original oxidation catalytic converter and muffler configurations. The other evaluated 

systems were installed on the vehicles as temporary replacements of the existing exhaust 

systems specifically for the tests. For the purpose of assessing the effects of the bare 

engines on the concentration of DPM and gases and establishing baselines for the control 

technology comparisons, any existing oxidation catalytic converter and muffler 

combinations or DPFs were temporarily removed from the vehicles and replaced with an 

adequate muffler. 

The Caterpillar 3306 DITA engines are designed to release unfiltered crankcase 

emissions (primarily oil mist and exhaust blowby) to the atmosphere. A closed-loop 

filtered crankcase breather system was installed on both of the Caterpillar engines used in 

the tests in order to capture crankcase breather effluent and eliminate its contribution to 

DPM and hydrocarbons to the mine air. The Deutz BF4M1013 and BF6M1013 engines, 

which powered three of the test vehicles (#92128, #92133, and #92506), are designed 

with a closed-loop crankcase breather system. 

Prior to the study, all vehicles and engines had been serviced by the mine personnel using 

an emissions-assisted maintenance program. The necessary preparations for the tests, 

including changes on exhaust systems, were usually made in the surface shop on the day 

before the vehicle was to be used in a test. 

Control Technologies 

The primary objective of this study was to evaluate the effectiveness of six DPF systems 

in reducing the concentration of DPM in the underground mine environment. 

Additionally, the effects of replacing the currently used #1 diesel with the blends of 

“yellow grease” biodiesel and with #2 diesel (B20 and B50) were investigated. The 

effects of a diesel oxidation catalytic converter on diesel emissions were also examined.

Diesel Particulate Filter Systems 

Several commercially available DPF systems were examined during this study. An 

Engelhard DPX installed on truck #92128 and a DCL MINE–X installed on LHD #99942 

were selected from a list of DPF systems that were installed on the production vehicles 

prior to this study (Table 1). In addition, the other four filtration systems—a CleanAIR 

Systems DPF, a DCL BlueSky DPF, an ECS Cattrap DPF, and a Mac’s Mining Repair 

filtration system with a Donaldson high-temperature disposable filter element (DFE)—

were selected and temporarily fitted to a selected vehicle (Table 2). 
6

Table 1.—Vehicles from the SMC Nye Mine inventory equipped with DPF systems prior to the study 

Vehicle 

# 

Vehicle 

Type 

Engine 

Manufacturer 

Engine 

Model 

Vent. 

Rate, m3

/s 

(ft3/min) 

DPF 

Manufacturer 

DPF 

Model 

DPF 

Brand 

Name 

DPF 

Media 

Type 

DPF 

Media 

Size, 

cm × cm 

(in × in) 

DPF 

Regeneration 

91580 Locomotive Deutz BF6M 

1013FC 

5.66 

(12,000) Engelhard 9308 DPX Cordierite 

26.7× 

30.5 

(10.5× 

12.0) 

platinum 

washcoat 

91582 Locomotive Deutz BF6M 

1013ECP 

5.66 

(12,000) Engelhard 9308 DPX Cordierite 

26.7× 

30.5 

(10.5× 

12.0) 

platinum 

washcoat 

92054 

Wagner 

ST–2D 

LHD 

Deutz BF4M 

1013FC 

3.77 

(8,000) DCL 5C57 

11 

MINE–

X Cordierite 

22.9× 

30.5 

(9.0× 

12.0) 

platinum 

washcoat 

92122 

MTI DT–

1604 

haul truck 

Deutz BF4M 

1013FC N/A Engelhard 9308 DPX Cordierite 

26.7× 

30.5 

(10.5× 

12.0) 

platinum 

washcoat 

92128 

MTI DT–

1604 

haul truck 

Deutz BF6M 

1013FC 

5.66 

(12,000) Engelhard 9308 DPX Cordierite 

26.7× 

30.5 

(10.5× 

12.0) 

platinum 

washcoat 

92130 

MTI DT–

1604 

haul truck 

Deutz BF6M 

1013ECP 

5.66 

(12,000) Engelhard 9308 DPX Cordierite 

26.7× 

30.5 

(10.5× 

12.0) 

platinum 

washcoat 

92131 

MTI DT–

1604 

haul truck 

Deutz BF6M 

1013ECP 

5.66 

(12,000) Engelhard 9308 DPX Cordierite 

26.7× 

30.5 

(10.5× 

12.0) 

platinum 

washcoat 

92135 

MTI DT–

1604 

haul truck 

Deutz BF6M 

1013ECP 

5.66 

(12,000) Engelhard 9308 DPX Cordierite 

26.7× 

30.5 

(10.5× 

12.0) 

platinum 

washcoat 

92140 EJC 515 

haul truck Deutz BF6M 

1013ECP 

5.66 

(12,000) Engelhard 9308 DPX Cordierite 

26.7× 

30.5 

(10.5× 

12.0) 

platinum 

washcoat 

92535 

Elphinstone 

 R–1300 

LHD 

CAT 3306 

DITA 

4.72 

(10,000) DCL 5C57 

11 

MINE–

X Cordierite 

22.9× 

30.5 

(9.0× 

12.0) 

platinum 

washcoat 

92608 MTI LT–

270 LHD Deutz BF4M 

1012C 

3.07 

(6,500) DCL 5C57 

11 

MINE–

X Cordierite 

22.9× 

30.5 

(9.0× 

12.0) 

platinum 

washcoat 
7

Table 2.—Vehicles from the SMC Nye Mine inventory that were retrofitted with DPF systems 

as part of the study 

Vehicle 

# Vehicle Type 

Engine 

Manufacturer 

Engine 

Model 

Vent. 

Rate, m3

/s, 

(ft3

/min) 

Filter 

Manufacturer 

Filter 

Model 

Filter 

Type 

Filter 

Media 

Filter 

Media 

Size, 

cm × cm 

(in × in) 

Filter 

Regeneration 

Concept 

92128 

MTI DT–

1604 

haul truck 

Deutz BF6M 

1013FC 

5.66 

(12,000) Engelhard DPX Cordierite 

26.7 × 

25.4 

(10.5 × 

10.0) 

platinum 

washcoat 

92133 

MTI DT–

1604 

haul truck 

Deutz BF6M 

1013ECP 

5.66 

(12,000) 

CleanAIR 

Systems 

FPA 

158W — Cordierite 

28.7 × 

35.6 

(11.3 × 

14.0) 

platinum 

washcoat 

+ Ce-Pt 

fuel-borne 

catalyst 

92506 MTI LT–350 

LHD Deutz BF4M 1013C 

5.43 

(11,500) DCL 

3211-

SA6CG1-

21 

BlueSky Silicon 

carbide 

26.7 × 

25.4 

(10.5 × 

10.0) 

catalyzed 

+ onboard 

electrical 

regeneration 

92506 MTI LT–350 

LHD Deutz BF4M 1013C 

5.43 

(11,500) Donaldson P604516 — 

Hightemp. 

disposable 

32.4 × 

66.0 

(12.7 × 

26.0) 

disposable 

92526 

Elphinstone 

R–1300 

LHD 

CAT 

3306 

DITA 

(165 hp) 

4.72 

(10,000) ECS CT28 Cattrap Cordierite 

30.8 × 

38.1 

(12.0 × 

15.0) 

base metal 

washcoat 

+ offboard 

electrical 

regeneration, DOC 

on outlet 

side 

99942 

Elphinstone 

R–1500 

LHD 

CAT 

3306 

DITA 

(220 hp) 

7.08 

(15,000) DCL 5C57 

11 

MINE–

X Cordierite 

22.9 × 

27.9 

(9.0 × 

11.0) 

platinum 

washcoat 

The DPF systems were selected to allow for evaluation of in-use performance of 

representative systems that are using two most popular ceramic monolith media: 

(1) a cordierite wall-flow monolith from Corning represented in DPF systems from 

Engelhard, CleanAIR Systems, ECS, and DCL (MINE–X), and (2) and a silicon carbide 

wall-flow monolith from Ibiden used in the DCL (BlueSky) DPF system. The detailed 

description of the cordierite and silicon carbide monolith media is available elsewhere 

[Schnakenberg and Bugarski 2002]. In addition, the study was used to assess in-use 

performance of a high-temperature DFE from Donaldson. 

The other dimension of this study was to test DPF systems that use both passive 

and active regeneration schemes. The Engelhard DPX, CleanAIR Systems, and DCL 

MINE–X DPF systems are passive systems. The mine has been successfully operating 

passive DPF systems on heavy-duty trucks that were generally operating at high engine 

loads. The mine’s experience with medium- and light-duty vehicles has not been as 

positive because passive DPF systems installed on such vehicles have failed to regenerate 

reliably. The DCL BlueSky system is an active system that requires the off-shift 

placement of the vehicle at a regeneration station. The ECS Cattrap can generally be 
8

classified as an active/passive system because it is primarily regenerated passively, and 

although it requires periodic active cleaning and regeneration, the period between those 

corresponds to regular engine maintenance and thus poses little operational burden. The 

Donaldson filter element is disposable, and it is designed to be replaced with a fresh one 

each time engine back pressure caused by the DPM loaded element exceeds that specified 

by engine manufacturers for each individual engine model. 

The newly introduced DPF systems were installed on the vehicles and used in production 

for at least 2 days prior to testing in the isolated zone. This time was used to (1) verify 

the performance of the system with respect to DPF regeneration, (2) examine various 

operational issues, and (3) condition the DPF medium. The Donaldson filters were new 

and had virtually no running time on them prior to testing. 

A detailed description of the tested filtration systems follows. 

Engelhard DPX DPF System 

The Engelhard DPX DPF (Engelhard Corp., Iselin, NJ) (Figure 1) uses a Corning 

cordierite wall-flow monolith filter element that has been “washcoated” with a 

proprietary platinum-based catalyst. Theoretically, the DPF should passively 

(spontaneously during the course of vehicle operation) regenerate (burn off the 

accumulated DPM) during an engine’s duty cycle if the exhaust temperature exceeds 

350 °C for an extended period (at least 30% of the engine’s operating time). Although 

the system is designed primarily for control of DPM emissions, significant reductions in 

emissions of carbon monoxide (CO) and unburned hydrocarbons are expected owing to 

the platinum-based catalyst. Recent studies [Schnakenberg and Bugarski 2001] showed 

that some platinum washcoated filters promoted the oxidation of nitric oxide (NO) to 

nitrogen dioxide (NO2). Although several similar systems were used on production 

vehicles at the Nye Mine for extended periods of time, NO2 emissions were not 

quantified by mine personnel. This DPF had accumulated approximately 4,600 hr in 

production before being tested in this study. 
9

Figure 1.—Engelhard DPX DPF system on truck #92128. 

CleanAIR Systems DPF System 

The CleanAIR Systems DPF system (CleanAIR Systems, Inc., Santa Fe, NM) (Figure 2) 

uses a Corning cordierite wall-flow monolith filter element washcoated with a proprietary 

platinum-based catalyst. The system is used in conjunction with a fuel additive from 

Clean Diesel Technologies, Inc., Stamford, CT, called Platinum Plus. This bimetallic 

catalyst that contains both platinum and cerium can be used effectively at a dosage level 

substantially lower than other fuel-borne catalysts. Theoretically, the DPF system, with 

this fuel-borne catalyst, should passively regenerate during the duty cycle, which results 

in exhaust temperatures over 330 °C for extended periods (at least 30% of the operating 

time) of the cycle. According to the manufacturer, this system does not promote 

conversion of NO to NO2. The system is perceived as a viable alternative to platinumcatalyzed DPF systems such as Engelhard DPX and DCL MINE–X that are known for 

their tendency to increase secondary emissions of NO2. 

The fuel additive was mixed into the fuel tank of the test vehicle during fueling. The 

recommended dosage of 30 oz for 125 gal of fuel was used. 

The system was delivered several weeks before the study, installed on truck #92133, and 

had accumulated approximate 200 hr of run time prior to testing. 
10

Figure 2.—CleanAIR Systems DPF system on truck #92133. 

DCL BlueSky DPF System 

The DCL BlueSky (DCL International, Inc., Concord, Ontario, Canada) system 

(Figure 3) is designed as an active system that partially regenerates during the regular 

duty cycle and requires periodic regeneration using heat supplied by an onboard electrical 

heater. The heating coils are placed at the inlet end of the filter element. During the 

regeneration, the vehicle needs to be parked next to the offboard regeneration station that 

provides the power and combustion air needed for the electrical regeneration process. 

The system uses a silicon carbide wall-flow monolith filter element with thermal 

properties that allow regeneration in less than 2 hr. The frequency and duration of 

regeneration sessions are primarily affected by engine DPM emissions and therefore by 

engine design, mechanical condition, and nature of the duty cycle. 

This particular system was made available for the study by the SMC East Boulder Mine. 

The system was decommissioned from the original application prior to this study because 

the heating element had failed and the vehicle operators were not able to regenerate the 

DPF. SMC personnel had replaced the heating element, and the system was installed on 

LHD #92506 (see Figure 3). Owing to the limited space available on the vehicle, the 

system was installed as a temporary arrangement and was used only in this study. The 

system was removed following the tests and not placed into production because, in part, 

the mine was unable to provide the necessary infrastructure in production zones to 

support an onboard electrically regenerated system. 
11

Figure 3.—DCL BlueSky DPF system on LHD #92506. 

Donaldson P604516 DFE in Mac’s Mining Repair Filtration System 

At the time of study, the Donaldson P604516 high-temperature DFE from Donaldson 

Co., Inc., Minneapolis, MN, was in the developmental stage. Since this DFE was 

designed to handle between 8.5 and 11.3 m3

/min (300 and 400 ft3/min) of exhaust, two 

DFEs in parallel were needed to handle the exhaust flow rate of the Deutz BF4L1013C 

engine (Figure 4). DFEs were used as part of a filtration system that was designed and 

built by Mac’s Mining Repair, Huntington, UT. Owing to the limited space available on 

the vehicle, the system was temporarily installed on LHD #92506. 

This DFE uses a deep-bed filter that collects particulate matter throughout its depth 

and generates relatively low exhaust back pressure when new. The filter medium is 

resistant to water and/or other combustion byproducts. It has been designed for exhaust 

temperatures up to 343 °C (650 °F). The filtration system was removed from the test 

vehicle shortly after the trial. The filter was run for approximately 2 hr prior to the 

test. The filtration efficiency of such a DFE can be expected to increase during the first 

several hours of operation. Shortly after the study, this high-temperature DFE 

became commercially available and listed on the MSHA DPM control technology table 

[MSHA 2005]. 
12

 

 Figure 4.—Mac’s Mining Repair filtration system on LHD #92506 used for testing 

Donaldson P604516 and Filter Services DFEs. 

ECS Cattrap DPF System 

Engine Control Systems Ltd. (ECS), Newmarket, Ontario, Canada, supplied the Cattrap 

DPF system (Figure 5) as a retrofit to LHD #92526. It is a passive system that uses a 

cordierite wall-flow monolith coated with a base-metal catalyst. Theoretically, the 

system should passively regenerate during vehicle operation if the exhaust temperature is 

over 390° C for a significant portion (at least 30%) of the time. The system also requires 

periodic removal from the vehicle for cleaning and regeneration using the ECS 

CombiClean station. The frequency of the periodic cleaning and regeneration is 

dependent on the degree to which the system regenerates during equipment operation. 

The exhaust temperature traces obtained for LHD #92526 during the preselection period 

indicated that available exhaust heat is theoretically sufficient to support almost complete 

regeneration of the DPF. The manufacturer predicted that cleaning would be needed 

approximately every 250 hr, the same period as scheduled preventive maintenance 

sessions. However, the actual frequency of the regeneration sessions was supposed to be 

established empirically after the filter was installed and the vehicle was operated over an 

extended period of time. 

The ECS DPF system included a DOC mounted downstream of the DPF. The DOC is 

designed to reduce emissions of CO and unburned hydrocarbons. 

The ECS CombiClean cleaning station consists of a vacuum cleaner with HEPA filter, 

electrical heater, and compressed air supply. The DPF is removed from the vehicle and 

placed on the station for cleaning and complete regeneration. The three-step process 
13

starts with removal of loose soot and ash from the filter using reverse flow of air provided 

by the vacuum cleaner attached to the inlet end of the filter. The vacuuming is followed 

by a controlled thermal regeneration. The heat for thermal regeneration is provided by 

electric heaters, while the combustion air is provided by a compressor. The thermal 

regeneration process is designed to be relatively slow in order to minimize the thermal 

stress on the cordierite DPF element. At the last stage of the process, the vacuum is used 

to remove remaining ash from the filter. The complete cleaning process takes 

approximately 8 hr. The system was delivered and installed during the first week of 

testing. Therefore, the system was in service for only about 2 days prior to testing. The 

system was decommissioned shortly after the trial. 

Figure 5.—ECS Cattrap DPF system on LHD #92526. 

DCL MINE–X Sootfilter DPF System 

The DCL MINE–X Sootfilter DPF system (DCL International, Concord, Ontario, 

Canada) (Figure 6), tested on LHD #99942, uses a platinum-catalyzed cordierite filter 

element. This system is conceptually very similar to the Engelhard DPX DPF described 

earlier. 
14

Figure 6.—DCL MINE–X Sootfilter DPF system on haul truck #99942. 

The DCL DPF system was initially installed on LHD #92535. After the system failed to 

passively regenerate on that vehicle, it was cleaned and reinstalled on LHD #99942. 

Prior to the study, the system had accumulated approximately 800 hr in production. 

Engelhard PTX DOC 

The Engelhard PTX DOC (Engelhard Corp., Iselin, NJ) uses ceramic honeycomb 

substrate that is washcoated with proprietary catalyst formulation. This DOC is designed 

to control emissions of CO, hydrocarbons (HCs), and soluble organics emitted by diesel 

engines. The DOC used in this study was made available by the SMC Nye Mine. The 

DOC was installed on LHD #92526 and degreened for approximately 2 hr before the 

first test. 

Fuel Formulations 

All diesel-powered vehicles used in underground operations at the SMC Nye Mine are 

fueled with #1 diesel supplied by a local refinery (Cenex, Columbus, MT). This 

particular fuel exceeds MSHA requirements (30 CFR 57.5065) for diesel fuels used in 

underground mines. Using higher-quality and more expensive #1 diesel instead of 

#2 diesel was part of the mine’s strategy to reduce the exposure of underground miners to 

diesel emissions. At the mine’s request, NIOSH included a test of #2 diesel fuel. 

The neat biodiesel for this study was supplied by Griffin Industries, Inc., Cold Spring, 

KY (Biodiesel G–3000). The B20 (20% neat biodiesel G–3000 with the balance #2 

diesel) and B50 (50% neat biodiesel with the balance #2 diesel) blends were made at the 
15

surface shop at Nye Mine (Figure 7). The quantities of #2 diesel and neat biodiesel in the 

blends were determined volumetrically. 

The #2 diesel that is used by diesel-powered vehicles for surface operations at the SMC 

Nye Mine was supplied from the same refinery as the #1 diesel. 

The samples of #2 diesel, B20, and B50 were sent for detailed analysis to Southwest 

Research Institute (SwRI), San Antonio, TX. The selected properties of the fuels are 

summarized in columns 4–6 in Table 3. The Cenex refinery provided some limited data 

on the properties of the fuels supplied to the Nye Mine (see Table 3, columns 7–8). 

Griffin Industries also provided a certificate of the analysis for the biodiesel G–3000. 

Some of the information from the certificate is included in Table 3 (see column 9). 

 Figure 7.—Mixing and storage vessels for B20 and B50 

biodiesel #2 diesel fuel blends. 
16

Table 3.—Results of fuel analysis 

SwRI Cenex Griffin 

Type of analysis Method 

Unit 

of 

measure 

#2 

diesel B20 B50 #1 diesel 

#2 

diesel B100 

1 2 3 4 5 6 7 8 9 

Cetane Number ASTM 

D613 N/A 43.2 47.6 51.5 42.8 43.2 53.5 

Aromatics ASTM 

D1319 % vol 30.9 N/A N/A N/A N/A N/A 

Olefins — % vol 2.1 N/A N/A N/A N/A N/A HC Type 

Saturates — % vol 67.0 N/A N/A N/A N/A N/A 

Density ASTM 

D4052 g/mL 0.85 N/A N/A 0.82 0.85 N/A 

Sulfur Content ASTM 

D5453 ppm 299 238 159 125 366 25 

Nitrogen Content ASTM 

D4629 ppm 28.0 36.3 43.4 N/A N/A N/A 

Oxygen By 

differ. % wt N/A 2.49 5.56 N/A N/A N/A 

Heat of Combustion ASTM 

D240 kJ/kg 42,647 41,526 39,923 N/A N/A N/A 

Flash Point ASTM 

D93 °C 71.1 73.3 78.9 57.2 66.1 >120 

Viscosity, 40 oC ASTM 

D445 mm2

/s N/A 2.61 3.25 N/A N/A 4.65 

A 500-gal tank (Figure 8) with the fuel for use in this study was temporarily located in 

the isolated zone in a sealed-off crosscut about halfway along the test course section of 

52E drift. A hand pump was used to transfer fuel to the fuel tanks of the test vehicles. 

The volume of the transferred fuel was measured using an electronic fuel meter (Great 

Plains Industries, Inc., Wichita, KS). The fuel tank of the test vehicle was filled to the 

same level before and after each test. The measured fuel volumes were used to estimate 

fuel consumed during the test. 

The fuel consumption of the engine powering LHD #92526 was measured using a 

portable fuel metering system (Max Machinery, Inc., Series 710, Model 213). The 

capacity of the fuel metering system was not sufficient to measure the fuel consumption 

of Deutz engines powering #92128, #92133, and #92506 because the Deutz fuel system 

also supplies a high volume of fuel for engine cooling. The electrical components of the 

fuel metering system failed during the test on #99442 with #2 diesel fuel. The fuel 

consumption data are not included in this report. 
17

Figure 8.—Fueling station in isolated zone. 

The initial plan was to fill the 500-gal tank in the isolated zone with #1 diesel and use it 

as the baseline fuel for this study. Unfortunately, the tank was filled with #2 diesel from 

the large surface reservoir designated for use by surface vehicles. The percentages of 

#1 and #2 diesel fuel in the fuel used in each test were estimated from the fuel sulfur 

analysis and are shown in Table 4. The fuel tanks of the vehicles used for tests with 

biodiesel blends and #2 diesel were drained prior to the tests and fueled from the verified 

sources. The fuel comparison tests involving LHD #99942 were run after the mistake 

with filling the supply tank with #2 diesel was discovered. The proper fuels were 

dispensed to the fuel tank of LHD #99942. For the tests intended to show the difference 

between #1 and #2 diesel fuels with LHD #92506, the fuel actually differed very little 

(89.6% vs. 100% #2 diesel); these tests can serve to demonstrate the repeatability of the 

isolated zone test method. 
18

Table 4.—Fuel used in this study

Vehicle Test Exhaust System 

Configuration Date Fuel 

#92128 Baseline Muffler 05/26/03 #1 (27.5%) / #2 (72.5%) diesel 

DPF Engelhard DPX 05/26/03 #1 (47.3%) / #2 (52.7%) diesel 

#92133 Baseline Muffler 05/22/03 #1 (19.1%) / #2 (80.9%) diesel 

DPF CleanAIR Systems 05/22/03 #1 (31.4%) / #2 (68.6%) diesel 

Baseline #1 

diesel 

Muffler 05/23/03 #1 (10.4%) / #2 (89.6%) diesel 

Baseline #2 

diesel 

Muffler 05/23/03 #2 (100%) diesel 

DPF DCL BlueSky 05/21/03 #1 (75.0%) / #2 (25.0%) diesel 

#92506 

DFE Donaldson P604516 05/23/03 #1 (14.7%) / #2 (85.3%) diesel 

Baseline #1 

diesel 

Muffler 05/27/03 #1 (74.1%) / #2 (25.9%) diesel 

Baseline + 

DOC 

Engelhard PTX and 

muffler 

05/27/03 #1 (52.2%) / #2 (47.8%) diesel 

DPF ECS Cattrap 05/24/03 #1 (94.8%) / #2 (5.2%) diesel 

Biodiesel B20 Engelhard PTX and 

muffler 

05/28/03 #2 (80.0%) / bio (20%) diesel 

#92526 

Biodiesel B50 Engelhard PTX and 

muffler 

05/28/03 #2 (50%) / bio (50%) diesel 

Baseline #1 

diesel 

Muffler 05/29/03 #1 (100%) diesel 

Baseline #2 

diesel 

Muffler 05/30/03 #2 (100%) diesel 

#99942 

DPF DCL MINE–X 05/29/03 #1 (100%) diesel 

ISOLATED ZONE TESTING 

The major part of this study was dedicated to establishing performance of the selected 

control technologies using isolated zone testing. These tests were designed to be a 

compromise between the genuineness of in situ measurements of workplace contaminant 

concentrations and personal exposures, and the repeatability and accuracy of the 

emissions measurements conducted under research laboratory conditions. The isolated 

zone tests allowed the operation of vehicles under conditions and over duty cycles that 

closely mimic actual production duty cycles of the respective equipment used. In 

addition, these tests were not compromised by artifacts usually generated under 

laboratory conditions while attempting to simulate real-life conditions and processes. 

Conversely, laboratory accuracy and repeatability cannot be matched in isolated zone 

testing primarily because engines are loaded by vehicles and controlled by humans rather 

than by a tightly controlled engine dynamometer. 

The effects of each of the selected control technologies on DPM and gas concentrations 

in the mine air were estimated from the measurements taken while each test vehicle was 

operated within the zone with and without control technologies. Corrections for the 
19

background concentrations of the pollutants were made by subtracting the results of 

measurements performed at the upstream end of the zone from the corresponding results 

obtained at the downstream end of the isolated zone. The efficiency of each 

aftertreatment system was determined by comparing the pollutant concentrations 

obtained with the system installed to those concentrations resulting from operating the 

same vehicle over the same duty cycle with only a muffler. In the tests designed for the 

assessment of the effects of fuel formulations, the emissions from the vehicles fueled 

with alternative fuels were compared to those from the same vehicle when fueled with 

baseline diesel fuel. All tests performed in the isolated zone over this 10-day study are 

listed in Table 5. 

Table 5.—Tests performed in the isolated zone 

Vehicle Test Type Exhaust System 

Configuration Date Operator 

#92128 Baseline for DPF Muffler 05/26/03 Jim 

DPF Engelhard DPX 05/26/03 Jim 

#92133 Baseline Muffler 05/22/03 Ed 

DPF CleanAIR Systems 05/22/03 Ed 

Baseline for DPFs with 

fuel 1 

Muffler 05/23/03 Chad 

Baseline for DPFs with 

fuel 2 

Muffler 05/23/03 Chad 

DPF DCL BlueSky 05/21/03 Charlie 

#92506 

Disposable DPF Donaldson P604516 05/23/03 Chad 

Baseline for DPF and 

DOC 

Muffler 05/27/03 Chad 

Baseline for biodiesel/ 

DOC 

Engelhard PTX and 

muffler 

05/27/03 Chad 

DPF ECS Cattrap 05/24/03 Chad 

Biodiesel B20 Engelhard PTX and 

muffler 

05/28/03 Chad 

#92526 

Biodiesel B50 Engelhard PTX and 

muffler 

05/28/03 Chad 

Baseline for DPF / 

#1 diesel 

Muffler 05/29/03 John 

Baseline for DPF / 

#2 diesel 

Muffler 05/30/03 John 

#99942 

DPF DCL MINE–X 05/29/03 John 

The Test Site 

The 530-m (1,739-ft) long isolated zone was located in 52E ramp in the east section of 

the SMC Nye Mine. The upstream end of the zone was situated approximately 150 m 

(492 ft) from the portal. The elevation of the portal is approximately 1,525 m (5,003 ft) 

above sea level. The location of the isolated zone relative to the portal is shown in 

Figure 9. The average cross-sectional dimensions of the isolated zone opening were 

approximately 2.75 by 3.5 m (9 by 11.5 ft). The ramp has a 9% rise toward the 

downstream end. 
20

Figure 9.—Isolated zone at the SMC Nye Mine. 

The site selected for the isolated zone met the following requirements: 

1. It was isolated from the other parts of the mine where diesel-powered equipment 

is used. 

2. It was ventilated with fresh air directly from the mine portal. 

3. The quality and quantity of the air were not compromised by portal traffic. 

4. The zone was sufficiently long and its cross-section was relatively small to ensure 

thorough mixing of the vehicle exhaust with the mine air at the planned 

ventilation rates and to ensure uniform contaminant distribution across the drift at 

the downstream sampling station. 

5. The ventilation controls allowed relatively uniform air quantity adjustment and 

control during the tests. 

6. Power to operate 110 V ac instruments was available at the downstream and 

upstream sampling stations. 

The schematic of the isolated zone is shown in Figures 10–11. For each test, the test 

vehicle was operated over the simulated duty cycle at and between the upstream and 

downstream load/dump points, which were approximately 300 m (984 ft) apart. The 

upstream sampling station was located approximately 90 m (295 ft) upstream of the 

upstream load/dump point. The downstream sampling station was located approximately 

140 m (459 ft) downstream of the downstream load/dump point. A third sampling point 

was located on the vehicle. The ventilation control doors were located approximately 60 

m (197 ft) downstream of the downstream sampling station. 

The stopes at the upstream and downstream load/dump points were approximately 8 m 

(26.2 ft) deep. Significant quantities of waste rock, sufficient to support the duty cycle 

for LHD vehicles, were available at upstream and downstream load/dump points. The 

refueling station was located in one of the sealed stopes about halfway between the 

upstream and downstream load/dump points. 
21

Figure 10.—The isolated zone and duty cycles for trucks #92128 and #92133 (not to scale). 
22

Figure 11.—The isolated zone and duty cycles for LHDs #92506, #92526, and #99942 (not to scale). 
23

Duty Cycles 

NIOSH and SMC Nye Mine personnel, including experienced vehicle operators, 

developed two well-defined, conservative, simple, and repeatable duty cycles, one for the 

haul trucks and one for the LHDs. Both test cycles simulated a typical production cycle 

for the respective equipment. 

The Duty Cycle for Trucks 

The duty cycle for trucks #92128 and #92133 is shown in Figure 10. It consisted of two 

major tasks simulating loading, one at the loading point and one at the dumping point, 

and two tramming tasks occurring between those points. The trucks were operated with 

their box loaded with ore for the entire cycle to keep the cycle simple and reduce 

variability. For safety reasons, the cycle was designed to keep the operator facing the 

direction of travel when the trucks were tramming up or down the ramp. The trucks 

started the cycle at the upstream dumping point by hauling a full box of ore up the ramp 

to the loading point. At the loading point, the operators simulated a loading cycle by 

repositioning the trucks for loading by an imaginary LHD. It was assumed that three 

buckets were required to load each of the trucks. Tramming down the ramp toward the 

dumping point followed the loading cycle. At the dumping point, the operator simulated 

unloading the box by engaging the hydraulics and loading the engine. After completion 

of this last task, a new cycle would start. 

Two full cycles, designated as warmup cycles, were executed during each test prior to the 

start of sampling at each of the three stations. The warmup cycles allowed the driver to 

become familiar with the cycle and to allow an initial buildup of exhaust contaminants 

prior to initiation of sampling. The tests were usually terminated after completing a 

number of full cycles. The average duration of a complete duty cycle for trucks was 

about 8 min. The duration of each test was dictated by the time required to acquire an 

adequate DPM sample for EC analysis and depended on the DPM reduction efficiency of 

the control technology being tested. 

Both the operator and test vehicle were kept the same for each pair of efficiency 

comparison tests (see Table 5). This practice reduced potential error created by different 

driving habits and other human factors. 

The Duty Cycle for LHDs 

The duty cycle for LHDs #92506, #92526, and #99942 is shown in Figure 11. It 

consisted of two very similar major load/dump tasks, one occurring at each of the 

load/dump points and two tramming tasks occurring between those points. The LHDs 

started their cycles at the upstream load/dump point with the bucket loaded with ore. The 

operator would first take the vehicle into the upstream stope and unload the bucket, 

retreat for the length of the vehicle, then advance forward and load the bucket again. The 

next step was to back the vehicle out of the stope and advance for two vehicle lengths 

up the ramp. At that location, the operator would engage the hydraulics to simulate 
24

loading of an imaginary truck and then back the vehicle to the starting point. This 

loading operation would be repeated three times. After the third execution, the loaded 

LHD vehicle would tram up the ramp to the downstream load/dump point. The LHD 

would execute three load/dump tasks similar to those performed at the upstream location. 

At the end of the load/dump session at the downstream point, the vehicle would tram 

loaded down the ramp to the upstream starting point to complete the cycle. It would then 

initiate a new cycle. 

At the start of each test, two full warmup cycles were executed prior to the start of 

sampling. The tests were usually terminated after completing a number of full cycles. 

The average duration of the duty cycle for LHDs was about 13 min. The duration of a 

test was dictated by the time required for collecting a sufficient DPM sample. 

LHDs #92526 and #99942 were operated by the same operator throughout all tests 

involving those vehicles (see Table 5). LHD #92506 was operated by the same operator 

for three out of four tests. A different miner operated the vehicle during the test with the 

DCL BlueSky DPF system. 

Ventilation 

The isolated zone was ventilated with fresh air from the portal (see Figure 9). Since no 

diesel-powered activity occurred upstream of the test zone just prior to or during a test, 

the level of diesel contamination in the ventilation air entering the test zone was very low. 

The initial intent was to maintain the ventilation rate (VR) in the main drift during each 

of the tests close to the VR determined by MSHA for the specific engine used in the test 

vehicle (see Table 2). That amount of air was assumed to provide enough protection to 

the operator and researchers, yet allow collecting adequate particulate samples in a 

reasonably short test period. In order to compensate for a potential increase in NO2

emissions, the VR was set to substantially exceed the MSHA VR during the tests 

involving the platinum-catalyzed DPF systems. The intent was to run tests involving the 

exhaust filters for a much longer period than for baseline or fuel tests to ensure the 

collection of sufficient sample material for the analysis. 

The analysis of the ventilation data collected during the tests conducted during the first 

week of the study showed an unacceptable variability for those tests when the VR was set 

close to the MSHA VR. Therefore, for the remainder of the tests, the VR was maintained 

at much higher levels, which were more easily controlled. 

Auxiliary ventilation was not supplied to the stopes at the upstream and downstream 

load/dump points. 
25

EQUIPMENT, INSTRUMENTATION, AND METHODS FOR 

AMBIENT SAMPLING, MEASUREMENTS, AND ANALYSIS 

This section describes the various equipment, instrumentation, and methods used in this 

study to collect particulate matter samples or directly measure concentrations of 

particulate matter and selected gases. 

Standard Sampling Method for Elemental Carbon (EC) 

The sampling train used for DPM sampling was identical to that used by MSHA for DPM 

compliance monitoring (30 CFR 57.5061). It consisted of a flow-controlled MSA Escort 

ELF Sampling Pump from Mine Safety Appliances Co., Pittsburgh, PA; and a 10-mm 

Dorr-Oliver Cyclone and SKC DPM Cassette, both from SKC, Inc., Eighty Four, PA. 

The SKC DPM Cassette contains a single-stage impactor with a nominal cut point of 

0.8 μm [Olson 2001], followed by two stacked 37-mm tissue quartz-fiber filters. The 

pumps were operated at 1.7 L/min. The pumps were calibrated at the mine at the 

beginning of the study. The flow rate for each of the sampling pumps was measured and 

recorded daily using a Gilibrator–2 bubble flow meter from Sensidyne, Clearwater, FL. 

If a measured flow rate deviated by more than 5%, the pump was recalibrated. 

The exposed SKC DPM Cassettes were shipped to the NIOSH Pittsburgh Research 

Laboratory (PRL) and analyzed by the PRL analytical laboratory for EC content using 

NIOSH Analytical Method 5040. 

High-volume Sampling for EC 

The preliminary estimates of the DPM concentrations for several control devices based 

upon laboratory data indicated that the standard sampling procedure would require 

extremely long sampling times to collect sufficient material to obtain accurate carbon 

analysis using NIOSH Analytical Method 5040. Therefore, NIOSH designed a highvolume (HV) sampling train (Figure 12) to accelerate the collection of adequate sample 

mass while maintaining the 0.8-μm cut point to separate diesel aerosol from the larger 

mine dust aerosols. This sample concentration objective was accomplished by increasing 

the sampling flow rate and decreasing the area of the collection filter. The sampling flow 

rate was increased by merging into a single stream the flows from five preclassifiers, 

each consisting of a 10-mm Dorr-Oliver Cyclone followed by a U.S. Bureau of Mines 

(USBM) single-stage diesel impactor with an approximately 0.8-μm cut point [Olson 

2001]. The proper flow rate of 1.7 L/min through each preclassifier was achieved by 

using identical preclassifiers and designing and using a symmetrical plenum to distribute 

the total flow rate of 8.5 L/min among the five streams. Each preclassifier assembly was 

connected to the plenum chamber by a 3-ft-long section of conductive tubing. The outlet 

of the plenum was directly connected to a stainless steel (SS) 25-mm filter holder 

containing two stacked 25-mm tissue quartz-fiber filters (Tissuquartz 2500 QAT–UP, 

Pall Corp., Ann Arbor, MI). 
26

The sampling flow rate of 8.5 L/min through the 25-mm filter was controlled by a Model 

HFC 302 mass flow controller from Teledyne, Hampton, VA. The sampling system 

incorporated a three-way valve and bypass line that allowed steady operation of the mass 

flow controller and pump while facilitating prompt starting and stopping of sampling. 

Since the sampling was done in triplicate, three identical HV sampling systems were 

used. All three flow controllers were attached to a common manifold connected to the 

suction side of a Model 0523–101Q high-volume rotary vane pump from Gast 

Manufacturing, Inc., Benton Harbor, MI. The mass flow controllers were calibrated by 

the manufacturer and checked using a Gilibrator. Identical triplicate HV sampling 

systems were used at the upstream and downstream sampling locations. 

Figure 12.—The high-volume DPM sampling train. 
27

Immediately after completion of the HV sampling for a test, each of the stacked 25-mm 

filters was removed from its holder and placed in a 47-mm polystyrene petri dish 

(Analyslide® from Pall Corp.) and identified using a self-adhesive label. These were 

shipped to NIOSH PRL and analyzed by the PRL analytical laboratory for EC content 

using NIOSH Analytical Method 5040. 

DPM Concentration Measurements With a TEOM Series 1400a 

Ambient Particulate Monitor 

Two TEOM Series 1400a ambient particulate monitors from Rupprecht & Patashnick 

Co., Albany, NY, were used to provide continual data on concentrations of total 

particulate matter (TPM) under 0.8 μm. As with the HV samplers, a 10-mm Dorr-Oliver 

Cyclone and USBM diesel impactor with a 0.8-μm cutoff were used as preclassifiers. 

The flow rate was set to 1.7 L/min. One TEOM was located at the upstream station, the 

other at the downstream sampling station. 

The TEOM measures the mass of material collected on a filter element mounted on a 

hollow tapered vibrating pedestal. As the air containing particles is drawn through a 

filter at a constant flow rate, the frequency of the oscillating pedestal decreases as the 

mass accumulates on the filter. Using frequent periodic measurements of the taperedelement frequency, the TEOM calculates the increase in mass of the sample that has 

accumulated on the filter. The concentration of TPM is calculated by dividing the 

accumulated mass by the volume of airflow across the filter during the time period over 

which the frequency change is measured. 

The flow through the instrument is maintained at a constant volumetric rate by a mass 

flow controller. The flow is corrected for temperature and barometric pressure. Internal 

temperatures in the instrument are controlled in order to minimize the effects of ambient 

temperature. In order to prevent condensation and ensure that the sample filter always 

collects particulates under similar conditions, the intake to the tapered element is heated 

and the sampling stream through the filter is maintained at 50 °C. 

The TEOM filter mass and average ambient concentrations of TPM were recorded every 

10 s. The reported TPM concentration for each test was obtained from the net gain in 

mass that occurred over the same time period as that of the HV sampling for that test. 

Measurement of Size Distribution and Particle Number Concentrations 

Using a Scanning Mobility Particle Sizer 

The scanning mobility particle sizer (SMPS) Model 3936 from TSI, Inc., St. Paul, MN, 

consisting of a Model 3080L electrostatic classifier and a Model 3025A condensation 

particle counter (CPC), was used periodically at the downstream sampling station to 

measure the size distribution and number of particles in the size range of 10–392 nm. 

The SMPS classifier was set up with a sheath airflow of 6.0 L/min and a sample flow rate 

of 0.6 L/min. At the established flow rate used, the inlet impactor had a cutoff point of 
28

0.46 μm. After the classifier, the monodispersed aerosol went to the CPC. The CPC was 

operated in high-flow mode to minimize diffusion losses. The sampling was performed 

using a 90-s up-scan and a 15-s down-scan. The instrument was operated using a 

dedicated laptop computer and Aerosol Instrument Manager Software (TSI, Inc., St. Paul, 

MN). 

Although the vehicle duty cycles used were transient, the resulting aerosol distributions 

in the mine air were made quasisteady by the nature of the duty cycle and movement of 

the vehicles relative to the ventilation air. For the purpose of assessing the effects of a 

control technology on size distribution and particle number concentrations of aerosols in 

mine air, the aerosol analysis was performed only on a set of SMPS measurements that 

were obtained during one element in the duty cycle, i.e., while the test vehicle was 

performing the portion of the duty cycle at the downstream load/dump point—a point 

closest to the downstream sampling station and the SMPS. 

The distributions and particle number concentrations obtained during other portions of 

the duty cycle were found to be extremely dependent on the position of the vehicles 

relative to the instrument. 

Concentration of CO, NO, and NO2 Measured by an Industrial Scientific iTX 

Multigas Monitor 

The ambient concentrations of CO, NO, and NO2 were measured at the upstream, 

downstream, and on-vehicle sampling locations using three iTX multigas monitors from 

Industrial Scientific, Oakdale, PA. One of the iTX multigas monitors was dedicated to 

each sampling location for the duration of the isolated zone testing. The iTX is a 

diffusion gas monitor using electrochemical cell technology. The instrument 

continuously monitors and simultaneously displays all gases sampled. The monitor’s 

logging function was used to store the 10-s average ambient concentration of each gas 

over the test period. These data were used to obtain the average concentration for each 

gas over the HV sampling period. 

The iTX gas monitors were calibrated with certified concentrations of Industrial 

Scientific-branded calibration gases prior to and upon completion of isolated zone testing. 

Each iTX was checked between the tests by coupling it to the iTX DS1000 Docking 

Station. The iTX DS1000 Docking Station is an automated instrument management 

system that consists of a master control and PC interface station. The Docking Station 

provides automatic calibration and instrument diagnostics and maintains instrument 

database records. 

The iTX gas monitors were the only instruments removed from the isolated zone at the 

end of each test. On surface, the logged data were downloaded to a laptop computer after 

each test. 
29

Downstream Concentrations of CO and CO2 Measured 

by an Innova 1312 Photoacoustic Multigas Monitor 

The ambient concentrations of CO and CO2 at the downstream sampling station were 

measured by an Innova 1312 Photoacoustic Multigas Monitor (Innova AirTech 

Instruments A/S, Nærum, Denmark). The Innova 1312 uses a photoacoustic infrared 

detection method and has a limit of detection in the parts-per-billion range. During a gas 

concentration measurement, a sample of air is drawn into the analysis cell within the 

instrument. The cell is then sealed off, and a pulsating (chopped) beam of infrared light 

is sent into the cell after passing through an optical filter that passes only that portion of 

the infrared spectrum specific to one of the gases of interest. If that gas is in the cell, 

it absorbs the infrared energy and heats up, creating a pressure pulse in step with the 

pulsing infrared light. The intensity of the pressure pulses increases with increasing gas 

concentration. The pulses are measured by microphones mounted within the cell and 

electronically processed into a gas concentration. Several filters are mounted on a wheel 

and used in turn to analyze for the different gases, including water vapor, which provides 

needed water vapor correction to the other gases. 

The instrument was calibrated by the manufacturer, and the calibration was checked 

before the study. The prevailing background CO2 concentration was determined using a 

12-hr measurement taken overnight when there were no diesel-powered vehicles in the 

zone. During each of the tests, the concentrations of CO and CO2 were measured at the 

downstream sampling station and stored into the instrument’s memory approximately 

every 62 s. The stored values were downloaded to a laptop computer at the conclusion of 

every test. The reported values for each test are the average of the logged data over the 

time period of the HV sampling for that test. 

Measurements of Exhaust Temperature and Engine Back Pressure 

A MiniLogger portable data logging system from Logic Beach, Inc., La Mesa, CA, was 

temporarily attached to a test vehicle to gather exhaust temperatures and exhaust back 

pressures during the test run. The exhaust temperature was measured using a Model 

KMQSS–125G–6, K-type thermocouple from Omega Engineering, Inc., Stamford, CT. 

The engine back pressure was measured using a Kavlico Model P356 differential 

pressure sensor from Kavlico Corp., Moorpark, CA. The output from the thermocouples 

and pressure sensors were sampled every 2 s and the average logged every 10 s. The data 

logger was programmed using HyperWare software supplied with the logger. 

Measurement of Ambient Temperature and Barometric Pressure 

The ambient temperature and barometric pressure were measured and recorded by the 

TEOM 1400a.
30

Measurements of Ventilation Rates 

Air velocities in the isolated zone were measured continuously during the tests at the 

approximate center of the drift at the downstream sampling station (Figure 13) using an 

Anemosonic UA6 digital ultrasonic anemometer from Airflow Developments Ltd., 

High Wycombe, United Kingdom. The anemometer sensor was located in the center of 

the steel grid supporting the DPM samplers. A MiniLogger was programmed to sample 

the output of the anemometer every 2 s, calculate a five-sample average, and store the 

result into memory. The memory was downloaded to a laptop computer at the conclusion 

of a test. The average air velocity for a test was computed by averaging the logged data 

over the HV sampling times for that test. The average velocity was converted to air 

quantity by multiplying it by the cross-sectional area at the anemometer location. 

Since the ventilation quantity was different for each test, the contaminant concentrations 

measured for each test had to be corrected to a common air quantity in order to determine 

the effects of the control technology by inter-test comparison. Since no comparison was 

to be made when different test engines were used, the common VR chosen for a set of 

tests using a particular engine was the MSHA nameplate VR assigned to that engine. The 

MSHA nameplate VR is the quantity of ventilation air needed to maintain a concentration 

of CO, CO2, NO, or NO2 in mine air below its corresponding 1973 ACGIH TLV values. 

This ventilation rate is calculated from the emissions of the aforementioned gases 

determined while the engine is operated over eight modes of ISO 8178 test cycle for offroad diesel engines. Normalizing the results with respect to MSHA VR provides some 

context for interpreting the contaminant concentrations, although metal mines, including 

the SMC Nye Mine, are not required to provide this quantity of ventilation air in their 

workings. 
31

Figure 13.—Downstream sampling station showing instrumentation and grid supporting 

DPM samplers, anemometer, and iTX gas monitor. 

Analysis of Samples Collected Using Standard and High-volume Methods 

The samples that were collected on quartz-fiber filters, using standard and HV sampling 

procedures, were analyzed by the NIOSH PRL analytical laboratory for EC content using 

NIOSH Analytical Method 5040 [Schlecht and O’Connor 2003; Birch and Cary 1996]. 

The analysis was performed following the procedure described for the carbon analyzer 

from Sunset Laboratories, Forest Grove, OR. A blank (heat-treated quartz-fiber filter) 

and sugar standard were run daily before analysis of the samples. 

Calibrated punches were used to remove a section from the exposed area of a filter. The 

punch with a cutout area of 0.72 cm2

 was used for heavily loaded samples, while a punch 

with an area of 1.5 cm2 was used for other samples. The cutout is placed into the oven of 

the carbon analyzer and analyzed following the procedure described in the NIOSH 

Manual of Analytical Methods [Schlecht and O’Connor 2003] and by Birch and Cary 

[1996]. 

NIOSH Analytical Method 5040 analyzes for OC and EC in two different stages. In the 

first stage, the OC evolves as the instrument ramps the oven temperature up over four 

progressively higher temperature steps in a pure helium (He) atmosphere. The 

temperature steps for the OC portion were set to 200, 450, 650, and 870 °C. The duration 

at each temperature step was longer than used typically so that the carbon peaks could be 
32

fully resolved at each temperature step. The EC does not evolve in the pure He 

atmosphere. The evolved OC is oxidized to CO2, reduced to methane (CH4), and finally 

measured using a flame ionization detector. 

In the second stage, the EC is measured by reducing the oven temperature to about 

600 °C and then raising the temperature to around 900 °C in a He/O2 atmosphere where 

the oxygen, now present, reacts quantitatively with the EC to form CO2. The EC is then 

measured in the same way as the OC. NIOSH Analytical Method 5040 also corrects for 

pyrolysis of OC and carbonates. 

Sampling and Measurement Methodology 

Three sampling locations were established for this isolated zone study. The upstream 

sampling station was located approximately 90 m (295 ft) upstream of the upstream 

load/dump point. The downstream sampling station was established approximately 

140 m (459 ft) downstream of the downstream load/dump point and 60 m (197 ft) 

upstream of the ventilation doors. The third sampling location was located on the test 

vehicle. 

Upstream Sampling Station 

The following methods were used to determine contaminant concentrations at the 

upstream station: 

1. A standard sampling procedure was used to collect DPM samples for EC. 

2. An HV sampling procedure was used to collect DPM samples for EC. 

3. A TEOM Series 1400a was used for real-time measurements of TPM under 

0.8-μm aerodynamic size. 

4. An iTX multigas monitor logged 10-s average concentrations of CO, NO, and 

NO2. 

Downstream Sampling Station 

The following methods were used to determine concentrations of the particulate matter at 

the downstream station: 

1. The standard sampling procedure was used to collect DPM samples for EC. 

2. The HV sampling procedure was used to collect DPM samples for EC. 

3. The TEOM Series 1400a was used for real-time measurements of TPM under 

0.8-μm aerodynamic size. 

4. The SMPS was used to measure size distribution and particle number concentrations of aerosols. 
33

The following instrumentation was used to measure concentrations of the selected gases 

at the downstream station: 

1. The iTX Multigas Monitor was used for real-time display and logging of 

concentrations of CO, NO, and NO2. 

2. The Innova 1312 Photoacoustic Multigas Monitor was used for real-time 

measurements of concentrations of carbon, CO, and CO2. 

The distribution of the standard and HV samplers across the upstream and downstream 

stations is shown in Figure 14. 

 Figure 14.—Distribution of samplers across sampling station showing 

the locations of the high-volume sampling heads (light) and three standard 

samplers (dark) (not to scale). 
34

On-vehicle Sampling Location 

The on-vehicle sampling location was approximately 0.6 m (2 ft) from the operator. At 

this sampling location, the standard sampling procedure was used to collect particulate 

samples for carbon analysis. An iTX multigas monitor was incorporated in this sampling 

station. It was used for real-time monitoring and logging of concentrations of CO, NO, 

and NO2. 

Sampling Strategy 

The following procedure was established for sampling in the isolated zone: 

1. All direct-reading and logging instrumentation was verified as working and 

logging started as appropriate. 

2. The test vehicle was brought to the fueling station prior to the test and topped off 

with fuel. While the vehicle was being fueled, the operator was briefed on the 

details of the test protocol and instructed on the duty cycle to be used for the test. 

3. After the fueling was finished, the operator returned to the upstream load/dump 

point and starting from there performed two full warmup cycles. 

4. At the end of the second warmup cycle, the vehicle was stopped at the upstream 

load/dump point, the time was noted, and all particulate matter samplers at all 

three sampling stations were turned on. At this time, the test officially began. 

5. The objective was to collect at least 30 μg of EC on the HV sampling filters used 

at the downstream sampling station. The length of the tests was estimated on the 

basis of the real-time measurements of particulate concentrations at the 

downstream sampling station using the TEOM 1400a. When enough material 

was collected on the HV samplers, they were stopped at both sampling stations. 

If the standard sampling continued, when enough material was collected on the 

standard downstream samplers, the pumps at the downstream, the vehicle, and the 

upstream sampling stations were stopped and the test was terminated. 

6. The actual sampling on and off times and total sampling times for the standard 

and HV samples were recorded. 

7. The sampling flow rates were checked daily and, if necessary, the pumps were 

recalibrated. 

The measurements with real-time instrumentation were initiated prior to the beginning of 

the DPM sampling period and stopped after the end of the sampling period for the 

standard samplers, which usually continued beyond the sampling period for the highvolume samplers. 
35

Calculation of the Effects of Control Technologies 

The effects of each of the tested control technologies were determined by comparing the 

results of tests with and without control technologies. The contributions of the test 

vehicles to the concentration of each contaminant were calculated assuming that the mass 

of contaminant at the downstream sampling station is equal to the sum of the mass of 

contaminant emitted by the engine and the corresponding mass of contaminant that 

entered the isolated zone upstream of the test zone. In order to allow a direct comparison 

of the results between the tests within each test group, the measured concentrations were 

corrected for variations that occurred between tests due to the nature of the test 

environment and methods. Differences in ventilation rates and ability of the operator to 

replicate the duty cycle over several tests being compared were assumed to be major 

factors influencing the results. The results of gas and DPM measurements were corrected 

for the effects of ventilation rates by adjusting them to a common average VR. The EC 

results were also adjusted for the combined effects of VRs and duty cycles by 

normalizing those to an average level of CO2. These methods are discussed below. 

Net Contributions and Relative Effects of the Tested Control Technologies: 

The VR Adjustment Procedure 

The average VR was calculated for each test using results of VR measurements made for 

each test run at the downwind sampling station. The measured concentrations were 

adjusted to a common VR, which was the nameplate VR established by MSHA for the 

particular test engine. 

One should note that concentrations of contaminants at the downstream sampling station 

were VR-dependent, while concentrations of contaminants at the upstream sampling 

station were VR-independent. 

The measured concentrations (ci) were corrected to the VR-adjusted concentrations (ci,VR) 

using as reference MSHA VR (VRj, MSHA) for the engine used in that particular group of 

tests. This relation is given in Equation 1, 

VRC

m

g c

s

m VR

s

m VR

m

g c

m

g c i

j MSHA

i

i VR = i × = [ ] ×

[ ]

[ ]

[ ] [ ] 3 3

,

3

, 3 3 Equation 1 

where VRC is the VR coefficient, which is defined as the ratio of the average VRi for the 

test and the MSHA nameplate ventilation for the test engine used. 

The net contribution of the tested vehicle/technology configuration to the air 

concentrations of pollutants (Ci) was calculated by subtracting the concentrations 

measured at the upstream sampling station (ci,UP) from the VR-adjusted concentrations at 

the downstream sampling station (ci, VR,DOWN): 
36

[ ] [ ] [ ] 3 , , 3 , 3 m

g c

m

g c

m

g Ci = i VR DOWN − i UP Equation 2 

Similarly, the net contribution of the tested configuration to the exposure of the operator 

was estimated by subtracting the upstream concentrations from the ventilation-adjusted 

concentrations measured at the vehicle. 

In cases where the analysis of the upstream data showed that the upstream concentrations 

of the measured pollutant were below the detection limit of the method or 

instrumentation, the background concentrations were assumed to be negligible. 

The net contributions were then used to calculate the relative effects of the tested control 

technologies on the concentrations of the monitored pollutants: 

100

[ ]

[ ]

ControlTechnologyEffect (%) 1

3

3

×

⎟

⎟

⎟

⎟

⎠

⎞

⎜

⎜

⎜

⎜

⎝

⎛

= −

m

g C

m

g C

i BL

i

 Equation 3 

where Ci is the net contribution of the vehicle to the air concentrations of pollutant for the 

control technology case and Ci BL is the net contribution of the vehicle to the air 

concentrations of pollutant for the baseline case. 

Net Contributions and Relative Effects of the Tested Control Technologies: 

the CO2 Adjustment Procedure 

Under established test conditions, quantifying actual work done by the vehicle/engine 

over the duty cycle would be rather complicated. Therefore, the alternative approach 

based on measuring the average net CO2 emissions over the test cycle was used to assess 

the relative work performed by vehicles. This concept originated in contract work by 

Michigan Technological University for the USBM in the early 1980s [Schnakenberg 

et al. 1986; Johnson and Carlson 1985, 1986]. The assumption is that the emissions of a 

particular contaminant (gases or DPM), when divided by the average fuel used, would be 

relatively constant over a particular duty cycle for minor variations in that cycle. Since 

CO2 emissions are directly proportional to the amount of fuel used, the ratio of the 

average gas or DPM emissions to the average CO2 emissions can be assumed to be 

reasonably constant. Furthermore, this ratio holds for the resulting concentrations of 

diesel pollutants in the ambient air and is wholly independent of the prevailing ventilation 

rate since the contaminant and CO2 are diluted equally. On the other hand, when the 

average CO2 concentrations between two tests to be compared are significantly different 

and this difference is not attributable to ventilation, one should suspect that the duty 

cycles were executed differently. The relationship can be used only in the cases where 

the control technology does not alter the concentration of CO2 in exhaust. Aftertreatment 

devices such as DPFs and DOCs are designed to affect the emissions of CO, HCs, EC, 

and particulate matter, but they do not significantly affect CO2 emissions. Those devices 
37

also do not significantly affect total emissions of nitric oxides, but they affect the ratio 

between NO and NO2 emissions. 

The concentrations of CO2 were measured and recorded in real time at the downstream 

sampling location. In this study, the average net CO2 concentrations (measured CO2

minus the background CO2) over the sampling periods were used to normalize the 

corresponding average concentrations of EC collected using HV and standard sampling 

methods. 

Equation 4 defines a relative EC concentration (CECCO2 ) per concentration of CO2 (CCO2 ). 

This ratio is engine-specific and duty cycle-specific. 

[ ]

[ ]

[ ]

2

2

3 3

C ppm

m

g C

ppm

m

g

C

CO

EC

ECCO

μ μ

= Equation 4 

The effects of control technologies on net concentrations of EC were calculated using 

corresponding net CO2-normalized concentrations measured for the control technology 

(CT) case (C[ECCO2]CT ) and the baseline (BL) case (C[ECCO2]BL ): 

100%

C

C

Control Technology Effect (%) 1

BL [ECCO ]

CT [ECCO ]

2

2

× ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛ = − Equation 5 

EXHAUST EMISSION TESTING 

The isolated zone tests were complemented with a series of DPM and gaseous emissions 

measurements performed directly from the exhaust systems of the tested vehicles. The 

objective of the exhaust pipe emission measurements was to verify the performance of 

the tested engines and control technologies used in the isolated zone study. The 

measurements were made for the majority of evaluated configurations. This part of the 

study was a joint effort between NIOSH and the SMC maintenance department. The 

tests took place in the main surface repair facility at Nye Mine. 

Engine Operating Conditions 

The exhaust pipe emissions were obtained while each test vehicle was parked in the shop, 

and the engine was operated under three steady-state conditions: 

1. Torque converter stall (TCS), stall engine speed at full throttle; 

2. High idle (HI), rated engine speed/full throttle, no load; and 

3. Low idle (LI), idle engine speed, no load. 
38

These conditions were selected as the only repeatable and safe conditions suitable for 

testing an engine without using a chassis dynamometer. 

TCS was assumed to be the most suitable method to significantly load engines that are 

coupled with an automatic transmission through a torque converter. This mode can be 

achieved by applying the vehicle’s brakes and loading the engine by making the torque 

converter work against a transmission that is engaged in the highest gear. Under such 

conditions, the energy produced by the engine is converted into heat and dissipated in the 

torque converter system. The duration of the TCS test is limited by the fact that the 

torque converter cooling system is usually not capable of dissipating the energy generated 

for an extended period of time. Permanent damage of the torque converter was avoided 

by stopping any TCS test before the torque converter temperature exceeded a maximum 

allowed temperature. Because the TCS condition is quite reproducible and results in the 

highest engine load and consequently the highest DPM and gaseous emissions of the 

three possible repeatable conditions for testing vehicles under field conditions, it was 

considered to be the most representative for engine and control technology effects testing. 

At HI mode, brakes were applied, the transmission was placed in neutral, and the engine 

speed was maintained at rated speed. Typically, DPM emissions for this mode are 

substantially lower than those found at TCS conditions. 

At LI mode, brakes were applied, the transmission was placed in neutral, and the engine 

speed was maintained at idle. Again, DPM emissions for this mode typically are 

substantially lower than those at TCS and HI mode. 

Equipment, Instrumentation, and Methods for Measurement of 

Exhaust Pipe Emissions 

The effects of the aftertreatment technologies on the particulate matter and gaseous 

emissions were determined by comparing emissions obtained from a sampling port 

located upstream to those obtained from either a sampling port downstream of the system 

or tailpipe outlet. In the case of tests involving fuel formulations, the emissions were 

obtained upstream of any aftertreatment device. The effects were determined by 

comparing results of the similar tests conducted with different fuel formulations. 

The inlet side of each of the tested DPF systems was equipped with at least two 13-mm 

(0.5-in) NPT ports made with SS pipe couplings that were welded over a 13-mm (0.5-in) 

or 19-mm (0.75-in) hole in the exhaust pipe. 

The tailpipe emissions were measured independently by NIOSH researchers and by SMC 

Nye Mine maintenance personnel. All emissions measured by NIOSH were repeated at 

least three times for each test condition. The test procedures remained uniform across all 

engine/vehicle configurations. NIOSH used the following methods and instrumentation 

for measuring DPM and gaseous emissions in the exhaust systems of the test vehicles: 
39

1. An ECOM Model KL portable emissions analyzer from ECOM America Ltd., 

Norcross, GA, was used to measure exhaust pipe concentrations of O2, CO, NO, 

and NO2. 

2. The same portable emissions analyzer was used to collect a smoke sample from 

exhaust pipe for Bacharach smoke number analysis and used as a means to obtain 

DPM samples on tissue quartz for carbon analysis. 

SMC Nye Mine maintenance personnel used an Enerac 400 EMS Micro Emissions 

Monitoring System from Enerac, Inc., Westbury, NY, to measure tailpipe concentrations 

of O2, CO, NO, and NO2 following their own test protocol for collecting data 

continuously through three consecutive steady-state test conditions (LI, HI, and TCS) and 

the transient conditions in between. 

Both the ECOM KL and the Enerac 400 used electrochemical sensors to measure 

concentrations of O2, CO, NO, and NO2. The instruments calculated the CO2 emissions 

from the measured O2 concentration and the fuel type used. The ECOM combustion 

analyzer also performs a smoke analysis. A special filter paper is inserted into a slot in 

the exhaust probe through which the ECOM draws a 1.6-L sample of exhaust. The 

particulate matter collected on the paper filter generates a dark spot. The darkness of the 

spot is compared with the 0-to-9 gray scale provided by the manufacturer. The number 

assigned to the darkness of the sample is also known as the Bacharach smoke number. 

The ECOM smoke sampling procedure was used to obtain a DPM sample on tissue 

quartz for carbon analysis using NIOSH Analytical Method 5040. 
40

RESULTS AND DISCUSSION 

RESULTS OF ISOLATED ZONE TESTS 

Ventilation Rates 

The VR was measured continuously during each test at the downstream sampling station 

using a digital ultrasonic anemometer fixed to the center of the grid holding the DPM 

samplers. The charts of the ventilation logs are presented in Figures 15–19. 

0

2

4

6

8

10

12

14

16

18

0 2000 4000 6000 8000 10000 12000

Time [s]

Ventilation rate [m^3/s]

Baseline Engelhard DPX

 

Figure 15.—Ventilation rates for the tests involving #92128. 
41

0

1

2

3

4

5

6

7

0 2000 4000 6000 8000 10000 12000 14000

Time [s]

Ventilation rate [m^3/s]

Baseline + CDT CleanAir + CDT

Figure 16.—Ventilation rates for the tests involving #92133. 

0

5

10

15

20

25

30

0 5000 10000 15000 20000 25000

Time [s]

Ventilation rate [m^3/s]

Baseline 1 Baseline 2 DCL BlueSky Donaldson

Figure 17.—Ventilation rates for the tests involving #92506. 
42

0

2

4

6

8

10

12

14

16

18

0 1000 2000 3000 4000 5000 6000

Time [s]

Ventilation rate [m^3/s]

Baseline Baseline + PTX ECS Cattrap Biodiesel B20 + PTX Biodiesel B50 + PTX

Figure 18.—Ventilation rates for the tests involving #92526. 

 

0

5

10

15

20

25

30

0 1000 2000 3000 4000 5000 6000 7000 8000

Time [s]

Ventilation rate [m^3/s]

Baseline, #1 diesel Baseline, #2 diesel DCL MineX

Figure 19.—Ventilation rates for the tests involving #99942. 
43

As noted previously, all ventilation data (downstream) and gaseous concentration data 

(upstream and downstream) used for each test (i.e., the test data) are averages of the 

logged data over the time period for the sampling of the HV samplers or standard 

samplers for that test. The ventilation rate coefficient (VRC) and the normalized net test 

vehicle contribution to the CO2 concentration for each test are summarized in Table 6. 

Table 6.—Ventilation rate coefficients and normalized contributions 

of the test vehicles/configurations to CO2 concentrations 

Ventilation rate coefficient 

(VRC) 

Contribution of the 

vehicles to CO2

concentrations, ppm 

Test type Date 

High-volume 

sampling 

period 

Standard 

sampling 

period 

Maximum 

Average 

Standard 

Period 

#92128 Haul Truck, MSHA VR = 5.66 m3/s (12,000 ft3/min) 

Baseline 5/26/2003 2.77 2.77 3,432 2,504 

Engelhard DPX 5/26/2003 2.71 2.71 3,391 2,314 

#92133 Haul Truck, MSHA VR = 5.66 m3/s (12,000 ft3/min) 

Baseline + CDT 5/22/2003 0.82 0.82 1,361 1,232 

CleanAIR + CDT 5/22/2003 0.82 0.82 1,487 1,334 

#92506 LHD, MSHA VR = 5.43 m3/s (11,500 ft3/min) 

Baseline 1 5/23/2003 4.56 4.62 5,866 1,694 

Baseline 2 5/23/2003 4.55 4.61 5,472 1,652 

DCL BlueSky 5/21/2003 0.31 0.31 715 553 

Donaldson 5/23/2003 1.19 1.19 1,677 1,417 

#92526 LHD, MSHA VR = 4.72 m3/s (10,000 ft3/min) 

Baseline 5/27/2003 2.89 2.91 7,418 3,289 

Baseline + PTX 5/27/2003 2.93 2.95 7,220 3,515 

ECS Cattrap 5/24/2003 1.27 1.27 3,291 2,404 

Biodiesel B20 + PTX 5/28/2003 2.84 2.87 7,048 3,414 

Biodiesel B50 +PTX 5/28/2003 2.93 2.95 7,220 3,467 

#99942 LHD, MSHA VR = 7.08 m3/s (15,000 ft3/min) 

Baseline, #1 diesel 5/29/2003 3.41 3.46 8,338 2,539 

Baseline, #2 diesel 5/30/2003 3.34 3.35 8,626 2,546 

DCL MINE–X 5/29/2003 3.33 3.33 8,387 2,482 
44

The data presented in Table 6 suggest that isolated zone tests can be divided into two 

groups with respect to the VR that prevailed during the tests. The first group consists of 

five tests conducted during the first 4 days of the study (5/21/2003 through 5/24/2003) in 

which the VR was maintained below or in the neighborhood of the MSHA VR for the 

particular test engine (see Figures 16–18 and Table 6 where VRC is about 1 or below). 

The VRs for the rest of the tests were significantly higher than the MSHA engine 

nameplate VRs for the test engines (see Figures 15, 17, 18, and 19, and Table 6). 

As alluded to earlier, it can be expected that the net contribution to CO2 concentrations 

for several tests using the same engine over the same duty cycle should be about equal 

when normalized for VR and when CO2 is unaffected by the control technology. It 

should be noted that the tailpipe emission results verified that none of the tested control 

technologies had a significant effect on the CO2 emissions. Thus, one can use this 

knowledge to check on the validity of any particular test. 

An examination of the vehicle contribution to the normalized CO2 concentrations shown 

in Table 6 reveals that the VR-normalized CO2 concentrations for the tests conducted 

while the VR was maintained in the neighborhood of the MSHA VR or below (VRC 

about 1 or below in Table 6) are significantly lower than those for the rest of the tests. 

One would expect that the VR-normalized CO2 contributions for the tests involving the 

DCL BlueSky and the Donaldson filtration systems on LHD #92506 would be equal to 

those of the other tests using LHD #92506. Similar expectations apply for the test 

involving the ECS Cattrap DPF system on LHD #92626. 

Likewise, similar VR-normalized CO2 levels would be expected for the baselines for haul 

trucks #92128 and #92133 because their tailpipe CO2 emissions (see Table 16) were 

almost identical at each test condition and because they were powered with similar 

engines (Deutz BF6M1013FC and BF6M1013ECP). However, the VR-normalized CO2

concentrations during the tests for those vehicles were significantly different. The 

observed concentrations were twice as high for #92128 compared to #92133 (see 

Table 6). 

Although the reason for these discrepancies was not clear at the time, the protocol was 

altered to increase the ventilation rate for the second week of testing primarily to reduce 

the ventilation rate fluctuations observed during the earlier tests with low ventilation 

rates.8

Since neither a clear explanation nor method for correcting the data obtained at the low 

ventilation rates was at hand, only the results of the tests in which the VR was maintained 

significantly above the MSHA VRs are presented. The exception is the two tests 

conducted with haul truck #92133. Since the ventilation rates (Figure 16) and CO2

 

8

At the time, the researchers suspected that ventilation air was leaking from the isolated zone midway 

between the load/dump points. The leak was verified the following year during another isolated zone 

study. Opening the ventilation doors both reduced the differential pressure driving the leak, reducing its 

volume flow, and increased the main airflow so that the effect of the remaining leak on contaminant 

concentrations was not significant. 
45

contributions (Table 6) were almost identical and fairly constant during those two tests, 

we believe that the results from those tests can be used to compare the relative effects of 

the CleanAIR Systems DPF system on EC concentrations in mine air. 

Effects of Control Technologies on EC Concentrations 

The results of the EC analysis performed on the samples collected using the high-volume 

samplers are presented in Tables 7–8. The net contributions to the EC concentrations in 

Table 7 are adjusted (normalized) to those that would be measured if the engine-specific 

MSHA nameplate VR had been maintained. Those data can be used to estimate the 

potential contributions of control technologies to the concentration of EC at any given air 

quantity. Table 8 presents the results of the same EC analysis, but normalized to the net 

CO2 concentration found during the test. The EC reduction efficiencies for VR- and 

CO2-normalized results were found to be nearly identical, except for the two cases in 

which the effects of the control were less than 10%, i.e., where the observed effect was 

on the same order as the error in measurement. 

Table 7.—Effects of control technologies on VR-normalized net EC concentrations 

Average contributions to 

Test type EC concentrations 

μg/m3

 CV, % 

Reductions, % 

#92128 Haul Truck, MSHA VR = 5.66 m3/s (12,000 ft3/min) 

Baseline 1,182 5.3 

Engelhard DPX 51 3.2 96 

#92133 Haul Truck, MSHA VR = 5.66 m3/s (12,000 ft3/min) 

Baseline + CDT 1,038 10.6 

CleanAIR + CDT 15 5.3 99 

#92506 LHD, MSHA VR = 5.43 m3/s (11,500 ft3/min) 

Baseline 1 938 3.0 

Baseline 2 1,051 6.6 −12 

#92526 LHD, MSHA VR = 4.72 m3/s (10,000 ft3/min) 

Baseline 1,328 1.6 

Baseline + PTX 1,365 2.0 −3 

Biodiesel B20 + PTX 1,015 4.7 26 

Biodiesel B50 + PTX 703 4.3 48 

#99942 LHD, MSHA VR = 7.08 m3/s (15,000 ft3/min) 

Baseline, #1 diesel 1,112 7.7 

Baseline, #2 diesel 1,222 4.0 −10 

DCL MINE–X 149 2.6 88 

The coefficient of variation (CV) was used to measure the agreement among the triplicate 

HV samples presented in Table 7. The uncertainties in sampling volume and the 

analytical error inherent to NIOSH Analytical Method 5040 were the major parameters 
46

that contributed to the CV. The CVs for the elemental carbon results for the high-volume 

samplers obtained in this study ranged from 1.6% to 10.6%, with a median of 4.3% and a 

mean of 4.7%. 

As mentioned previously, results of several of the tests were not further analyzed because 

of unexplainably low vehicle contributions to CO2 concentrations found for the tests 

conducted at low VRs. However, for the two tests on vehicle #92133, although the VRs 

were low, they were nearly identical, resulting in identical CO2 levels for both baseline 

and tests run with the DPF system. As a result of this consistency, the data for these tests 

were included in this report. 

Table 8.—Effects of control technologies on CO2-normalized net EC concentrations 

Test type 

Average 

contributions to 

EC 

concentrations, 

μg/m3

Average 

contributions to 

CO2 

concentrations, 

ppm 

CECCO2

μg/m3

/ppm Reductions, % 

#92128 Haul Truck, MSHA VR = 5.66 m3/s (12,000 ft3/min) 

Baseline 427 878 0.486 

Engelhard DPX 18 855 0.021 96 

#92133 Haul Truck, MSHA VR = 5.66 m3/s (12,000 ft3/min) 

Baseline + CDT 1,265 1,501 0.843 

CleanAIR + CDT 18 1,618 0.011 99 

#92506 LHD, MSHA VR = 5.43 m3/s (11,500 ft3/min) 

Baseline 1 206 370 0.555 

Baseline 2 230 368 0.625 −13 

#92526 LHD, MSHA VR = 4.72 m3/s (10,000 ft3/min) 

Baseline 459 1,082 0.424 

Baseline + PTX 465 1,153 0.403 5 

Biodiesel B20 + 

PTX 

357 1,126 0.317 21 

Biodiesel B50 + 

PTX 

239 1,133 0.211 48 

#99942 LHD, MSHA VR = 7.08 m3/s (15,000 ft3/min) 

Baseline, #1 diesel 325 752 0.432 

Baseline, #2 diesel 366 814 0.449 −4 

DCL MINE–X 44 745 0.059 87 

Due to an unfortunate mistake in supplying fuel for a number of the tests, the two tests 

using LHD #92506, which were designed specifically to show the effects of the fuel 

formulation (#1 vs. #2 diesel) on the emissions, actually used nearly the same blend of 

diesel fuel (see Table 4), 90% #2 and 100% #2, respectively. These tests can be 

considered as an opportunity to examine repeatability of the test method. As can be 

determined from the preceding tables, the ability to replicate a test was about ±6%–7%. 
47

Effects of Control Technologies on TPM 

This section summarizes the results of the TPM measurements conducted at the upstream 

and downstream sampling stations using two TEOM 1400a ambient particulate monitors. 

A submicron preclassifier described earlier eliminated all particles with an average 

aerodynamic diameter larger than approximately 0.8 μm. The preclassifier was identical 

to that used for the HV samplers for EC, allowing a comparison of EC with TPM. 

The observed concentrations of TPM measured at the upstream sampling station were 

negligible and therefore not used in this analysis. The VR-normalized TPM 

concentrations measured at the downstream monitoring station are presented in Table 9. 

Table 9.—Concentrations of TPM under 0.8 μm at the downstream sampling station 

Concentrations of TPM, 

μg/m3 Reductions, % Test Type 

Avg. Max. Avg. 

#92128 Haul Truck, MSHA VR = 5.66 m3/s (12,000 ft3/min) 

Baseline 1,343.9 1,536.3 — 

Engelhard DPX 341.7 411.6 75% 

#92506 LHD, MSHA VR = 5.43 m3/s (11,500 ft3/min) 

Baseline 1 3,964.1 7,313.2 — 

Baseline 2 N/A N/A — 

#92526 LHD, MSHA VR = 4.72 m3/s (10,000 ft3/min) 

Baseline 1,631.9 2,083.0 — 

Baseline + PTX 1,874.6 2,324.6 — 

Biodiesel B20 + PTX 1,698.8 2,084.8 9% 

Biodiesel B50 + PTX 1,416.6 1,800.7 24% 

#99942 LHD, MSHA VR = 7.08 m3/s (15,000 ft3/min) 

Baseline, #1 diesel 1,433.6 2,140.2 — 

Baseline, #2 diesel 1,735.1 2,739.2 −21% 

DCL MINE–X 369.6 588.1 74% 

The effects of the control technologies on TPM concentrations were expressed in terms 

of the percent reductions that were calculated using VR-normalized average values. 

These results show that both the Engelhard DPX and DCL MINE–X DPF systems 

reduced the TPM in the mine air by approximately 75%. These reductions were lower 

than those for EC shown in Table 7 (96% and 88%, respectively). A similar statement 

can be made for the tests of the biodiesel blends, which incorporated an Engelhard PTX 

DOC. However, the differences can be attributed to the fact that the TEOM measures 

total particulate mass while carbon analysis accounts only for the EC fraction of total 

particulate mass. 

The plot shown in Figure 20 presents the time trace of concentrations measured by the 

TEOM during the baseline test of LHD #99942. The peaks and valleys shown on this 
48

plot are due in part to the varying emission rates of the vehicle over the duty cycle, in part 

to fluctuations in VR, and in part to the relative position of the vehicle to the downstream 

sampling location. The time traces of the other measured emissions show similar trends. 

The near real-time TEOM TPM concentration data were used during the test to estimate 

the mass of DPM collected on the filters used in the HV and standard sampling methods 

for carbon analysis and thus to ensure that the sampling continued long enough to collect 

sufficient sample mass for accurate analysis without unduly prolonging the test. 

0

500

1000

1500

2000

2500

0 1000 2000 3000 4000 5000 6000 7000 8000

Time [s]

Concentration [ug/m^3]

 Figure 20.—TPM concentrations at the downstream sampling station for the baseline 

test on LHD #99942. 

Effects of Control Technologies on Particle Size Distribution and 

Number Concentration 

This section summarizes the results of the measurements of size distributions and number 

concentrations of aerosols at the downstream sampling station. The measurements were 

performed using a Model 3936 scanning mobility particle sizer (SMPS) as described 

earlier. Only the results of the measurements made while vehicles were performing their 

duties at the downstream load/dump point in the isolated zone are presented in this report. 

The results are presented in Table 10 and Figures 21–26. The statistical parameters and 

plots for two or three typical measurements are also shown for each of the test cases. The 

geometric mean diameter (GMD) and geometric standard deviation (GSD) are supplied 

for each of those distributions. The average GMD and average total particulate number 

concentration are calculated for each set of data, with the latter normalized with respect 
49

to the MSHA VR specific for each test engine. Whereas previously the effect of a tested 

control technology has been expressed as its efficiency in reducing a contaminant 

concentration, here the effect of a tested control technology is expressed as the 

percentage of change in total particulate number concentrations with respect to the 

appropriate baselines. For most of the cases, the tests in which vehicles were operated 

with mufflers and standard fuel were considered to be the baseline cases. The exceptions 

were the tests that were conducted to assess the effects of the biodiesel blends. In these 

cases, the test conducted with the LHD #92526 equipped with a diesel oxidation catalytic 

converter and muffler was considered to be the baseline. 

Since both of the tested DPFs—the Engelhard DPX and the DCL MINE–X—show 

dramatic reductions in the number of larger particles (see Figures 21–22), it can be 

concluded that the size distribution measurements qualitatively agree with the EC and 

TPM results for those systems. The size distributions of the particles that are observed 

for the tests with filtered exhaust are characterized with significantly lower GMDs and 

higher peak number concentrations than the size distributions observed during the tests 

with unfiltered exhaust. The distributions of particles generated by vehicles equipped 

with a muffler were characterized by GMDs ranging from 64 to 87 nm (see Table 10). In 

contrast, the distributions of particles generated by vehicles equipped with DPFs were 

characterized by a GMD ranging from 35 to 45 nm (see Table 10). Additionally, a 

significant increase in the total number of particles, approximately 60%–80%, was 

evident for both cases when mufflers were replaced with DPFs (see Table 10). Since 

carbon analysis shows very low mass concentrations of EC in the samples collected 

during the same tests with filtered exhaust, it can be stipulated that those particles contain 

primarily other known constituents of DPM such as organic carbons, sulfates, and water. 

Unfortunately, since appropriate samples were not gathered, a chemical analysis of the 

DPM samples is not available to confirm this hypothesis. 
50

Table 10.—Effects of control technologies on concentration of aerosols in mine air 

Test Type GMD, 

nm GSD 

Average 

Geometric 

Mean, 

nm 

Average Total 

Particle Conc. 

at MSHA VR, 

 #/cm3 

Change in Total 

Particle Conc., % 

#92128 Haul Truck, MSHA VR = 5.66 m3/s (12,000 ft3/min) 

71.64 1.83 

Baseline 65.84 1.83 

64.35 1.90 

67.28 4.49E+06 — 

45.14 1.44 

Engelhard DPX 43.46 1.47 

42.63 1.44 

43.74 8.07E+06 79.6 

#92506 LHD, MSHA VR = 5.43 m3/s (11,500 ft3/min) 

83.75 1.63 

Baseline 1 

72.61 1.68 

78.18 1.43E+07 — 

81.34 1.66 

Baseline 2 82.02 1.66 

76.39 1.80 

79.91 1.29E+07 −9.9 

#92526 LHD, MSHA VR = 4.72 m3/s (10,000 ft3/min) 

85.05 1.68 Baseline 

86.43 1.67 

85.74 8.56E+06 — 

72.22 1.75 

Baseline + PTX 

72.59 1.74 

72.40 1.01E+07 18.2 

Biodiesel B20 + 65.83 1.66 

PTX 66.01 1.65 

65.92 1.22E+07 20.4 

Biodiesel B50 + 63.32 1.60 

PTX 60.21 1.61 

61.76 1.15E+07 14.1 

#99942 LHD, MSHA VR = 7.08 m3/s (15,000 ft3/min) 

74.41 1.64 

76.60 1.65 Baseline, 

#1 diesel 

75.24 1.65 

75.42 1.63E+07 — 

81.57 1.65 

81.68 1.63 Baseline, 

#2 diesel 

82.53 1.63 

81.93 1.71E+07 4.9 

40.70 1.58 

DCL MINE–X 35.49 1.57 

37.99 1.59 

38.06 2.61E+07 60.6 

It is important to note that the size distributions and number concentrations of aerosols in 

the observed size range are highly dependent on the ambient conditions. The formation 

of aerosols could be significantly affected by the natural cooling process occurring in the 

isolated zone and the high relative humidity that prevailed during the tests. Average 

ambient temperatures of approximately 25 °C (77 °F) were recorded at the upstream 

sampling station, and average ambient temperatures of approximately 10 °C (50 °F) were 

recorded at the downstream sampling station. The average relative humidity measured at 

the downstream station during the tests was approximately 90%. 
51

0.00E+00

5.00E+06

1.00E+07

1.50E+07

2.00E+07

2.50E+07

10 100 1000

D_p [nm]

dN/(d log D_p) [#/cm^3]

Baseline, #1 Baseline, #2 Baseline, #3

Engelhard, #1 Engelhard, #2 Engelhard, #3

Figure 21.—Size distribution of aerosols in mine air for truck #92128: the baseline case 

and Engelhard DPX DPF case (three measurements for each test). 

0.00E+00

1.00E+07

2.00E+07

3.00E+07

4.00E+07

5.00E+07

6.00E+07

10 100 1000

D_p [nm]

dN/(d log D_p) [#/cm^3]

Baseline, #1 Baseline, #2 Baseline, #3

DCL MineX, #1 DCL MineX, #2 DCL MineX, #3

Figure 22.—Size distribution of aerosols in mine air for LHD #99942: the baseline case 

and DCL MINE–X DPF case (three measurements for each). 
52

As mentioned previously, owing to an unfortunate mistake in supplying fuel for a number 

of the tests, the tests using LHD #92506 used similar blends of #2 and #1 fuel (see 

Table 4) and provided an opportunity to examine repeatability of the test method. The 

size distribution and number concentration results for these two tests showed relatively 

good agreement (see Figure 23). The results of the size distribution measurements 

(average GMD) summarized in Table 10 agree with the other particulate matter results 

obtained in this study, showing relatively good inter-test agreement. 

0.00E+00

5.00E+06

1.00E+07

1.50E+07

2.00E+07

2.50E+07

3.00E+07

3.50E+07

10 100 1000

D_p [nm]

dN/(d log D_p) [#/cm^3]

Baseline 1, #1 Baseline 1, #2 Baseline 2, #1 Baseline 2, #2 Baseline 2, #3

 Figure 23.—Size distribution of aerosols in mine air for truck #92506: the baseline 1 case 

(two measurements) and baseline 2 case (three measurements). 

The effects of the Engelhard PTX DOC on the size distribution of aerosols are apparent 

from Figure 24. The size distributions of the particles that are observed for the tests with 

the DOC are characterized with a somewhat lower GMD (72.40 vs. 85.74 nm) and higher 

peak number concentrations (1.01 × 107

 vs. 8.56 × 106 #/cm3) than the size distributions 

observed during tests with the muffler alone (see Table 10 and Figure 24). An 

approximately 18% increase in the number of particles was found when the muffler was 

replaced with a DOC and muffler combination (see Table 10). 
53

0.00E+00

2.00E+06

4.00E+06

6.00E+06

8.00E+06

1.00E+07

1.20E+07

1.40E+07

1.60E+07

1.80E+07

2.00E+07

10 100 1000

D_p [nm]

dN/(d log D_p) [#/cm^3]

Baseline, #1 Baseline, #2 Baseline + PTX, #1 Baseline + PTX, #2

 Figure 24.—Size distribution of aerosols in mine air for LHD #92526: the baseline 

case and Engelhard PTX DOC + muffler case (two measurements each). 

Figure 25 illustrates the effects of B20 and B50 biodiesel blends on the size distribution 

of aerosols in the mine air. The results indicate that the size distributions of the particles 

for these particular biodiesel blends were characterized with somewhat lower GMDs and 

higher peak concentrations than the size distributions observed during the tests with 

#1 diesel (see Table 10 and Figure 25). The average geometric means for B50 (GMD = 

61.76 nm) and B20 (GMD = 65.92 nm) indicate that increasing the biodiesel fraction of a 

blend might result in decreasing the GMDs for the size distributions. In addition, 

a significant increase in the number of particles was found when biodiesel blends were 

used (see Table 4). These results do not indicate a potential trend in the relationship 

between the biodiesel fraction in a blend and total number of particles emitted. 
54

0.00E+00

5.00E+06

1.00E+07

1.50E+07

2.00E+07

2.50E+07

10 100 1000

D_p [nm]

dN/(d log D_p) [#/cm^3]

Baseline + PTX, #1 Baseline + PTX, #2 Biodiesel B20 + PTX, #1

Biodiesel B20 + PTX, #2 Biodiesel B50 + PTX, #1 Biodiesel B50 + PTX, #2

 Figure 25.—Size distribution of aerosols in mine air for LHD #92526 equipped 

with Engelhard PTX DOC and muffler: #2 diesel, biodiesel B20, and biodiesel B50 

(two measurements each). 

The effect of diesel fuel formulation (#1 vs. #2 diesel) on the size distribution of aerosols 

is shown in Figure 26. The size distributions of the particles that were observed during 

the tests with #2 diesel showed, on average, higher GMDs (81.93 vs. 75.42 nm) 

and higher peak number concentrations (1.71 × 107

 vs. 1.63 × 107 #/cm3) than the size 

distributions observed for the tests with #1 diesel (see Table 10 and Figure 26). An 

approximately 5% increase in the number of the particles was found when #2 diesel was 

used instead of #1 (see Table 10). This finding is corroborated by the TEOM results, 

which also showed more than a 20% increase in the TPM concentration when #2 instead 

of #1 diesel was used. 
55

0.00E+00

5.00E+06

1.00E+07

1.50E+07

2.00E+07

2.50E+07

3.00E+07

3.50E+07

10 100 1000

D_p [nm]

dN/(d log D_p) [#/cm^3]

#1 diesel, #1 #1 diesel, #2 #1 diesel, #3

#2 diesel, #1 #2 diesel, #2 #2 diesel, #3

 Figure 26.—Size distribution of aerosols in mine air for LHD #99942 equipped with 

muffler: #1 diesel and #2 diesel (three measurements each). 

Effects of Control Technologies on Ambient Concentrations of 

CO, CO2, NO, and NO2

The average and maximum normalized concentrations of CO, CO2, NO, and NO2

measured at the downstream sampling station are shown in Table 11. The concentrations 

of CO2 were measured using an Innova 1312, and concentrations of CO, NO, and NO2 

were measured using iTX multigas monitors. The obtained concentrations were 

normalized with respect to the MSHA VR specific to the test engine used. The observed 

background concentrations of CO, NO, and NO2 at the upstream sampling station were 

negligible and therefore not used to correct the downstream concentrations. The CO2 

concentrations shown in Table 11 include the background CO2 concentrations, which 

averaged 402 ppm. This was done to facilitate the comparison of the measured CO2

values with the 1973 ACGIH time-weighted average (TWA) threshold limit values 

(TLVs) adopted by MSHA for underground metal/nonmetal mining regulations (30 CFR 

57.5001). 

It is important to note that the peak gaseous concentrations were recorded while the 

vehicle was performing the part of the duty cycle inside and in front of the stope at the 

downstream load/dump point. 
56

Table 11.—Concentrations of CO, CO2, NO, and NO2 at the downstream sampling station 

normalized to the MSHA ventilation rate for the test engine used 

CO, ppm CO2, ppm NO, ppm NO2, ppm Test Type 

Max. Avg. Max. Avg. Max. Avg. Max. Avg. 

#92128 Haul Truck, MSHA VR = 5.66 m3/s (12,000 ft3/min) 

Baseline 11.1 6.7 3,834 2,906 22 16.9 1.1 0.6 

Engelhard DPX 0.0 0.0 3,793 2,716 19 12.5 3.2 2.1 

#92133 Haul Truck,1 MSHA VR = 5.66 m3/s (12,000 ft3/min) 

Baseline + CDT 3.3 2.6 1,763 1,634 7.4 6.0 0.4 0.2 

CleanAIR + CDT 0.0 0.0 1,889 1,736 7.4 6.6 1.0 0.7 

#92506 LHD, MSHA VR = 5.43 m3/s (11,500 ft3/min) 

Baseline 1 18.5 2.3 6,268 2,096 27.7 5.0 0.9 0.0 

Baseline 2 18.4 2.4 5,874 2,054 27.7 5.1 0.9 0.0 

#92526 LHD, MSHA VR = 4.72 m3/s (10,000 ft3/min) 

Baseline 17.5 6.4 7,820 3,691 40.8 17.0 2.6 0.9 

Baseline + PTX 0.0 0.0 7,622 3,917 41.3 19.1 2.9 1.1 

Biodiesel B20 + PTX 0.0 0.0 7,450 3,816 40.1 19.3 2.9 1.1 

Biodiesel B50 + PTX 0.0 0.0 7,622 3,869 44.2 21.1 3.5 1.3 

#99942 LHD, MSHA VR = 7.08 m3/s (15,000 ft3/min) 

Baseline, #1 diesel 24.2 4.2 8,740 2,941 48.5 13.5 3.1 0.5 

Baseline, #2 diesel 23.4 4.4 9,028 2,948 50.2 13.5 2.7 0.5 

DCL MINE–X 0.0 0.0 8,789 2,884 43.3 11.1 5.7 1.5 

1

Since tests involving vehicle #92133 were conducted while VRs were below MSHA VR for the engine, the absolute 

values of the data for this vehicle are questionable. For example, CO2 is low compared to CO2 for other vehicles; 

however, the values can be used to assess relative effect of control technologies. 

Carbon Monoxide (CO) 

The average and maximum VR-normalized concentrations of CO, shown in Table 11, are 

significantly below the TWA TLV of 50 ppm for CO. The concentrations of CO were 

found to be practically undetectable for tests when the catalyzed DPF systems from 

Engelhard and DCL and the DOC from Engelhard (see Table 11) were fitted to the test 

vehicles. Even in the tests when the engines were fitted with mufflers, the concentrations 

of CO were relatively low. The CO concentrations observed in the isolated zone are in 

the limits of concentrations estimated on the basis of the tailpipe emissions 

measurements. 
57

Carbon Dioxide (CO2) 

The traces of VR-normalized concentrations of CO2 observed for the tests conducted 

during the study are shown in Figures 27–29. The averages and maximums are also 

presented in Table 11. Both average and maximum CO2 concentrations at the 

downstream station were below the TWA TLV level of 5,000 ppm for CO2 during the 

tests with haul truck #92128. For the tests involving the other tested vehicles, the 

average normalized concentrations of CO2 were found to be under the TWA TLV for 

CO2, but the peak concentrations were found to be significantly over the TWA TLV 

(see Table 11 and Figures 27–29). 

The concentrations of CO2 were found to be unaffected by the tested DPF systems from 

Engelhard and DCL and the Engelhard PTX DOC (see Table 11). The concentrations 

observed in the isolated zone are in the limits of concentrations estimated on the basis of 

the tailpipe emissions measurements. 

0.0

1000.0

2000.0

3000.0

4000.0

5000.0

6000.0

7000.0

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

Time [s]

Concentrations [ppm]

Baseline, #1 diesel Baseline, #2 diesel

Figure 27.—Normalized CO2 concentrations for the tests with LHD #92506. 
58

 

0.0

1000.0

2000.0

3000.0

4000.0

5000.0

6000.0

7000.0

8000.0

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

Time [s]

Concentrations [ppm]

Baseline Baseline + PTX Biodiesel B20 + PTX Biodiesel B50 + PTX

Figure 28.—Normalized CO2 concentrations for the tests with LHD #92526. 

 

0.0

1000.0

2000.0

3000.0

4000.0

5000.0

6000.0

7000.0

8000.0

9000.0

10000.0

0 1000 2000 3000 4000 5000 6000

Time [s]

Concentrations [ppm]

Baseline, #1 diesel Baseline, #2 diesel DCL MineX

Figure 29.—Normalized CO2 concentrations for the tests with LHD #99942. 
59

Nitric Oxide (NO) 

For all tests, the average normalized concentrations of NO shown in Table 11 were found 

to be lower than the TWA TLV level for NO of 25 ppm. In the case of LHDs #92526 

(see Table 11 and Figure 30) and #99942 (see Table 11 and Figure 31), the peak 

normalized concentrations were found to be significantly above the TWA TLV. 

An analysis of the results shown in Table 11 revealed that the average and peak 

concentrations of NO were slightly lower for the tests when the vehicles were equipped 

with DPF systems rather than with mufflers. The analysis also showed that the biodiesel 

blends slightly increased the concentrations of NO over the baseline established with 

#1 diesel fuel. 

 

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

0 1000 2000 3000 4000 5000 6000

Time [s]

Concentrations [ppm]

Baseline Baseline + PTX Biodiesel B20 + PTX Biodiesel B50 + PTX

Figure 30.—Normalized NO concentrations for the tests with LHD #92526. 
60

 

0.0

10.0

20.0

30.0

40.0

50.0

60.0

0 1000 2000 3000 4000 5000 6000 7000 8000

Time [s]

Concentrations [ppm]

Baseline, #1 diesel Baseline, #2 diesel DCL MineX

Figure 31.—Normalized NO concentrations for the tests with LHD #99942. 

Nitrogen Dioxide (NO2) 

Assessing the effects of the DPF systems, particularly those that were washcoated with a 

platinum catalyst, on concentrations of NO2 in mine air was one of the major objectives 

of this study. The results of the NO2 measurements, summarized in Table 11, show that 

the average normalized concentrations of NO2 increased approximately twofold (1.3 vs. 

0.6 ppm) when haul truck #92128 was equipped with the Engelhard DPX DPF system 

instead of a muffler (see Figure 32). Comparable increases (2.1 vs. 0.9 ppm) in NO2

concentration was observed for the DCL MINE–X DPF system and also for the 

CleanAIR DPF system (0.7 vs. 0.2 ppm) (see Table 11). It is important to note that if the 

required MSHA VRs were maintained during the tests, the average concentration of NO2

over the test periods would not have exceeded 3 ppm, the 1973 ACGIH TWA TLV limit 

for NO2. It is also important to note that, on several occasions while #99942 equipped 

with DCL MINE–X was operated within and in front of the downstream stope, the 

VR-normalized peak concentrations exceeded 5 ppm, the 1973 ACGIH short-term 

exposure limit (STEL) for NO2 currently used by MSHA as a ceiling limit to regulate 

exposure of underground metal and nonmetal miners to NO2 (30 CFR 57.5001) (see 

Figure 33). An analysis of the data showed that the average and peak concentrations of 

NO2 were only slightly higher in the tests when LHD #92526 was fueled with biodiesel 

blends instead of regular diesel fuel. The results of the test when LHD #92526 was fitted 

with the Engelhard PTX DOC and a muffler showed insignificantly higher NO2 

emissions than when only the muffler was fitted to the vehicle. 
61

 

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 2000 4000 6000 8000 10000 12000

Time [s]

Concentrations [ppm]

Baseline Engelhard DPX

 Figure 32.—Normalized NO2 concentrations at the downstream sampling station for the 

tests with haul truck #92128. 

0.0

1.0

2.0

3.0

4.0

5.0

6.0

0 1000 2000 3000 4000 5000 6000 7000 8000

Time [s]

Concentrations [ppm]

Baseline, #1 diesel Baseline, #2 diesel DCL MineX

 Figure 33.—Normalized NO2 concentrations at the downstream sampling station for the 

tests with LHD #99942. 
62

It is important to note that the discussion presented in this section is based on the 

measurements obtained at the downstream sampling station. The area samples collected 

at this station were primarily used to evaluate the performance of the tested control 

technologies. However, concentrations of CO, NO, and NO2 were also measured with an 

iTX multigas monitor located on the test vehicles. Since the vehicle sampling locations 

were relatively close to the operators, the results can be used to estimate the exposure of 

the operators to the gases. The concentrations of the measured gases at the downstream 

and vehicle locations were found to be comparable and, in most cases, slightly higher 

peaks were observed on the vehicle (see Figure 34). The higher concentrations indicate 

that the operators might have been exposed to concentrations that are somewhat higher 

than those shown in Table 11. 

 

0.0

1.0

2.0

3.0

4.0

5.0

6.0

0 1000 2000 3000 4000 5000 6000 7000 8000

Time [s]

Concentrations [ppm]

Baseline #1 diesel, downstream Baseline #1 diesel, vehicle

DCL MineX, downstream DCL MineX, vehicle

 Figure 34.—Normalized NO2 concentrations at the downstream and vehicle sampling stations 

for the baseline (#1 diesel) and DCL MINE–X DPF system tests with LHD #99942. 
63

Effects of Filtration Systems on Exhaust Temperature and 

Engine Back Pressure 

The exhaust gas temperature and engine back pressure were recorded every 10 s on the 

vehicles used to test the filtration systems. The critical temperature spreadsheet available 

in the NIOSH-MSHA DPF selection guide [MSHA 2004] was used to analyze the 

exhaust temperature traces and to calculate T30, the temperature exceeded 30% of the 

time, for several runs. The temperatures below 130 °C were assumed to indicate that the 

engine was not running, and they were excluded from considerations. T30 is used by the 

DPF suppliers to select and optimize a DPF system for application. The result of such 

analysis is demonstrated on the example of haul truck #92133 in Figure 35. 

 

0

10

20

30

40

50

60

70

80

90

100

200210220230240250260270280290300310320330340350360370380390400410420430440450460470480490500550

Temperature [°C]

Cumulative Frequency [%]

0

20

40

60

80

100

120

140

160

180

200

Frequency

Frequency Cumulative Frequency

 Figure 35.—Temperature frequency distribution and cumulative frequency distribution 

used to determine T30 for haul truck #92133 during CleanAIR DPF system test. 

The engine back pressure traces were closely examined for the instances when back 

pressure was decreasing during the test runs. It was assumed that during those instances 

the exhaust temperature was sufficient to burn off part of the collected DPM. The back 

pressures are reported as ranges at the start and at the end of the test runs because they are 

exhaust flow-dependent, and those flows vary with engine speed and load over the duty 

cycle. 

Table 12 shows the results of the analysis performed on the data collected on the exhaust 

temperatures and engine back pressures. In several instances, data were not collected due 

to instrument failure. 
64

Table 12.—Results of analysis of exhaust temperatures and engine back pressures 

Back Pressure 

Ranges, 

kPa (in H2O) 

Test Type T30 Temperature, °C 

Start of test: 

min-max 

End of test: 

min-max 

Did DPF 

regenerate 

over duty 

cycle? 

#92128 Haul Truck 

Baseline 260 0.5–3.7 (2–15) — 

Engelhard DPX 265 8.7–25 (35–100) 8.7–25 (35–100) No 

#92133 Haul Truck 

Baseline + CDT 410 N/A 

CleanAIR + CDT 440 4.0–15.4 (16–62) 0.62–2.2 (2.5–9) Yes 

#92506 LHD 

Baseline 1 455 N/A 

Baseline 2 455 N/A 

DCL BlueSky 490 3.0–7.0 (12–28) 8.7–20 (35–80) No 

Donaldson 370 0.07–0.57 (0.25–2.3) 0.07–0.57 (0.25–2.3) 

#92526 LHD 

Baseline 460 0.5–2.7 (2–11) 

Baseline + PTX 440 1.1–2.86 (4.5–11.5) 

ECS Cattrap Faulted 2.5–8.2 (10–33) 2.5–8.2 (10–33) No 

Biodiesel B20+PTX 440 1.5–2.86 (6–11.5) 

Biodiesel B50+PTX Faulted 1.2–2.86 (5–11.5) 

#99942 LHD 

Baseline, #1 diesel Faulted Faulted 

Baseline, #2 diesel 500 3.0–6.2 (12–25) 

DCL MINE–X Faulted Faulted Faulted Unknown 

DPF Regeneration 

An example of exhaust temperature and engine back pressure traces recorded during this 

study is shown in Figure 36. The data presented in this figure indicate that the CleanAIR 

DPF system, which was used with a CDT fuel additive, had been regenerating during the 

test cycle. Similar measurements performed on the other tested vehicles indicate that the 

Engelhard, DCL BlueSky, and ECS DPF systems did not regenerate during the test runs. 

In addition, there is no indication that the relatively clean Donaldson high-temperature 

DFE was regenerating during the short duration of the test. There are not enough data to 

verify whether the DCL MINE–X DPF system regenerated over the test cycle. 
65

 

Exhaust Temperature 

[°C]

Back Pressure [kPa]

0

100

200

300

400

500

600

8:38:24 9:50:24 11:02:24 12:14:24 13:26:24 14:38:24

Local Time [hh:mm:ss]

Exhaust Temperature [°C]

0

2

4

6

8

10

12

14

16

18

Back Pressure [kPa]

 Figure 36.—Exhaust temperature and engine back pressure trace recorded during the 

isolated zone test of the CleanAIR DPF system. 

Exhaust Temperature 

The exhaust temperatures were found to be affected by the type of tested vehicle/engine 

and by the configuration of the exhaust system. In the case of haul truck #92128 and 

LHDs #92506, #92526, #99942, temperatures were relatively high (see Table 12), with 

T30 temperatures higher than 400 °C. In contrast, the temperatures were relatively low 

for the two tests with haul truck #92128; the T30 temperatures were around 260 °C. 

These temperatures are surprisingly low when one takes in consideration that haul trucks 

#92128 and #92133 are similar in design and powered by similar engines. 

The measurements on haul truck #92133 showed that T30 increased by 30 °C when the 

muffler was replaced with the CleanAIR DPF system. A similar increase in T30 (35 °C) 

was observed when the muffler on #92506 was replaced by the DCL BlueSky DPF 

system. The increase in exhaust temperature corresponds to an observed increase in 

engine back pressure, which typically occurs when the muffler is replaced with a DPF 

system. 

T30 for the Donaldson DFE was found to be lower than T30 for the muffler (370 vs. 

455 °C). It is important to note that the exhaust temperatures at the inlet filter face of the 

DFE often exceeded 260 °C (500 °F), the maximum temperature recommended by the 

manufacturer. 
66

Engine Back Pressure 

With the CleanAIR DPF system installed, the peak engine back pressure varied from 4.0 

to 15.4 kPa (16 to 62 in H2O) at the start of the test and decreased to 0.62–2.2 kPa 

(2.5–9 in H2O) at the end of the 3-hr 22-min test (see Figure 36). The engine back 

pressures with the Engelhard DPX and DCL BlueSky DPF systems were excessive, with 

peaks ranging from 8.7 to 25 kPa (35 to 100 in H2O) and from 8.7 to 20 kPa (35 to 

80 in H2O), respectively. The peak values caused by the high load parts of the duty cycle 

did not decrease over the test runs, indicating that DPF regeneration did not occur during 

those test runs. On the contrary, in the case of the Donaldson DFE, the engine back 

pressure remained low throughout the test, ranging from 0.07 to 0.57 kPa (0.25 to 2.3 in 

H2O) over the course of the test. 

RESULTS OF TAILPIPE EMISSIONS MEASUREMENTS 

This section presents and discusses the results of particulate matter and gaseous 

emissions measurements. Particulate samples were collected at high-idle (HI) and torque 

converter stall (TCS) modes. Gaseous emissions were measured at HI, TCS, and lowidle (LI) modes. All but three of the control technologies tested involve DPFs. The 

results of the measurements are presented below. 

Particulate Matter Emissions: EC 

The EC results from the exhaust pipe measurements for the tested control technologies 

are summarized in Table 13. The reduction in EC was calculated by comparing the 

measurement taken upstream (untreated or raw exhaust) to that taken downstream of the 

DPF or DOC. For biodiesel tests, reductions were computed by comparing engine-out 

emissions upstream of the Engelhard PTX DOC for the baseline fuel and for the biodiesel 

blends. The EC reductions, obtained by comparing measurements taken downstream of 

the DOC, are somewhat lower. 
67

Table 13.—Effects of control technologies on elemental carbon emissions 

EC, μg/m3

HI 

EC, μg/m3 

TCS 

Reduction of EC, 

% Test Type 

Upstream Downstream Upstream Downstream HI TCS 

#92128 Haul Truck 

Engelhard DPX 2,369 <920 18,230 <920 >61 >95

#92133 Haul Truck 

CleanAIR 6,043 <920 33,537 <920 >85 >97

#92506 LHD 

DCL BlueSky 5,282 1,055 23,316 <920 80 >96

Donaldson 3,353 <920 18,230 1,748 >72 90

#92526 LHD 

ECS Cattrap 8,898 <920 8,254 <920 >90 >89

Baseline + PTX 16,049 11,529 8,230 6,712 28 18

Biodiesel B20 + PTX 13,798 12,532 5,641 4,858 14 31

Biodiesel B50 + PTX 9,890 8,690 4,537 4,217 38 45

#99942 LHD 

DCL MINE–X 40,838 <920 16,417 <920 >98 >94

For all but two instances, the EC found on the sample collected downstream of the DPFs 

was below the limit of detection of NIOSH Analytical Method 5040. For these samples, 

the limit of quantification (LOQ) of the method was used as the sample EC value. The 

method has an LOQ of approximately 1.5 μg per filter for EC and is about three times the 

nominal limit of detection. The LOQ, which is greater than the actual EC on the sample, 

was converted into an equivalent EC concentration (920 μg/m3

) for the exhaust volume 

sampled and was used to compute the EC reduction efficiency of the DPF. This 

procedure results in an estimate of the control efficiency, which becomes increasingly 

conservative as the upstream EC concentrations become less than a factor of 10 greater 

than the LOQ equivalent concentration. For all but one (the DCL MINE–X) of the DPFs 

tested at HI, the upstream EC was so low that the necessary use of the LOQ-equivalent 

EC concentration for the downstream measurement resulted in an underestimation of the 

EC reduction for that DPF (see Table 13). 

Most of the upstream EC concentrations at TCS were high enough relative to the LOQ 

equivalent used for the downstream samples to allow an estimation of the EC reduction 

efficiencies of the DPFs tested. At TCS, the emissions measurements showed that the 

tested DPF systems were over 90% efficient in removal of EC (see Table 13 and 

Figure 37). Figure 37 shows the reduction of EC emissions obtained for all of the control 

technologies tested with the engine at TCS. The darker bars in the figure represent the 

EC reductions calculated when EC could be quantified, while the lighter bars show the 

minimum EC reductions estimated using the LOQ. 
68

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

100.00

Biodiesel

B20 + PTX

Biodiesel

B50 + PTX

Donaldson ECS Cattrap DCL MineX Engelhard

DPX

DCL

BlueSky

CleanAir

Type of Control Technology

Reduction in EC [%]

Figure 37.—Reduction of EC emissions at TCS. 

An examination of the EC results for LHD #92526 in Table 13 shows that in every 

emissions test with the DOC, the EC concentration downstream of the DOC was lower 

than the upstream concentration, a finding consistent with the EC reduction results 

obtained for the same DOC in the isolated zone. 

Particulate Matter Emissions: Bacharach Smoke Number 

In this study, the Bacharach smoke number was used to provide a qualitative estimate of 

the effectiveness of a DPF to reduce DPM and to avoid testing a defective DPF. The 

smoke numbers that were obtained upstream and downstream of the DPFs or DOC are 

presented in Table 14. No smoke number data were gathered for LHD #92506 because 

of a scheduling constraint. For the DPFs measured, the upstream smoke number ranged 

from 3 to 9, while all of the downstream smoke numbers measured zero. Values for the 

smoke number of untreated exhaust can range anywhere from 3 to 9 (totally black). This 

study showed that the smoke number method can be used to track the filtering ability of a 

DPF during use and untreated engine emissions if they are less than 9. 
69

Table 14.—Effects of control technologies on DPM emissions: Bacharach smoke number 

Bacharach smoke number 

HI 

Bacharach smoke number 

Test Type TCS 

Upstream Downstream Upstream Downstream 

#92128 Haul Truck 

Engelhard DPX 3.0 0.0 7.0 0.0 

#92133 Haul Truck 

CleanAIR 3.0 0.0 4.0 0.0 

#92526 LHD 

Biodiesel B20 + PTX 8.0 8.0 7.5 6.0 

Biodiesel B50 + PTX 7.5 7.5 7.5 6.0 

#99942 LHD 

DCL MINE–X 9.0 0.0 8.0 0.0 

The smoke numbers for the tested DPF systems from Engelhard, CleanAIR, and DCL 

(MINE–X) confirm that these systems were quite effective in reducing DPM emissions. 

A comparison of the smoke numbers obtained upstream and downstream of the tested 

Engelhard PTX DOC indicated a reduction in DPM. 

The smoke numbers presented in Table 14 do not show significant reductions of DPM 

concentrations in the exhaust for the biodiesel blends. A comparison of the B20 and B50 

smoke numbers obtained under the same engine test mode or sampling location shows 

little or no difference between the two blends. This finding is contrary to the relatively 

large difference in isolated zone and tailpipe EC concentrations for these two blends. 

Additionally, the DOC, which had a discernable effect on smoke number, showed only a 

small difference in tailpipe or EC concentration in the isolated zone test. Thus, the 

smoke number can be considered only as a rough estimate of DPM emissions and is most 

useful for tracking relative changes in DPM emissions from an engine or out of a DPF 

system. 

Emissions of CO, CO2, NO, and NO2

The effects of the tested control technologies on tailpipe emissions of CO, CO2, NO, and 

NO2 were estimated from the measurements made upstream and downstream of the tested 

control technologies. The gases were measured for three engine operating conditions—

LI, HI, and TCS—using ECOM KL (NIOSH) and Enerac 400 (SMC) combustion 

analyzers. 

The effects of the biodiesel blends on gaseous emissions were obtained by comparing the 

results of emissions measurements obtained upstream of the Engelhard PTX DOC on the 

LHD #92526 fueled with the biodiesel blend to the results upstream of the ECS Cattrap 

when the LHD was fueled with #1 diesel fuel. The effects of the Engelhard PTX DOC 

on the gaseous emissions were evaluated by comparing the upstream to the downstream 

measurements conducted during the tests on the LHD fueled with biodiesel blends. 
70

The agreement between the ECOM KL and Enerac 400 was found to be within 

experimental error in most instances. Some discrepancies in the readings can be 

explained by differences in the protocols used by the instruments; in other instances, the 

discrepancies have no explanation. This is certainly the case for the NO measurements 

performed downstream of the Engelhard DPF on truck #92128 at LI. 

The results of the CO concentration measurements are shown in Table 15. The DPF 

systems and DOC tested in this study drastically reduced the concentrations of CO. The 

reductions can be attributed to the platinum catalyst used in each of the systems. The 

Donaldson disposable filter also (surprisingly) reduced CO emissions. The extremely 

high concentrations of CO in the exhaust of LHD #92506 at HI conditions indicate 

serious problems with the engine fueling system. The CO emissions from the other 

vehicles were within the manufacturer’s specifications. 

Table 15.—CO tailpipe emissions 

CO, ppm 

HI 

CO, ppm 

LI 

CO, ppm 

TCS Test Type Upstream 

Downstream Upstream Downstream Upstream Downstream 

Instrument 

#92128 Haul Truck 

Engelhard DPX 217.0 0.0 197.0 0.0 136.0 0.0 ECOM 

204.0 0.0 170.0 0.0 131.0 0.0 Enerac 

#92133 Haul Truck 

CleanAIR Systems 314.0 2.0 100.0 0.0 114.0 0.0 ECOM 

301.0 0.0 110.0 0.0 109.0 11.0 Enerac 

#92506 LHD 

DCL BlueSky 2,437.0 1,329.0 168.0 3.0 386.0 3.0 ECOM 

2,207.0 910.0 208.0 0.0 460.0 0.0 Enerac 

Donaldson N/A N/A N/A N/A N/A N/A ECOM 

2,960.0 1,359.0 248.0 79.0 268.0 210.0 Enerac 

#92526 LHD 

ECS Cattrap 278.0 2.0 N/A N/A 106.0 0.7 ECOM 

238.0 0.0 168.0 0.0 98.0 0.0 Enerac 

Biodiesel B20 + 18.7 17.5 158.0 1.0 70.7 1.0 ECOM 

PTX 167.0 16.0 173.0 0.0 74.0 4.0 Enerac 

Biodiesel B50 + 203.0 22.0 N/A N/A 75.0 6.0 ECOM 

PTX 174.0 21.0 159.0 0.0 76.0 13.0 Enerac 

#99942 LHD 

DCL MINE–X 375.7 0.0 N/A N/A 228.5 0.0 ECOM 

343.0 0.0 125.0 0.0 215.0 0.0 Enerac 

The instrument-calculated concentrations of CO2 in the exhaust of the tested vehicles/

configurations are shown in Table 16. The CO2 emissions were not significantly affected 

by any of the control technologies. 
71

Table 16.—CO2 tailpipe emissions 

CO2, % 

HI 

CO2, % 

LI 

CO2, % 

TCS Test Type Upstream 

Downstream Upstream Downstream Upstream Downstream 

Instrument 

#92128 Haul Truck 

Engelhard DPX 4.9 4.9 2.9 0.4 8.6 8.0 ECOM 

4.5 4.5 2.5 2.5 8.2 8.2 Enerac 

#92133 Haul Truck 

CleanAIR Systems 4.2 4.4 2.1 2.3 8.0 8.1 ECOM 

4.5 4.5 2.3 2.3 8.1 8.1 Enerac 

#92506 LHD 

DCL BlueSky N/A N/A N/A N/A N/A N/A ECOM 

6.4 6.4 2.6 2.6 10.5 10.5 Enerac 

Donaldson N/A N/A N/A N/A N/A N/A ECOM 

5.1 5.1 1.1 1.1 8.3 8.3 Enerac 

#92526 LHD 

ECS Cattrap 5.5 5.6 N/A N/A 7.5 7.5 ECOM 

5.2 5.2 2.4 2.4 7.0 7.0 Enerac 

Biodiesel B20 + 4.8 4.8 2.5 2.4 6.8 7.0 ECOM 

PTX 4.7 4.7 2.1 2.1 6.6 6.6 Enerac 

Biodiesel B50 + 4.6 4.7 N/A N/A 6.7 7.0 ECOM 

PTX 5.3 5.3 2.7 2.7 5.3 5.3 Enerac 

#99942 LHD 

DCL MINE–X 5.4 5.3 N/A N/A 9.3 9.3 ECOM 

5.4 5.4 2.5 2.5 9.1 9.1 Enerac 

The results of the NO emissions measurements are summarized in Table 17. All tested 

systems beside the CleanAIR Systems DPF system significantly affected NO emissions. 

NO emissions were significantly lower for the Engelhard, ECS, and DCL (MINE–X) 

DPF systems for all engine modes. The effects on NO emissions from the DCL BlueSky 

and the Donaldson filtration systems were found to be strongly dependent on the engine 

mode. The effects of biodiesel blends on NO emissions could be characterized as 

marginal. 
72

Table 17.—NO tailpipe emissions 

NO, ppm 

HI 

NO, ppm 

LI 

NO, ppm 

TCS Test Type Upstream 

Downstream Upstream Downstream Upstream Downstream 

Instrument 

#92128 Haul Truck 

Engelhard DPX 439.5 360.0 414.0 3.0 500.0 341.0 ECOM 

434.0 389.0 412.0 292.0 506.0 427.0 Enerac 

#92133 Haul Truck 

CleanAIR Systems 240.0 281.0 176.0 161.0 407.0 374.0 ECOM 

260.0 283.0 188.0 188.0 435.0 415.0 Enerac 

#92506 LHD 

DCL BlueSky 124.0 203.0 284.0 278.0 476.0 355.0 ECOM 

172.0 214.0 300.0 303.0 491.0 443.0 Enerac 

Donaldson 213.0 N/A N/A N/A 423.5 N/A ECOM 

163.0 287.0 373.0 151.0 529.0 474.0 Enerac 

#92526 LHD 

ECS Cattrap 186.5 143.0 245.0 N/A 427.0 301.7 ECOM 

204.0 146.0 240.0 85.0 452.0 259.0 Enerac 

Biodiesel B20 + PTX 189.3 192.0 240.0 215.0 491.7 483.0 ECOM 

209.0 208.0 211.0 213.0 492.0 492.0 Enerac 

Biodiesel B50 + PTX 161.0 159.0 225.0 N/A 449.0 426.0 ECOM 

205.0 196.0 226.0 176.0 487.0 440.0 Enerac 

#99942 LHD 

DCL MINE–X 206.0 150.5 N/A N/A 547.0 438.5 ECOM 

250.0 159.0 329.0 113.0 607.0 523.0 Enerac 

The results of the NO2 emission measurements are summarized in Table 18. 

Significantly higher NO2 concentrations were observed downstream than upstream of the 

platinum-catalyzed DPFs tested in this study (Engelhard DPX and DCL MINE–X). 

Fourfold increases in NO2 emissions were observed at TCS conditions. Significant 

increases in NO2 emissions were also observed for the ECS Cattrap system, which by 

itself should not have an effect on NO2 emissions owing to using a base-metal catalyst. 

However, a new platinum-catalyzed ECS DOC had been installed after the DPF. Thus, 

that system, probably because of the DOC, increased NO2 emissions almost sixfold at 

TCS conditions. The results of the measurements show no significant increase in NO2

emissions for the biodiesel blends relative to the #1 diesel baseline. 
73

Table 18.—NO2 tailpipe emissions 

NO2, ppm 

HI 

NO2, ppm 

LI 

NO2, ppm 

TCS 

Test Type Upstream 

Downstream Upstream Downstream Upstream Downstream 

Instrument 

#92128 Haul Truck 

Engelhard DPX 58.0 98.0 73.0 3.0 25.0 89.0 ECOM 

87.0 121.0 72.0 170.0 23.0 101.0 Enerac 

#92133 Haul Truck 

CleanAIR Systems 51.0 12.0 21.0 43.0 25.0 39.0 ECOM 

51.0 8.0 10.0 38.0 11.0 7.0 Enerac 

#92506 LHD 

DCL BlueSky 83.0 6.0 40.0 50.0 16.0 16.0 ECOM 

48.0 0.0 51.0 65.0 2.0 14.0 Enerac 

Donaldson — — — — — — ECOM 

28.0 1.0 61.0 0.0 0.0 1.0 Enerac 

#92526 LHD 

ECS Cattrap 34.0 59.0 55.0 — 17.0 121.0 ECOM 

31.0 81.0 68.0 177.0 31.0 163.0 Enerac 

Biodiesel B20 + 22.0 16.0 34.0 36.0 16.0 36.0 ECOM 

PTX 215.0 213.0 257.0 251.0 501.0 509.0 Enerac 

Biodiesel B50 + 21.0 21.0 18.0 — 12.0 40.0 ECOM 

PTX 6.0 3.0 43.0 41.0 6.0 8.0 Enerac 

#99942 LHD 

DCL MINE–X 28.3 68.0 — — 17.5 89.5 ECOM 

10.0 85.0 29.0 190.0 10.0 45.0 Enerac 

These results show that NO2 concentrations need to be closely monitored in underground 

work areas where vehicles equipped with aftertreatment components that have a high 

potential of converting NO to NO2 are used. 
74

SUMMARY 

The effects of selected diesel emissions control technologies on the airborne concentrations of particulate matter and selected gases were assessed using results of tests conducted in an isolated zone in an underground metal mine. Although six DPF systems 

were tested, results for only two of the systems were not compromised by ventilation 

problems: the Engelhard DPX and the DCL MINE–X. However, ventilation rates for the 

baseline test and the test of the CleanAIR DPF system on truck #92133 were equal, 

allowing a comparison to be made. The results of the tests conducted with LHD #92526 

were used to quantify the effects of the biodiesel blends B20 and B50 and an Engelhard 

model PTX DOC. 

The Engelhard DPX, DCL MINE–X, and CleanAIR DPF systems reduced mass concentrations of EC by approximately 96%, 88%, and 99%, respectively. However, the Engelhard PTX DOC did not exhibit quantifiable effects on concentrations of EC. The 

analysis showed reductions in EC concentrations of 26% and 48% for B20 and B50 

yellow grease biodiesel blends, respectively. Only a minor difference in the effects of 

#1 diesel and #2 diesel on EC concentrations was found. 

The analysis also showed that the Engelhard DPX and DCL MINE–X DPF systems 

reduced TPM concentrations in mine air by approximately 75%. These reductions were 

lower than those observed for EC. A similar statement can be made for the B20 and B50 

biodiesel blends, which reduced TPM concentrations by 9% and 24%, respectively. 

However, the differences in the EC and TPM reductions can be attributed to the fact that 

those aerosols that are transparent to the EC analysis can contribute significantly to the 

TPM measured by the TEOM. The TPM concentrations were 21% higher when #2 diesel 

was used in place of #1 diesel. 

The results of size-selective measurements qualitatively agree with the EC and TPM 

results. The measurements showed dramatic reductions in the number of larger particles 

when the Engelhard DPX and DCL MINE–X DPF systems were used instead of a 

muffler. The size distributions of the particles that are observed for the DPF tests are 

characterized with substantially lower GMDs and higher peak number concentrations 

than the size distributions observed for the baseline tests. A significant increase in the 

total number of particles, approximately 60%–80%, was evident for both cases where 

mufflers were replaced with DPF systems. The size distributions of the particles that 

were observed for the tests with the Engelhard PTX DOC are characterized with 

somewhat lower GMDs (72.40 vs. 85.74 nm) and higher peak number concentrations 

(1.01 × 107

 vs. 8.56 × 106 #/cm3) than the size distributions observed during tests with the 

muffler alone. An approximately 18% increase in the number of particles was found 

when the muffler was replaced with a DOC and muffler combination. 

The results of the tests with B20 and B50 biodiesel blends indicate that the size 

distributions of the particles for those particular biodiesel blends were characterized with 

somewhat lower GMDs and higher peak concentrations than the size distributions 

observed during the tests with #1 diesel. The average geometric means for B50 
75

(GMD = 61.76 nm) and B20 (GMD = 65.92 nm) indicated that increasing the biodiesel 

fraction of a blend might result in smaller GMDs for the aerosol size distributions. In 

addition, a significant increase in the number of particles was found when the B20 and 

B50 biodiesel blends were used (20.4% and 14.1%, respectively). 

The size distributions of the particles that were observed during the tests with #2 diesel 

showed, on average, higher GMDs (81.93 vs. 75.42 nm) and higher peak number 

concentrations (1.71 × 107

 vs. 1.63 × 107 #/cm3) than the size distributions observed for 

the tests with #1 diesel. An approximately 5% increase in the number of particles was 

found when #2 instead of #1 diesel was used. 

Catalyzed DPF systems (Engelhard DPX and DCL MINE–X) and the Engelhard PTX 

DOC rendered the concentrations of CO practically undetectable. It should be noted that 

the concentrations of CO were relatively low even during the tests when the engines were 

fitted with mufflers. The concentrations of CO2 were found to be unaffected by the tested 

DPF systems from Engelhard and DCL and the Engelhard PTX DOC. An analysis of the 

results also revealed that the average and peak concentrations of NO were slightly lower 

for the tests when the vehicles were equipped with DPF systems rather than mufflers. In 

addition, the analysis showed that the biodiesel blends slightly increased the 

concentrations of NO over the baseline established with #1 diesel fuel. Assessing the 

effects of the DPF systems, particularly those that were washcoated with a platinum 

catalyst, on concentrations of NO2 in mine air was one of the major objectives of this 

study. The results of the NO2 measurements showed that the average normalized 

concentrations of NO2 increased approximately twofold (1.3 vs. 0.6 ppm) when the 

muffler was replaced with the Engelhard DPX DPF system. Comparable increases (2.1 

vs. 0.9 ppm) in NO2 concentration were observed for the DCL MINE–X DPF system and 

the CleanAIR DPF system (0.7 vs. 0.2 ppm). An analysis of the data showed that the 

average and peak concentrations of NO2 were only slightly higher in the tests when LHD 

#92526 was fueled with biodiesel blends instead of regular diesel fuel. The results also 

showed that use of the Engelhard PTX DOC resulted in an insignificant increase in NO2

concentrations. 

The exhaust temperature and engine back pressure measurements showed that the 

CleanAIR DPF system, which uses a CDT fuel-borne catalyst, had been regenerating 

during the test cycle. Similar measurements indicate that the Engelhard DPX, DCL 

BlueSky, and ECS Cattrap DPF systems did not regenerate during the test runs. In 

addition, there was no indication that the relatively clean Donaldson high-temperature 

DFE was regenerating during the short duration of the test. There were not enough data 

to verify whether the DCL MINE–X DPF system regenerated over the test cycle. It is 

important to note that the exhaust temperatures at the inlet filter face of the DFE often 

exceeded 260 °C (500 °F), the maximum temperature recommended by the manufacturer. 

The engine back pressure was a concern only for the Engelhard DPX and DCL BlueSky 

DPF systems. For these two systems, peak back pressures ranged from 8.7 to 25.0 kPa 

(35 to 100 in H2O) and from 8.7 to 20 kPa (35 to 80 in H2O), respectively. In the case of 
76

the Donaldson DFE, the engine back pressure remained low throughout the test, ranging 

from 0.07 to 0.57 kPa (0.25 to 2.3 in H2O) over the course of the test. 

In general, the results of tailpipe emissions tests were found to be in good agreement with 

findings from the isolated zone tests. The study showed that limited tailpipe emissions 

measurements similar to those used in this study can be used by mine operators to 

identify potential issues related to engine-out emissions and implementation of various 

control strategies and technologies. 

In addition, this short-term study revealed several other important technical issues 

affecting implementation and operation of DPF systems in underground mines. 

Regeneration, reliability, and durability of DPF systems in underground operations are 

recognized as the major areas that need to be addressed. 
77

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