The Effectiveness of Selected Technologies in Controlling 

Diesel Emissions in an Underground Mine - 

Isolated Zone Study at Stillwater Mining Company’s Nye Mine 

Final Report to Metal/Nonmetal Diesel Partnership 

January 5, 2004 

Compiled by 

 Aleksandar Bugarski1

, George Schnakenberg2, Jim Noll3, Steve Mischler4, Larry 

Patts5

, Jon Hummer6, Shawn Vanderslice7, Mike Crum8 and Rick Anderson9

 

1

 National Institute of Occupational Safety and Health, Pittsburgh Research Laboratory, phone: 

412.386.5912, e-mail: ABugarski@cdc.gov 

2

 National Institute of Occupational Safety and Health, Pittsburgh Research Laboratory, phone: 

412.386.6655, e-mail: GSchnakenberg@cdc.gov 

3

 National Institute of Occupational Safety and Health, Pittsburgh Research Laboratory, phone: 

412.386.6828, e-mail: JNoll@cdc.gov 

4

 National Institute of Occupational Safety and Health, Pittsburgh Research Laboratory, phone: 

412.386.6588, e-mail: SMischler@cdc.gov 

5

 National Institute of Occupational Safety and Health, Pittsburgh Research Laboratory, phone: 

412.386.6852, e-mail: LPatts@cdc.gov 

6

 National Institute of Occupational Safety and Health, Pittsburgh Research Laboratory, phone: 

412.386.4974, e-mail: JHummer@cdc.gov 

7

 National Institute of Occupational Safety and Health, Pittsburgh Research Laboratory, phone: 

412.386.6756, e-mail: SVanderslice@cdc.gov 

8

 Stillwater Mining, phone: (406) 328-8501, e-mail: MCrum@stillwatermining.com 9

 Stillwater Mining, phone: (406) 328-8616, e-mail: RAnderson@stillwatermining.com 
1

Table of Contents 

Table of Contents................................................................................................................ 1 

Table of Figures .................................................................................................................. 2 

Table of Tables ................................................................................................................... 4 

Introduction......................................................................................................................... 5 

Objectives ........................................................................................................................... 6 

Methodology....................................................................................................................... 7 

Tested vehicles and emissions control technologies....................................................... 7 

Vehicles and engines................................................................................................... 7 

Control technologies ................................................................................................... 8 

Fuel formulations...................................................................................................... 18 

Isolated zone testing...................................................................................................... 22 

Test site ..................................................................................................................... 23 

Duty cycles................................................................................................................ 27 

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

analysis.......................................................................................................................... 28 

Sampling and measurement methodology................................................................ 35 

Sampling strategy...................................................................................................... 38 

Normalization procedure .............................................................................................. 38 

Adjusting (normalizing) for ventilation.................................................................... 39 

Control technology efficiency calculations using normalized concentrations ......... 40 

Normalizing to CO2 .................................................................................................. 41 

Exhaust emission testing............................................................................................... 42 

Engine operating conditions ..................................................................................... 42 

Equipment, instrumentation, and methods for measurement of exhaust pipe 

emissions................................................................................................................... 43 

Results and Discussion ..................................................................................................... 44 

Ventilation rates............................................................................................................ 44

The effects of control technologies on elemental carbon concentrations..................... 49 

The effects of control technologies on concentration of total particulate matter (TPM) 

under 0.8 :m................................................................................................................. 51 

The effects of control technologies on count and size distribution of particles............ 53 

The effects of control technologies on ambient concentrations of carbon monoxide 

(CO), carbon dioxide (CO2), nitric oxide (NO), and nitrogen dioxide (NO2) .............. 61 

Carbon monoxide (CO)............................................................................................. 62 

Carbon dioxide (CO2) ............................................................................................... 62 

Nitric oxide (NO)...................................................................................................... 65 

Nitrogen dioxide (NO2)............................................................................................. 66 

Analysis of exhaust temperature and back pressure data.............................................. 69 

Results of the Tailpipe Emissions Measurements ........................................................ 75 

Particulate matter emissions, Elemental Carbon ...................................................... 75 

Particulate matter emissions, Bacharach Smoke Numbers....................................... 76 

Emissions of carbon monoxide, carbon dioxide, nitric oxide, and nitrogen dioxide 77 

Implementation of the DPF Systems ........................................................................ 82 

References......................................................................................................................... 86 
2

Table of Figures 

Figure 1. Engelhard DPX DPF system on the truck #92128 ............................................ 11 

Figure 2. CleanAir Systems DPF System on the truck #92133........................................ 12 

Figure 3. DCL BlueSky DPF System on the LHD #92506 .............................................. 13 

Figure 4 . Mac’s Mining Repair/Donaldson P604516 filtration system on the LHD 

#92506....................................................................................................................... 14

Figure 5. ECS Cattrap DPF system on the LHD #92526 ................................................. 16 

Figure 6. DCL MineX Sootfilter® DPF System on the haul truck #99942 ..................... 17 

Figure 7. Mixing and storage vessels for B20 and B50 biodiesel #2 diesel fuel blends .. 19 

Figure 8. Fueling station in isolated zone ......................................................................... 21 

Figure 9. Isolated zone, 52E entry, Stillwater Nye Mine.................................................. 24 

Figure 10. The isolated zone and duty cycles for the trucks #92128, and #92133........... 25 

Figure 11. The isolated zone and duty cycle for the LHDs #92506, #92526, and #99942

................................................................................................................................... 26 

Figure 12. The high volume DPM sampling train ............................................................ 30 

Figure 13. Downstream sampling station showing instrumentation and grid supporting 

DPM samplers, anemometer, iTX gas monitor ........................................................ 34 

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

high volume sampling heads (in triplicate) and three standard samplers ................. 37 

Figure 15. Ventilation rates for the tests involving #92128.............................................. 44 

Figure 16. Ventilation rates for the tests involving #92133.............................................. 45 

Figure 17. Ventilation rates for the tests involving #92506.............................................. 45 

Figure 18. Ventilation rates for the tests involving #92526.............................................. 46 

Figure 19. Ventilation rates for the tests involving #99942.............................................. 46 

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

#99942 (5/29/03)....................................................................................................... 52 

Figure 21. Size distribution of aerosols in mine air for truck #92128 - Engelhard DPX 

DPF vs. Muffler ........................................................................................................ 55 

Figure 22. Size distribution of aerosols in mine air for LHD #99942 - DCL MineX vs. 

Muffler ...................................................................................................................... 56

Figure 23. Size distribution of aerosols in mine air for truck #92506 equipped with 

muffler - Fuel 1 vs. Fuel 2 ........................................................................................ 57 

Figure 24. Size distribution of aerosols in mine air for LHD #92526 - Engelhard 

PTX/Muffler vs. Muffler .......................................................................................... 58 

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

(Engelhard PTX) and muffler - #2 diesel vs. Biodiesel B20 vs. Biodiesel B50....... 59 

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

muffler - #1 diesel vs. #2 diesel................................................................................ 60 

Figure 27. Normalized CO2 concentrations for the tests with LHD #92506.................... 63 

Figure 28. Normalized CO2 concentrations for tests the LHD #92526 ............................ 64 

Figure 29. Normalized CO2 concentrations for the tests with LHD #99942.................... 64 

Figure 30. Normalized NO concentrations for the tests with LHD #92526 ..................... 65 

Figure 31. Normalized NO concentrations for the tests with LHD #99942 ..................... 66 

Figure 32. Normalized NO2 concentrations for the tests with haul truck #92128............ 67 

Figure 33. Normalized NO2 concentrations for the tests with LHD #99942.................... 67 
3

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

for the tests with LHD #99942.................................................................................. 68 

Figure 35. Vehicle exhaust temperature and backpressure log during the isozone test run

................................................................................................................................... 71 

Figure 36. Temperature frequency distribution and “more than” type cumulative 

frequency distribution used to determine T30............................................................ 72 

Figure 37. Exhaust T and BP during emissions testing showing DPF regeneration ........ 73 

Figure 38: Reduction of EC emissions at TCS mode ....................................................... 76 

Figure 39. NO Emissions in TCS mode ........................................................................... 80 

Figure 40. NO2 Emissions in TCS mode .......................................................................... 82 
4

Table of Tables 

Table 1. The vehicles and DPF systems from Stillwater inventory equipped with DPF 

systems prior to the study ........................................................................................... 9 

Table 2. The vehicles from Stillwater Nye mine inventory that were retrofitted with DPF 

systems as part of the study ...................................................................................... 10 

Table 3. Results of fuel analysis ...................................................................................... 20 

Table 4. Fuel used in this study ........................................................................................ 21 

Table 5. List of the tests performed in the isolated zone .................................................. 23 

Table 6. Average ventilation rates normalized with respect to MSHA ventilation rates and 

contribution of the tested vehicles/configurations to concentrations of carbon 

dioxide at downstream sampling station................................................................... 47 

Table 7. Elemental carbon results normalized with respect to ventilation rates............... 50 

Table 8. Elemental carbon results normalized with respect to CO2 concentrations ......... 50 

Table 9. Concentrations of TPM under 0.8 :m the downstream sampling station ......... 51 

Table 10. Effects of control technologies on concentration of aerosols in mine air......... 53 

Table 11. Normalized concentrations of carbon monoxide (CO), carbon dioxide (CO2), 

nitric oxide (NO), and nitrogen dioxide (NO2) at downstream sampling station ..... 61 

Table 12. Results of the on-board temperature and exhaust backpressure logs ............... 69 

Table 13 : Effects of control technologies on elemental carbon emissions...................... 75 

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

................................................................................................................................... 77 

Table 15. CO concentrations............................................................................................. 78 

Table 16. CO2 concentrations ........................................................................................... 78 

Table 17. NO concentrations ............................................................................................ 79 

Table 18: NO2 concentrations........................................................................................... 81 

Table 19. Costs and installation issues related to implementation of DPF systems......... 82 

 

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

NIOSH.
5

Introduction 

This study is organized under the auspices of the Metal/Nonmetal Diesel Partnership 

formed by the National Institute of Occupational Safety and Health (NIOSH), the 

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

(NSSGA), the United Steel Workers of America (USWA) and the MARG Diesel 

Coalition. The ultimate objective of the study is to reduce the exposure of underground 

miners to diesel particulate matter (DPM) and gases, and to help in fulfilling the 

partnership’s goal of identifying technically and economically feasible controls to curtail 

particulate matter emissions from existing and new diesel powered vehicles in 

underground metal and nonmetal mines. 

The majority of current knowledge on the performance of the diesel particulate filter 

(DPF) systems and other control technologies is based on studies done under laboratory 

conditions, the results then being applied the results to on-highway vehicles. According 

to the best knowledge of the authors, only two comprehensive studies that were 

conducted recently at Noranda’s Bathurst Mining and Smelting Mine and International 

Nickel Company’s Stobie Mine under the sponsorship of the Diesel Emissions 

Evaluation Program [McGinn 2001, Bugarski and Schnakenberg 2001, Bugarski and 

Schnakenberg 2002] offered some insight into the problems associated with the 

deployment of modern DPFs to underground mining vehicles. The U.S. mining industry 

has expressed concern that this rather limited knowledge base is not sufficient to help 

them comply with the rule limiting DPM exposure of underground metal and nonmetal 

miners [30 CFR 57.5060 2001]. 

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

several underground mines was needed to determine their viability of DPF systems and 

establish confidence in their performance. The first in this series of studies was the one 

conducted in Stillwater Mining Company’s Nye Mine, Nye, Montana. This study was 

conducted in two phases. The objective of the first phase was to establish the 

effectiveness of the selected technologies in reducing diesel emissions by using an 

isolated zone methodology. The objective of the second phase was to assess the 

effectiveness of diesel particulate filters in controlling the exposure of underground 

miners in actual production scenarios. As part of the first phase of the study a series of 

tests were conducted at Nye Mine from May 19, 2003 until May 30, 2003. The results of 

Phase I of the study are presented in this report. 
6

Objectives 

The objective of the 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. The protocol was established to 

determine the effectiveness of those technologies in an underground environment under 

operating conditions that closely resemble actual production scenarios. 

 

This study was designed to provide Stillwater, and the general mining community, with 

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

the appropriate devices for reducing diesel emissions. The focus of the Stillwater 

research was on technologies that offer solutions for reducing DPM emissions. This 

report provides the results and assessment of the following control technologies: diesel 

particulate filters, disposable paper 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 other important issues related to the 

implementation and operation of DPFs, namely regeneration of DPF systems during the 

production cycle, their reliability and durability. Addressing these issues will require 

long-term studies with continuous monitoring of performance of the DPF systems and 

periodic emissions testing. 

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

technologies on concentrations of DPM and gases in the mine air. The majority of this 

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

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

made to assess the effect of blended biodiesel, # 1 and #2 diesel fuels, and of selected 

diesel oxidation catalysts (DOC) on air quality and emissions. 

The primary thrust of this study was the series of the measurements of ambient 

concentrations of DPM and gases in an isolated zone in the mine while each of the tested 

vehicles was performing a structured, repeatable duty cycles within that isolated zone. 

This part of the study was executed in the isolated zone of the 52E drift of Stillwater Nye 

mine. 

The ambient measurements were complemented with measurements of DPM and gas 

concentrations in the exhaust system of the tested vehicles while the vehicles were parked 

and their engines were loaded under stationary conditions. This part of the study was 

conducted in the surface equipment repair shop at the Nye mine. 

The study was conducted by researchers from NIOSH and Stillwater Mining Company 

with representatives of the partnership and MSHA present during some portions of the 2-

week effort. 
7

Methodology 

Tested vehicles and emissions control technologies 

Vehicles and engines 

Stillwater Mining selected the diesel equipment to represent typical vehicles and power 

packages from the Stillwater Nye mine production fleet. The selected vehicles, two trucks 

and three load-haul-dump vehicles are classified as heavy-duty production machines. 

These vehicles were selected to be 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. 

The 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) is a truck with 

rated load of 14545 kg (32000 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 BF6M 1013ECP. 

 

MTI LT-350 load-haul-dump #92506 

MTI LT 350 (Mining Technologies International, Sudbury, Ontario) is a load-haul-dump 

with rated load of 3409 kg (7500 lb) and bucket capacity of 1.9 m3

 (2.5 yd3). This model 

is powered by a Deutz BF4M 1013C. 

Caterpillar Elphinstone R1300 load-haul-dump #92526 

Caterpillar Elphinstone R 1300 (Caterpillar Elphinstone PTY LTD, Burnie, Tasmania, 

Australia) is a load-haul dump vehicle with rated load of 6500 kg (14333 lb) and bucket 

capacity of 2.8 m3

 (3.7 yd3). This particular vehicle is powered by a Caterpillar CAT 

3306 DITA engine derated to 123 KW (165 HP). In Stillwater Nye mine the #92526 and 

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

Caterpillar Elphinstone R1500 load-haul-dump #99942 

Caterpillar Elphinstone R 1500 (Caterpillar Elphinstone PTY. LTD, Burnie, Tasmania, 

Australia) is a load-haul dump vehicle with a rated load of 10200 kg (22491 lb) and 

bucket capacity of 4.8 m3

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

DITA engine rated at @ 164 KW (220 HP). In Stillwater Nye mine the #99942 and 

similar vehicles are typically used at a draw point for loading MTI DT 1604 trucks. 
8

Preparation of the vehicle for the study 

The major modifications on the vehicles/engines were those related to removal of 

oxidation catalytic converters for the purpose of establishing engine baseline emissions 

and the modifications required to install the DPF systems. The catalytic converters were 

temporarily removed from the vehicles and replaced with an adequate muffler. The other 

modification was to install a system to capture crankcase breather effluent on those 

engines that need it to eliminate that source of emission during control system 

evaluations. The Deutz BF4M1013 and BF6M1013 engines, which powered three of the 

tested vehicles (#92128, #92133, and #92506), are designed with a closed loop crankcase 

breather systems. The Caterpillar 3306 DITA engines release unfiltered crankcase 

emissions (primarily oil mist and exhaust blowby) to the atmosphere. For this study, 

Stillwater fitted the Caterpillar engine being tested with a system to filter and routed the 

crankcase blowby to the engine air intake. 

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 at Nye 

mine, the day before the vehicle was to be tested. 

Control technologies 

As previously stated, the primary objective of this study was to evaluate the effectiveness 

of six diesel particulate filtration systems on reducing the concentration of DPM in the 

underground mine environment. Additionally, the effects of replacing the currently used 

#1 diesel fuel with the blends of #1 diesel and “yellow grease” biodiesel (B20 and B50) 

and with #2 diesel were investigated. The effects of catalytic converters on diesel 

emissions were also examined. 
9

Diesel particulate filter systems 

Several state-of-the-art diesel particulate filter (DPF) systems were evaluated during this 

study. Two of the DPF systems, Engelhard DPX installed on #92128 and DCL MineX 

installed on #99942, were selected from a list of equipment already being used at 

Stillwater mine (Table 1). In addition, the other four DPF systems, CleanAir Systems 

DPF installed on #92133, DCL Blue Sky installed on #92506, Mac’s Mining 

Repair/Donaldson installed on #92506, and ECS Cattrap installed on #92526 were 

selected, retrofitted to the selected vehicle, and evaluated in this study (see Table 2). 

Table 1. The vehicles and DPF systems from Stillwater inventory equipped with 

DPF systems prior to the study 

Vehicle 

# Vehicle Type Engine 

Manufact. 

Engine 

Model 

Vent 

Rate 

[cfm] 

DPF 

Manufact. 

DPF 

Model 

DPF 

Brand 

Name 

DPF 

Media 

Type 

DPF 

Media 

Size 

[in X in] 

DPF 

Regeneration 

91580 Locomotive Deutz BF6M 

1013FC 12,000 Engelhard 9308 DPX Cordierite 10.5X12 platinum washcoat 

91582 Locomotive Deutz BF6M 

1013ECP 12,000 Engelhard 9308 DPX Cordierite 10.5X12 platinum 

washcoat 

92054 WAGNER ST2D LHD Deutz BF4M 

1013 FC 8,000 DCL 5C57 

11 

MINEX Cordierite 9X12 platinum 

washcoat 

92122 MTI DT-1604 

haul truck Deutz BF4M 

1013FC N/A Engelhard 9308 DPX Cordierite 10.5X12 platinum 

washcoat 

92128 MTI DT-1604 

haul truck Deutz BF6M 

1013FC 12,000 Engelhard 9308 DPX Cordierite 10.5X12 platinum 

washcoat 

92130 MTI DT-1604 

haul truck Deutz BF6M 

1013ECP 12,000 Engelhard 9308 DPX Cordierite 10.5X12 platinum 

washcoat 

92131 MTI DT-1604 

haul truck Deutz BF6M 

1013ECP 12,000 Engelhard 9308 DPX Cordierite 10.5X12 platinum 

washcoat 

92135 MTI DT-1604 

haul truck Deutz BF6M 

1013ECP 12,000 Engelhard 9308 DPX Cordierite 10.5X12 platinum 

washcoat 

92140 EJC 515 haul 

truck Deutz BF6M 

1013ECP 12,000 Engelhard 9308 DPX Cordierite 10.5X12 platinum 

washcoat 

92535 ELPHINSTONE 

R-1300 LHD CAT 3306 

DITA 10,000 DCL 5C57 

11 

MINE 

X Cordierite 9X11 platinum 

washcoat 

92608 MTI LT-270 

LHD Deutz BF4M 

1012C 6,500 DCL 5C57 

11 

MINE 

X Cordierite 9X12 platinum 

washcoat 
10

Table 2. The vehicles from Stillwater Nye mine inventory that were retrofitted with 

DPF systems as part of the study 

Vehicle 

# Vehicle Type Engine 

Manufact. 

Engine 

Model 

Vent. 

Rate 

[cfm] 

DPF 

Manufact. 

DPF 

Model 

DPF 

Type 

DPF 

Media 

DPF 

Media 

Size 

[in x in] 

DPF 

Regenerati

on 

Concept 

92128 MTI DT-1604 

haul truck Deutz BF6M 

1013FC 12,000 Engelhard DPX Cordierite 10.5 X 10 platinum 

washcoat 

92133 MTI DT-1604 

haul truck Deutz BF6M 

1013ECP 12,000 Clean Air 

Systems 

FPA 

158W - Cordierite 11.25X 

14 

platinum 

washcoat 

+ Ce-Pt 

fuel borne 

catalyst 

92506 MTI LT-350 

LHD Deutz BF4M 

1013C 11,500 DCL 

3211-

SA6CG1-

21 

BlueSky Silicon 

carbide 

10.5" X 

10" 

catalyzed 

+ on-board 

electrical 

regenerati

on 

92506 MTI LT-350 

LHD Deutz BF4M 

1013C 11,500 Donaldson P6045

16 - 

High 

temp. 

disposable 

disposable 

washable 

92526 Elphinstone 

R-1300 LHD CAT 

3306 

DITA 

(165 hp) 

10,000 ECS CT28 Cattrap Cordierite 

base metal 

washcoat 

+ offboard 

electrical 

regenerati

on 

99942 Elphinstone 

R-1500 LHD CAT 

3306 

DITA 

(220 hp) 

15,000 DCL 5C57 

11 MineX Cordierite 9X11 platinum washcoat 

Engelhard DPX DPF System 

The Engelhard DPX® DPF (Engelhard Corporation, Iselin, New Jersey) (Figure 1) uses a 

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

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

during an engine’s duty cycle if the exhaust temperature is over 350 °C for an extended 

period (at least 30 % of the engine’s operating time) of the cycle. Although the system is 

designed primarily for control of diesel particulate matter emissions, significant 

reductions in emissions of carbon monoxide and unburned hydrocarbons are expected 

due to a significant presence of the platinum-based catalyst. As some recent studies 

suggested [Schnakenberg and Bugarski, 2001], platinum washcoated filters are found to 

promote the (undesired) oxidation of nitric oxide to nitrogen dioxide. Such DPFs should 

be carefully considered prior to their use in underground mining applications. Although 

several similar systems were used on the production vehicles at Nye mine for extended 

periods of time, NO2 emissions have not been quantified by mine personnel and had not 

been found to be a serious problem in the prevailing ventilation. 
11

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

CleanAir Systems DPF System 

The CleanAir Systems DPF system (CleanAir Systems, Santa Fe, New Mexico) (Figure 

2) uses a Corning cordierite wall-flow monolith filter element which has been 

“washcoated” with a proprietary platinum-based catalyst. The system is used in 

conjunction with a fuel additive (Clean Diesel Technology, Stamford, Connecticut, 

Platinum Plus DFX-DPF) a bimetallic catalyst that contains both platinum and cerium 

which allows it to be used effectively at a dosage level substantially lower than other fuel 

borne catalysts. Theoretically the system, with this fuel-borne catalyst, should passively 

regenerate during the engine’s duty cycle if the exhaust temperature is over 330 °C for 

extended periods (at least 30 % of the operating time) of the cycle. The system was 

designed to provide DPF regeneration for duty cycles having relatively low exhaust 

temperatures. According to the manufacturer this system should not significantly increase 

nitrogen dioxide emissions. 

The fuel additive was mixed into the fuel tank of the #92133 during the fueling. The 

recommended dosage of 30 ounces for 125 gallons of fuel was used. 

The system was delivered several weeks prior to the study and had accumulated 

approximate 200 hours of run time prior to the testing. 
12

Figure 2. CleanAir Systems DPF System on the truck #92133 

DCL BlueSkyTM DPF System 

The DCL BlueSkyTM (DCL International, Concord, Ontario) system (Figure 3) is 

designed as an active system that does not completely regenerate during the duty cycle 

and therefore requires periodic removal of soot using integral electrical heaters and an 

off-board regeneration station to provide controlled heater power and compressed air for 

soot combustion. During the regeneration process the vehicle needs to be parked next to 

the regeneration station that is connected to power and compressed air supplies. The 

system uses a silicon carbide wall-flow monolith filter element that allows relatively 

short 2-hour regenerations. The frequency and length of regeneration sessions is 

dependant on engine DPM emissions which depend upon engine design, condition, and 

nature of the duty cycle. 

This particular system was made available for this study by the Stillwater East Boulder 

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

because of the inability of operators to regenerate the DPF due to failed heating elements. 

The heating elements were replaced, and the system was installed on LHD #92506 (see 

Figure 3). Owing to the limited space available on the vehicle, this system was installed 

with a temporary arrangement and used only during the evaluation in the isolated zone 

and shop. The system was removed immediately after the tests, and it was not evaluated 
13

in the production because, in part, the mine was unable to provide the necessary 

infrastructure in production zones to support electrically regenerated systems. 

Figure 3. DCL BlueSky DPF System on the LHD #92506 

Mac’s Mining Repair/Donaldson P604516 Filtration System 

This filtration system is in the developmental stages and uses two Donaldson P604516 

(Donaldson Company Inc, Minneapolis, Minnesota) high temperature disposable filter 

elements. Two filter elements were evaluated as part of a temporary setup that was 

custom fitted to the Deutz BF4L1013 engine that powered the LHD #92506 (Figure 4). 

Since these filter elements were designed to handle between 300 and 400 scfm of exhaust 

it was necessary to fit two filter elements in parallel to handle the engine exhaust flow 

rate. The elements were fitted into dual stainless steel canisters designed and built by 

Mac’s Mining Repair, Huntington, Utah. 
14

Figure 4 . Mac’s Mining Repair/Donaldson P604516 filtration system on the LHD 

#92506 

The filter element is a deep bed filter that collects particulate matter throughout its entire 

depth. The filter medium has a high porosity or permeability and generates relatively low 

exhaust backpressure when new. The medium is resistant to heat, water, and/or other 

combustion by-products. Specifications of the filter sub-components provide for 

appropriate levels of product durability at varying time and temperature levels. Though 

not specifically endorsed by the manufacturer, the filter may be cleaned allowing for 

limited re-use. At the time of the study, the filter elements and medium were at 

development stage and they were not available on the market. The filtration system was 

removed from #92506 shortly after the trial. The filter was not run prior to the test 

(degreened) and one could expect it to show lower filtration efficiencies in the first hour 

than for the remaining hours of its life. 

ECS CattrapTM DPF System 

ECS (Engine Control Systems, Newmarket, Ontario) designed the CattrapTM system 

(Figure 5) as a retrofit to the load-haul-dump #92526. It is a passive system that uses a 

base metal catalyst coated cordierite monolith which would partially regenerate during 

engine operation but might also require periodic cleaning, using the ECS CombiClean TM 

regeneration station. Theoretically the system should passively regenerate during the duty 

cycle if the exhaust temperatures are over 390 °C for a significant portion (at least 30 %) 
15

of the engine operating time. The frequency of the periodic cleaning is dependant on the 

ability of this system to regenerate during the cycle. The exhaust temperature traces 

generated during the pre-selection period indicated that exhaust temperatures were 

sufficient over the duty cycle of #92526 to support almost complete regeneration. The 

manufacturer predicted that cleaning would be necessary approximately every 250 hours, 

the same period as scheduled preventive maintenance sessions, but 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 CombiCleanTM cleaning station consists of a vacuum that effectively removes 

soot and ash from filters without allowing any contaminants to escape into the air 

followed by a controlled thermal regeneration using electric heaters. The filter needs to 

be removed from the vehicle and placed on the cleaning station. The complete cleaning 

process takes approximately eight hours because of the thermal sensitivity of the 

cordierite DPF element. 

The DPF system tested at #92526 included a diesel oxidation catalyst (DOC) mounted 

downstream of the DPF. The DOC is designed to reduce emissions of carbon monoxide 

and unburned hydrocarbons. 

The system was delivered and installed during the first week of testing. Therefore, the 

system had only approximately two days in the service prior to testing. The system was 

decommissioned shortly after the trial. 
16

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

DCL MineX SOOTFILTER® DPF System 

DCL MINE-X SOOTFILTER® DPF system (DCL International, Concord, Ontario) 

(Figure 6) that was tested on LHD #99942 uses a platinum wash-coated cordierite filter 

element. This system is very similar to the Engelhard DPX DPF system and, in general, 

they should behave similarly. 
17

Figure 6. DCL MineX Sootfilter® DPF System on the haul truck #99942 

The DCL DPF system was initially installed and had accumulated approximately 800 

hours on vehicle #92535. After the system failed to passively regenerate over the 

production cycle of #92535, it was cleaned and reinstalled on LHD #99942. 

DPF selection rationale 

NIOSH and the partners desired to obtain data on the filtration media used in 

commercially available DPFs and a novel disposable medium which showed promise. 

The media were the following: 1) a cordierite wallflow monolith from Corning used by 

Engelhard DPX, CleanAir Systems, ECS Cattrap, and DCL Mines, 2) a silicon carbide 

wallflow monolith from Ibiden used by DCL for BlueSky), and 3) disposable high 

temperature pleated “paper” medium from Donaldson. The detailed description of the 

cordierite and silicon carbide monolith media is available elsewhere [Schnakenberg and 

Bugarski 2002, DieselNet]. A short description of the Donaldson medium is given in the 

section on the Mac’s Mining Repair/Donaldson P604516 Filtration System. 

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

active regeneration schemes. The Engelhard DPX, DCL Mines, and CleanAir Systems 

DPF systems are passive systems. The CleanAir Systems DPF was selected because it 

showed promise of having wide applicability because of its low regeneration temperature. 

It uses a unique combination of a light wash-coat of a platinum-based catalyst and a 

cerium-platinum-based fuel borne catalyst. The system presented a viable alternative to 

platinum-catalyzed DPF systems such as Engelhard DPX and DCL MineX that are 

known for their tendency to increase secondary emissions of nitrogen dioxide. The DCL 
18

BlueSky system is an active system which required the off-shift return of the vehicle to a 

regeneration station. This and similar active DPF systems have been rejected so far by 

mine operators on the presumption that their operation would be excessively complicated 

and demanding. The ECS Cattrap can be generally classified as a active/passive system, 

because, although it requires regeneration, the period of regeneration corresponds to 

regular engine maintenance and poses little operational burden. The Mac’s Mining 

Repair/Donaldson P604516 uses two disposable filters and may be washed but is 

intended to be replaced, not regenerated. Coal mine tests are reporting 100 hours of 

operation before the filter needs to be replaced or washed. 

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

production for at least two days prior to the 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. 

The mine has been successfully operating passive DPF systems on heavy-duty trucks that 

were generally experiencing higher engine loads. Their experience with medium and 

light-duty vehicles has not been as positive because passive DPF systems installed on 

such vehicles have failed to reliably regenerate. Therefore, mine officials have been 

intensively searching for a solution for these vehicles. 

Fuel formulations 

All the diesel-powered vehicles used in underground operations at Stillwater Nye mine 

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

particular fuel exceeds MSHA requirements [30 CFR 57. 5065 1995] for diesel fuels used 

in underground mines. #1 diesel is significantly more expensive than #2 diesel. Using #1 

instead of # 2 diesel was part of the mine’s efforts to reduce exposure of underground 

miners to diesel emissions. At the request of the mine, NIOSH included a test of #2 diesel 

fuel. 

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

Kentucky (Biodiesel G 3000). The B20 and B50 blends were made at the surface shop at 

the Nye mine. The quantities of #2 diesel and neat biodiesel in the blends were 

determined volumetrically. 
19

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

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

Stillwater Nye mine was supplied from the same refinery as #1 diesel. 
20

The fuel samples of #2 diesel, B20 (20% biodiesel and 80 % #2 diesel) and the selected 

fuels were sent for detailed analysis to Southwest Research Institute (SwRI), San 

Antonio, Texas. The selected properties of the fuels are summarized in columns 4 

through 6 in Table 3. The Cenex refinery provided some limited data on the properties of 

their fuels supplied to the Nye mine (see Error! Reference source not found. columns 7 

and 8). Griffin Industries also provided a certificate of the analysis for the biodiesel 

G3000 they supplied. Some of the information from the certificate is included in Table 

3Error! Reference source not found. (see column 9) 

Table 3. Results of fuel analysis 

SwRI Cenex Griffin Type of 

analysis Method Units #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 

Hydrocarbon 

Type 

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 

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 

difference % wt. NA 2.49 5.56 N/A N/A N/A 

Heat of 

Combustion 

ASTM 

D240 

BTU/ 

lb 18335 17853 17164 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 NA 2.61 3.25 N/A N/A 4.65 

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

isolated zone in a sealed-off crosscut about halfway in the test course on 52E. 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, 

Wichita, Kansas). The reservoirs on the tested vehicles were filled to the same level prior 

to and after each test. The measured values were used to estimate fuel consumption of the 

tested vehicles. 

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

metering system (Max Machinery, 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 an excess of fuel was supplied to those 
21

engines for the purpose of cooling the cylinders. The electrical components of the fuel 

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

Figure 8. Fueling station in isolated zone 

The initial plan was to fill the 500-gallon 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 estimated 

percentages of #1 and #2 diesel fuels in the #1diesel/#2 diesel blends supplied to the test 

vehicles are given 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 tests involving LHD #99942 were run after the mistake with filling the supply tank 

with #2 diesel was discovered. The appropriate fuels were dispensed to the reservoir 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) 

and these tests can serve to demonstrate the repeatability of the isozone test method. The 

effects of the two fuels on the emissions were examined during the tests involving 

#99942 but this time with fuel from the verified source. 

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 
22

Vehicle Test Exhaust System 

Configuration 

Date Fuel 

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 

Disposable DPF 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 DOC 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 DOC and muffler 05/28/03 #2 (80.0%) / bio (20%) diesel 

#92526 

Biodiesel B50 DOC 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 MineX 05/29/03 #1 (100%) diesel 

The 1-gallon biodiesel fuel samples for the analysis at SwRI (San Antonio, Texas) were 

collected from the 55-gallon drums containing B20 and B50 blends. A sample of #2 

diesel fuel was also collected for the similar analysis conducted by SwRI 

Griffin Industries also provided a certificate of analysis for the biodiesel G3000 they 

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

9) 

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 concentrations and 

corresponding exposures, and 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. In addition, these tests were not compromised by artifacts usually 

generated in 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 loaded by vehicles and controlled by 

humans rather than by tightly controlled loads provided by an 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 

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 with the 
23

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 the 10-day study are listed in Table 5. 

Table 5. List of the 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 DPF s with 

fuel 1 

Muffler 05/23/03 Chad 

Baseline for DPF s 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 MineX 05/29/03 John 

Test site 

The 1750-ft (533 m) isolated zone was located in 52E ramp in the east section of the 

Stillwater Nye Mine. The upstream end of the zone was situated approximately 492-ft 

(150 m) from the portal. The elevation of the portal is approximately 5000 ft (1525 m) 

above see 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 12 ft (3.6 m) by 9 ft (2.7 m). The ramp has a 9% rise towards the 

downstream end. 
24

Figure 9. Isolated zone, 52E entry, Stillwater Nye Mine 

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

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

is used. 

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

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

4. The zone is sufficiently long and the opening is relatively small to ensure 

thorough air mixing at planned ventilation rates and uniform contaminant 

distribution across the drift at the downstream sampling station. 

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

maintenance during the tests. 

6. Power to operate 117VAC instruments is available at the downstream and 

upstream sampling stations. 

The schematic of the isolated zone is shown in Figure 10 and Figure 11. The tested 

vehicles were operated over the simulated duty cycles between the upstream and 

downstream load/dump points that were approximately 1000 feet (305 m) apart. The 

upstream sampling station was located approximately 300 ft (91 m) upstream of the 

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

450 ft (137 m) downstream of downstream sampling station. A third sampling point was 

located on the vehicle. The ventilation control doors were located approximately 200 ft 

(61m) downstream of the downstream sampling station. The refueling station was located 

in one of the sealed stopes half way between upstream and downstream load/dump 

points. Significant quantities of waste rock, sufficient to sustain duty cycle for LHD 

vehicles, were available on upstream and downstream load/dump points. 
25

Figure 10. The isolated zone and duty cycles for the trucks #92128, and #92133 
26

Figure 11. The isolated zone and duty cycle for the LHDs #92506, #92526, and 

#99942 
27

Duty cycles 

NIOSH and Stillwater Nye mine personnel, including experienced vehicle operators, 

developed two defined, conservative, simple and repeatable duty cycles, one for haul 

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

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 events occurring between those points. The trucks were operated with 

a 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 the 

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 at which time a new cycle would start. 

Two full cycles, designated as warm-up cycles, were executed during each test prior to 

the start of sampling at each of the three stations. The warm-up cycles allowed the driver 

to become familiar with the cycle and to allow some build up of pollutants prior to 

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

cycles. The duration of a complete duty cycle for trucks averaged eight minutes. The 

length of each test was dictated by the required time to acquire an adequate DPM sample 

for EC analysis. 

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

tests (see Table 5). This practice reduced potential error due created by 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 events 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 lengths of the vehicle up the ramp. At 

that location the operator would engage the hydraulics to simulate loading of an 
28

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 LHS would execute three 

load/dump tasks similar to that 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. 

In each test, two full warm-up cycles were executed prior to the start of sampling. The 

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

the duty cycle for LHDs averaged thirteen minutes. The length of the tests was dictated 

by the required time for DPM sampling. 

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

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

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

with DCL BlueSky. 

Equipment, instrumentation, and methods for ambient sampling, 

measurements, and analysis 

The description of various equipment, instrumentation, and methods used in this study to 

collect particulate samples or directly measure concentrations of particulates and selected 

gases is given below. 

Standard DPM sampling method 

The sampling train used for DPM sampling was identical to the one used by Mine Safety 

and Health Administration (MSHA) for DPM compliance monitoring [66 Fed. Reg. 5706 

and corrections 66 Fed. Reg. 35518 2001]. It consisted of a flow controlled MSA Elf 

Model pump from Mine Safety Appliances Company, Pittsburgh, PA, a 10 mm DorrOliver cyclone, and an SKC DPM cassette from SKC, Inc., Eighty Four, PA. The SKC 

DPM cassette contained a single stage impactor and two stacked 37 mm tissue quartz 

fiber filters. The pumps were operated at 1.7 l/m. 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 II bubble flow meter from Sensydine, 

Clearwater, FL. If the measured flow rates deviated more than 5 percent from the 1.7 lpm 

the pumps were recalibrated. 

Exposed SKC DPM cassettes were shipped to NIOSH PRL and analyzed by the NIOSH 

PRL analytical laboratory for elemental carbon content using the NIOSH 5040 Analytical 

Method. 

High volume DPM sampling procedure 

The preliminary analysis indicated that if the standard sampling procedure was used in 

the isolated zone study, extremely long sampling times would be required to collect 
29

sufficient material to obtain accurate carbon analysis using the NIOSH 5040 Analytical 

Method. Therefore, NIOSH designed a high volume sampling train (Figure 12) to 

accelerate the collection of adequate sample mass. This was accomplished by increasing 

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 USBM single stage diesel 

impactor with a 0.8 μm cut point. It was absolutely crucial to maintain flow rate of 1.7 

lpm through the cyclones and impactors in order to ensure their proper size selection 

performance. That was achieved by designing a symmetrical plenum that distributed the 

total flow rate of 8.5 lpm uniformly among the five streams. Each of the preclassifier 

assemblies was connected to a plenum chamber by a 3-foot long section of conductive 

tubing. The outlet of the plenum was directly connected to a stainless steel 25-mm filter 

holder containing two 25-mm tissue quartz fiber filters (Tissuequartz 2500QAT, Pall 

Corporation, Ann Arbor, MI) placed in tandem. 

The total sampling flow rate was controlled with Model HFC 302 mass flow controllers 

from Teledyne, Hampton VA. The mass flow controllers were calibrated by the 

manufacturer, and checked using a Gillibrator. The Model 0523-101Q high volume 

rotary vane pump from Gast Company, Benton Harbor, MI, was used to pull the sample 

though the filter. 

The three-way valve and bypass line incorporated in the system allows steady operation 

of the mass flow controller and pump, and minimizes transient effects on sampling flow 

rates while facilitating the initiation and termination of sampling. 
30

Figure 12. The high volume DPM sampling train 
31

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 a continual read-out of concentrations of total 

particulate matter (TPM) under 0.8 :m. One was located at the upstream station, the 

other at the downstream sampling station. The 10 mm Dorr-Oliver cyclone and USBM 

diesel impactor with a 0.8 μm cut-off were used as pre-classifiers. The sampling flow rate 

of 1.7 lpm was maintained throughout the study 

The TEOM is a gravimetric instrument that draws air through a filter at a constant flow 

rate, while continuously weighing the filter and calculating near real-time mass 

concentrations. The tapered element is the heart of the mass detection system. The 

tapered element is in essence a hollow cantilever beam that supports a mass (the sample 

filter) and oscillates at a frequency that depends on the spring constant of the tapered 

element and the mass, a disposable filter element, at its free end. The sample stream is 

drawn through this filter from the hollow tapered element which is connected to the 

suction side of the sampling system. As particulate mass collects on the filter, the 

vibration frequency of the tapered element decreases. By frequent measurements of the 

tapered element frequency, the TEOM calculates the increase in mass that has 

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

accumulated mass by the volume of air flow 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. The 

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

ambient temperatures. 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 is maintained at 50 °C 

During this study the flow rate on both the upstream and downstream TEOM was set at 

1.7 liters per minute. A cyclone and impactor were used as preclassifiers to the TEOM 

allowing only particles with average aerodynamic diameter (D50) smaller that 0.8 :m. 

The average ambient concentrations of TPM were recorded and saved every 10 seconds. 

The reported concentrations were averaged over the periods required to collect particulate 

samples for carbon analysis using high volume sampling methodology. 

Measurement of size distribution and particle numbers using a scanning mobility 

particle sizer 

The scanning mobility particle sizer (SMPS) Model 3926 from TSI Inc., St. Paul MN, 

consisting of an electrostatic classifier Model 3080L and a condensation particle counter 

(CPC) Model 3025A, was used at the downstream sampling station to periodically 

measure size distribution and number of particles in the range between 10 and 392 nm. 
32

The flow of monodispersed aerosol was maintained at 0.6 lpm throughout the study. The 

sheet flow was maintained at 6.0 lpm. At the established polydispersed aerosol flow rate 

the inlet impactor had a cut-off point of 0.46 μm. The CPC was operated in high-flow 

mode to minimize diffusion losses. The samples were collected using 90-second up-scan 

and 15-second down-scan. The instrument was operated using a dedicated laptop 

computer and Aerosol Instrument Manager Software (TSI Inc. St. Paul, MN). 

Although the duty cycles for all tested vehicles were extremely transient, the resulting 

aerosol distributions in the mine air were made quasi-steady by relative movements of the 

vehicles and ventilation air. The effects of the technologies on size distribution and count 

concentrations of aerosols in mine air were assessed on the basis of the analysis 

performed on results of the measurements conducted while vehicles were performing the 

portion of the duty cycle at the downstream load/dump point, a point nearest the location 

of the SMPS. 

The distributions and count concentrations were found to be extremely dependent on the 

position of the vehicles relative to the instrument. 

Concentration of O2, CO, NO and NO2 measured by an Industrial Scientific iTX 

multi-gas monitor 

The ambient concentrations of carbon monoxide, nitrogen dioxide and nitric oxide were 

measured at all three sampling locations using iTX multi-gas monitors built by Industrial 

Scientific, Oakdale, PA. One of the iTX multi-gas monitors was dedicated to each of the 

sampling location for the duration of the isolated zone testing (iTX s/n 064-downstream 

grid, iTX s/n 065-upstream grid and iTX s/n 199-test machine operator). The ambient 

concentrations were measured every 10 seconds and stored into the monitor’s memory. 

The iTX is a diffusion gas monitor based on electrochemical cell technology. The 

instrument continuously monitors and simultaneously displays all gasses sampled. The 

data logging capability of these monitors was used during the study. 

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

provides automatic calibration and instrument diagnostics as well as maintaining 

instrument database records. 

The iTX gas monitors were (the only instruments) removed from the Isozone at the end 

of each test. On surface, the logged data was downloaded to a laptop PC after each test. 
33

Ambient concentration of CO and CO2 measured by an INNOVA 1312 

photoacoustic multigas monitor 

The ambient concentrations of carbon monoxide (CO) and carbon dioxide (CO2) at the 

downstream sampling station were measured by an INNOVA 1312 Photoacoustic Multigas Monitor (INNOVA, Naerum, Denmark). The INNOVA 1312 Photoacoustic Multigas Monitor uses a photoacoustic infrared detection method to measure CO and CO2 and 

has a limit of detection in the ppb range. During a gas concentration measurement, a 

sample of air is drawn into an analysis cell within the INNOVA. The cell is then sealed 

off and light is sent from the infra-red source via a chopper (pulsating light) through an 

optical filter. The optical filter only transmits light in a defined wavelength range and this 

light enters the cell. If there is gas in the cell which absorbs light of this wavelength, a 

pressure wave is created and this is measured by microphones mounted within the cell. 

The greater the concentration of the absorbing gas in the cell, the greater the pressure 

(sound) wave it creates. The optical filter is calibrated to measure the relationship 

between the measured sound signal and the concentration of the absorbing gas in the cell. 

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

before the study. The background CO2 concentrations were determined on the basis of 

the 12-hour measurements conducted during the night hours when there were no dieselpowered 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 memory 

approximately every 62 seconds. The stored values were downloaded to a laptop PC at 

the conclusion of every test. 

Measurements of exhaust temperature and engine backpressure 

The exhaust temperatures upstream of the DPF systems were measured continuously 

during the tests using a Model KMQSS-125G-6, K-type thermocouple from OMEGA, 

Inc. The engine backpressure was measured using a Kavlico Model P356 differential 

pressure sensor built by Kavlico Corp., CA. The output from the thermocouples and 

pressure sensor were logged at a rate of 0.2 Hz using a MiniLogger portable data logging 

system from Logic Beach, La Mesa, CA and accompanying HyperWare software. 

Measurement of ambient temperature and barometric pressure 

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

TEOM 1400a. 

Measurements of ventilation rate 

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 Limited, 

High Wycombe, England. The anemometer sensor was located in the center of the steel 

grid supporting the DPM samplers. The output from the anemometer was sampled every 
34

2 seconds. A 5-sample average was computed and stored into memory creating a log of 

10-sec averages using a MiniLogger portable data logging system from Logic Beach, La 

Mesa, CA and accompanying software from HyperWare. 

The air velocities were also measured periodically using a vane anemometer while 

conducting a moving traverse across the entry. The logged entry velocities were 

converted to air quantities by multiplying the velocity times the entry cross-sectional 

area. These resulting air quantities were used to adjust the downstream pollutant 

concentrations to a value that would prevail at the MSHA nameplate ventilation rate for 

the engine being tested. The MSHA nameplate ventilation rate is estimated quantity of 

ventilation air needed to maintain concentration of CO, CO2, NO, and NO2 emitted by the 

diesel engine bellow corresponding ACGIH TLV values for those gases. This ventilation 

rate is calculated on a basis of the emissions of aforementioned gases determined while 

engine is operated over 8 modes of ISO 8174. Normalizing the results with respect to 

MSHA ventilation rates was found to be advantageous for better understanding and easier 

comparison of the results, although metal mines including Stillwater mine are not 

required to provide this quantity of the ventilation air in their workings. 

Figure 13. Downstream sampling station showing instrumentation and grid 

supporting DPM samplers, anemometer, iTX gas monitor 

Analysis of the samples collected using standard and high volume method 

The samples that were collected on quartz fiber filters, using standard and high volume 

sampling procedures, were analyzed by the NIOSH PRL analytical laboratory for 
35

elemental carbon content using NIOSH Analytical Method 5040 [NIOSH 1999, Birch 

and Cary 1996]. 

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

from Sunset Laboratories, Forest Grove Oregon. 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 surface 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 cut-out is placed in to the oven 

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

Manual of Analytical Methods and in Birch ME and Cary RA [1996]. The temperature 

steps for the OC portion were set to 200, 450, 650, and 870 °C. Typical times at each 

temperature were increased so that peaks for both OC and EC could be fully resolved. 

 

NIOSH method 5040 analyzes for OC and EC in two different stages. In the first stage, 

the OC is measured by ramping the oven temperature over four progressively higher 

temperature steps programmed into the instrument, with the last step being at about 870 

°C in a pure helium atmosphere. The EC does not evolve because there is no oxygen for 

it to react with to form a gas to evolve at the set temperature. The evolved OC is 

oxidized to CO2, reduced to CH4, and finally measured using a flame ionization detector 

(FID). 

In the second stage, the EC is measured by reducing the oven temperature to about 600 

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

(oxygen is now present to react with the EC to form CO2). The EC is then measured in 

the same way as the OC. The NIOSH method 5040 also corrects for pyrolysis of OC and 

carbonates. 

Two types of samplers were used in the isozone study of control technologies. One was a 

high volume sampler designed by NIOSH for this study and the other was a SKC DPM 

cassette. Both samplers had two quartz filters placed in tandem. The first filter was used 

to collect particulate matter. However, the quartz filter will also adsorb vapor phase OC 

that is not particulate or part of DPM. The second filter behind the first filter was used to 

correct for this adsorbed vapor phase OC by, in theory, adsorbing the same amount of 

vapor phase OC as the first filter. The EC was only in particulate form and all of the EC 

will collect on the first filter. At this time, only the primary or first filter was analyzed. 

Sampling and measurement methodology 

Three sampling stations were established for each of the tests in the isolated zone. The 

upstream sampling station was located approximately 300 ft (91 m) upstream of the 

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

approximately 450 ft (137 m) downstream of the downstream load/dump point and 200 ft 
36

(61 m) upstream of the ventilation doors. The third sampling station was located on each 

of the tested vehicles. 

Upstream sampling station 

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

the upstream station: 

1. A standard sampling procedure was used to collect elemental carbon (EC) 

samples for carbon analysis (NIOSH Analytical Method 5040); 

2. A high volume sampling procedure was used to collect particulate samples for 

carbon analysis (NIOSH Analytical Method 5040); 

3. A TEOM Series 1400a ambient particulate monitor was used for real time 

measurements of total particulate matter under 0.8 :m; 

An iTX Multigas monitor was used on the upstream station to measure concentrations of 

carbon monoxide (CO), nitric oxide (NO) and nitrogen dioxide (NO2). 

The downstream sampling station 

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

on the downstream station: 

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

carbon analysis (NIOSH Analytical Method 5040); 

2. The high volume sampling procedure was used to collect particulate samples 

for carbon analysis (NIOSH Analytical Method 5040); 

3. The TEOM Series 1400a ambient particulate monitor was used for real time 

measurements of total particulate matter under 0.8 :m; 

4. The Scanning Mobility particle analyzer was used to measure size distribution 

and count concentrations of aerosols; 

5. A PAS 2000 real-time PAH monitor from EcoChem Analytics, West Hills, 

CA was used for real-time measurements of concentrations of polyaromatic 

hydrocarbons (PAHs) and EC. 

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

on the downstream station: 

1. The ITX Multi-gas monitor was used for real-time measurements of 

concentrations of CO, NO, and NO2 , and 

2. The INNOVA 1312 photoacoustic multigas was used for real time 

measurements of concentrations of carbon monoxide (CO) and carbon dioxide 

(CO2) 
37

The vehicle sampling station 

The vehicle sampling stations were established on the each of the sampling vehicle. The 

stations were located approximately two feet from the operator. At this sampling location 

the standard sampling procedure was used to collect particulate samples for carbon 

analysis. The iTX Multi-gas monitor from Industrial Scientific, Oakdale, PA was 

incorporated in this sampling station. It was used for real-time monitoring and recording 

of concentrations of CO, NO, and NO2. 

The distribution of the standard and high volume 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 (in triplicate) and three standard samplers 
38

Sampling strategy 

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

1. The vehicles were brought to the fueling station prior to the tests and topped 

with fuel. While the vehicles were fueled, the operator would be briefed on 

the details of the test protocol and instructed on the duty cycles; 

2. After refueling the operator would perform two warm-up cycles; 

3. At the end of the second warm-up cycle the vehicles were stopped on the 

upstream load/dump point and all particulate matter samplers and all real time 

sampling instrumentation at all three sampling stations were turned on. At that 

time the test would officially commence. 

4. The objective was to collect at least 30 :g of elemental carbon on the 

sampling filters used at the downstream sampling station. The length of the 

tests was estimated on a 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 high volume (or even the standard 

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

upstream sampling stations would be stopped and the test would be 

terminated; 

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

and high volume samples were recorded. 

6. The sampling flow rates were checked on a daily basis and, if necessary, the 

pumps were recalibrated. 

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

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 high volume 

samplers. 

Normalization procedure 

In order for one to determine the results of the application of control technology, the test 

conditions for the control and the baseline to which it is compared need to be as similar 

as possible. In our tests, the tested technology and its baseline used the same vehicle, the 

same operating cycle/scenario which we created, and the same driver when possible. We 

initially did not attempt to use the same ventilation rate, since we were measuring 

ventilation and could adjust the concentrations measured to be at the same ventilation 

rate. We recognized that there will be differences between the baseline run and the run 

using control technology. In particular we thought we would need to run the tests with the 

control technology for a much longer period and at lower ventilation rates to ensure the 

collection of sufficient sample material for analysis. We also measured the amount of fuel 

used during each test and attempted to log the real-time fuel consumption as additional 

measures to ensure the similarity of the test runs by comparing the fuel consumed per one 

complete cycle. Lastly, we measured and logged in real time the CO2 downstream of the 
39

test zone so that the average CO2 concentration could be determined for the sampling 

period over which elemental carbon was collected. 

The use of fuel consumed provides a means for adjusting the test runs to be equal in the 

amount of fuel used or energy consumed. For example, when comparing the baseline and 

control technology tests, if one of the tests used more fuel per cycle than the other, the 

concentrations of the larger would be reduced in proportion to the amount of additional 

fuel used. We have not pursued this avenue for these tests although we have the fuel 

consumption data. 

The use of simultaneously determined carbon dioxide (CO2) concentrations as a means 

for ensuring similarity of testing is perhaps the best method to ensure that the control 

technology is being compared on equal footing between baseline and test run. This 

concept originated in contract work of the Bureau of Mines and Michigan Technology 

University in the early 1980’s. The assumption is that the emissions of a particular 

pollutant (gas or DPM), when divided by the fuel used, would be a constant for a 

particular duty cycle (such as the ones we defined for the Isozone testing). The amount of 

fuel used is directly proportional to the CO2 emissions; that is, the ratio of DPM 

emissions to CO2 emissions is a constant. The relationship also includes the assumption 

that the control technology does not alter the CO2 concentration (true in our case), and the 

execution of the duty cycle is fairly consistent (the same driver for example). The major 

advantage is that both the DPM (and other pollutants) and CO2 concentrations are equally 

affected by the prevailing ventilation; hence, there is no need to measure or account for 

ventilation differences between runs. With the condition that two tests are run with 

reasonably similar duty cycles, as our tests were, CO2 provides the best parameter for 

adjusting pollutant concentrations in order to compare the effects of control technology. 

In the discussion below, all concentrations are net concentrations, that is, the 

concentration of the pollutant in the upstream air has been subtracted out. For CO2, the 

natural background of 402 ppm has been subtracted out of the concentrations. In most 

instances the upstream concentration of elemental carbon, CO, NO, and NO2 were below 

our detection limit. 

 Adjusting (normalizing) for ventilation 

The process for adjusting for ventilation differences between any two runs of the same 

vehicle can be performed in several ways. The concept is fairly easy to grasp: for a 

constant tailpipe emission rate, if the ventilation is doubled the resultant concentration is 

halved – that is, there is an inverse relationship between concentration and ventilation. 

This can be expressed mathematically in the following relation for any pollutant: 

Equation 1. Emission Rate relationship to dilution ventilation and resulting concentrations. 

ER = C1 ×V1 = C2 ×V2 = C3 ×V3 = Ci ×Vi
40

where 

ER is the pollutant tailpipe emission rate; 

Ci is the net pollutant concentration measured at ventilation Vi; and, 

Vi is the ventilation rate where the pollutant was measured. (To the degree that the 

Isozone is free of ventilation sources or leaks, this relationship holds.) 

We chose to present both the gaseous and elemental carbon concentrations adjusted to the 

MSHA nameplate ventilation rate for the engine used in any particular test run. In doing 

this, the concentrations would be presented at a known ventilation rate so they could be 

useful to others who might want to perform calculations to get the concentration at a 

different ventilation rate, and so that the concentration would be approximately 

representative of that for the prevailing ventilation rate in the workplace. Thus, for 

example, the emission rate for a baseline test, which resulted in a measured concentration 

at baseline ventilation, was converted to the equivalent concentration that would be 

measured at the MSHA nameplate rate by the following formula: 

Equation 2. Adjusting (normalizing) measured concentration to what it would be at MSHA 

nameplate ventilation rates. 

MSHA

MSHA

Test Test C

V

C V = × 

The above is applied to both the baseline and test runs for the control technology. 

Control technology efficiency calculations using normalized 

concentrations 

The basic equation for expressing the performance of a control technology to reduce a 

pollutant concentration is the following: 

Equation 3. Fundamental pollutant reduction efficiency equation based on emission rates. 

Control Tech Efficiency (%) 1 

×100%











 = −

BL

CT

ER

ER , 

where 

ERCT is the pollutant tailpipe emission rate when the control technology (CT) is 

being used; and, 

ERBL is the pollutant tailpipe emission rate without the control technology, the 

baseline (BL). 

When the concentrations are adjusted (normalized) to the same ventilation rate as they 

have to be when performing this comparison, the equation becomes (for MSHA vent 

rates) the following: 
41

Equation 4. Control efficiency using concentrations adjusted to MSHA nameplate ventilation rate. 

100%

C

C CT Efficiency (%) 1- BL

MSHA

MSHA ×













 =

CT

, 

where, 

BL

MSHA

CT CMSHA respectively represent the measur and C ed concentration for the control 

technology test run converted to its MSHA ventilation rate equivalent and the 

measured concentration for the baseline test converted to its MSHA ventilation 

rate equivalent. 

Normalizing to CO2 

As described above, Michigan Technological University espoused, and other researchers 

have used, the assumption that the emission rate of a pollutant divided by the CO2

emission rate is, on the average over vehicle operation, fairly constant. Furthermore, this 

ratio holds for measured concentrations in the ambient air and is wholly independent of 

the prevailing ventilation rate. Thus we can define a parameter, an engine-specific and 

somewhat duty cycle specific tailpipe emission characteristic for the engine, as the ratio 

of a pollutant emission rate to the CO2 emission rate. The introduction of a control 

technology largely affects the pollutant emission rate and not the CO2 emission rate in 

most cases. 

Thus the control efficiency equation becomes the following for a concentration of 

pollutant P: 

Equation 5. Control technology reduction efficiency using characteristic pollutant-CO2 concentration 

ratios. 

100%

[CO ]

[P]

[CO ]

[P]

CT Efficiency (%) 1-

2 BL

BL

2 CT

CT

×

























= , 

where the “[]” designate concentrations, and CT and BL describe the control technology 

test and baseline runs respectively. In both instances, the background CO2 concentration 

of 402 ppm must be subtracted out so that [CO2] represents the net increase in 

concentration due to engine operation. 

We used this equation to compute the elemental carbon reduction efficiencies for the 

control technologies tested. [Note: We decided to disregard the data from several tests in 

which the ventilation rate was low and leakage from the isolated zone was suspected 

because the absolute concentrations of the CO2 were inconsistent with runs at higher 

ventilation rates. However, the leakage, probably would affect both CO2 and EC (and the 

gases) equally, and a control technology performance estimate could be computed using 
42

the above formula. The remaining issue is that the leak was at the midpoint of the isozone 

with the result that the downstream concentrations would represent different proportions 

of the duty cycle performed upstream and downstream of the leak for different total 

ventilation rates. Thus, we have chosen not to present the results of those test runs in this 

report.] 

Exhaust emission testing 

The isolated zone tests were complimented 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 evaluated in the isolated zone study. The 

measurements were made for the majority of evaluated configurations. This part of the 

study was a joint effort of NIOSH and the Stillwater 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 selected steady-state conditions: 

 

1. torque converter stall (TCS) at intermediate speed, and at full throttle, 

2. high idle (rated speed, no load), and 

3. low idle (idle speed, no load). 

These conditions were assumed to be the only safe and repeatable conditions suitable for 

testing an engine in stationary conditions 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, energy produced by the engine is converted into heat and dissipated in the 

torque converter system. The length of the tests at this mode was limited by the fact that 

the torque converter cooling system is usually not capable of dissipating the generated 

amount of energy for an extended period of time. In order to prevent permanent damage 

of the torque converter the load was taken off the torque converter when the cooling fluid 

exceeded a maximum allowed temperature. Because the TCS condition results in the 

highest engine load and consequently the highest DPM and gaseous emissions of all 

conditions available for testing vehicles in field conditions, it was assumed to be the most 

suitable for such testing 
43

At High idle mode brakes were applied, the transmission was placed in neutral, and the 

engine speed was maintained at rated speed. Typically, DPM emissions were 

substantially lower than those found at TCS conditions. 

At low idle mode brakes were applied, the transmission was placed in neutral, and engine 

speed was maintained at idle speed. Again, DPM emissions typically are substantially 

lower than those on high idle and TCS. 

Equipment, instrumentation, and methods for measurement of 

exhaust pipe emissions 

When aftertreatment systems were tested, samples were collected from sampling ports 

located upstream and downstream of the systems. The effects of the after treatment 

technologies on the emissions were determined by comparing results obtained from the 

sampling ports located upstream and downstream of the systems. In the case of tests 

involving fuel formulations the emissions were obtained at the tailpipe for different cases. 

The effects were determined by comparing results of the similar tests conducted with 

different fuel formulations. 

The inlet side of each of the test DPF systems was equipped with at least two 0.5-in NPT 

ports made with SS pipe couplings that were welded over a 0.5-in (13-mm) to 0.75-in 

(19-mm) hole in the exhaust pipe. 

All NIOSH emissions measurements were repeated at least 3 times for each of the test 

conditions. The test procedures remained uniform across all the engine/vehicle 

configurations. 

NIOSH used the following methods and instrumentation for measurement of DPM and 

gaseous emissions in the exhaust systems of the test vehicles: 

1. An ECOM Model KL portable emissions analyzer from ECOM America, 

Norcross, GA was used to measure O2, CO, NO and NO2.

2. The same portable emissions analyzer was used to sample DPM for 

Bacharach smoke number and to obtain samples on tissue quartz for carbon 

analysis 

Stillwater Nye mine maintenance personnel used their Enerac 400 Micro-Emission 

Monitoring System (EMS) emission monitoring system from Energy Efficiency 

Systems Westbury, New York to measure O2, CO, NO and NO2 following their own 

test protocol of logging data through a single pass throughout the test conditions. 

Both the ECOM Model KL and the Enerac 400 EMS utilized standard electrochemical 

sensors to measure concentrations of O2, CO, NO and NO2. The emissions of CO2 were 

calculated. 
44

Results and Discussion 

Ventilation rates 

NIOSH measured the ventilation rates continuously over the course of each of the tests 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 

Figure 15 through Figure 19. 

0

5000

10000

15000

20000

25000

30000

35000

40000

0 2000 4000 6000 8000 10000 12000

Relative time [sec]

Ventilation rate [cfm]

Baseline (05/26/2003, VRC= 2.76) Engelhard DPX (05/26/2003, VRC=2.71)

Figure 15. Ventilation rates for the tests involving #92128 
45

0

2000

4000

6000

8000

10000

12000

14000

16000

0 2000 4000 6000 8000 10000 12000 14000

Relative time [sec]

Ventilation rate [cfm]

Baseline (05/22/2003, VRC=0.82) CleanAir (05/22/2003, VRC=0.82)

Figure 16. Ventilation rates for the tests involving #92133 

0

10000

20000

30000

40000

50000

60000

70000

0 5000 10000 15000 20000 25000

Relative time [sec]

Ventilation rate [cfm]

Baseline 1(05/23/2003, VRC=4.55) Baseline 2 (05/23/2003, VRC=4.54)

DCL (05/21/2003, VRC=0.31) Donaldson (05/23/2003, VRC=1.19)

Figure 17. Ventilation rates for the tests involving #92506 
46

0

5000

10000

15000

20000

25000

30000

35000

40000

0 1000 2000 3000 4000 5000 6000

Relative time [sec]

Ventilation rate [cfm]

Baseline (5/27/2003, VRC=2.89) Baseline Bio (5/27/2003, VRC=2.92) ECS (5/24/2003, VRC=1.27)

B20 (5/28/2003, VRC=2.84) B50 (5/28/2003, VRC=2.93)

Figure 18. Ventilation rates for the tests involving #92526 

0

10000

20000

30000

40000

50000

60000

70000

0 1000 2000 3000 4000 5000 6000 7000 8000

Relative time [sec]

Ventilation rate [cfm]

Baseline D1 (5/29/2003, VRC=3.41) Baseline D2 (5/30/2003, VRC=3.34) DCL MineX (5/29/2003, VRC=3.35)

Figure 19. Ventilation rates for the tests involving #99942 
47

The average ventilation rates normalized with respect to MSHA approved ventilation 

rates for the tested engines are given in Table 6. 

Table 6. Average ventilation rates normalized with respect to MSHA ventilation 

rates and contribution of the tested vehicles/configurations to concentrations of 

carbon dioxide at downstream sampling station 

Average ventilation rates 

normalized with respect to 

MSHA ventilation rates 

Contribution of the vehicles to 

CO2 concentrations [ppm] 

Test type Date 

High volume 

sampling 

period 

Standard 

sampling 

period 

Maximum Average 

#92128 Haul Truck, MSHA vent 12000 cfm 

Baseline 05/26/03 2.77 2.77 3432 2522 

Engelhard 

DPX 05/26/03 2.71 2.71 3391 2316 

#92133 Haul Truck, MSHA vent rate 12000 cfm 

Baseline 05/22/03 0.82 0.82 1361 1226 

CleanAir 

Systems 05/22/03 0.82 0.82 1487 1337 

#92506 LHD, MSHA vent rate 11500 cfm 

Baseline, #1 

diesel 05/23/03 4.56 4.62 5866 1702 

Baseline, #2 

diesel 05/23/03 4.55 4.61 5472 1799 

DCL BlueSky 05/21/03 0.31 0.31 715 553 

Donaldson 05/23/03 1.19 1.19 1677 1360 

#92526 LHD, MSHA vent rate 10000 cfm 

Baseline 05/27/03 2.89 2.91 7418 3297 

Baseline/ PTX 05/27/03 2.92 2.95 7220 3419 

ECS Cattrap 05/24/03 1.27 1.27 3291 2409 

Biodiesel B20/ 

PTX 05/28/03 2.84 2.87 7048 3424 

Biodiesel B50/ 

PTX 05/28/03 2.93 2.95 7220 3453 

#99942 LHD, MSHA vent rate 15000 cfm 

Baseline, #1 

diesel 05/29/03 3.41 3.46 8338 2447 

Baseline, #2 

diesel 05/30/03 3.34 3.35 8626 2459 

DCL MineX 05/29/03 3.33 3.33 8254 2311 

The isolated zone tests can be divided into two groups with respect to the ventilation rate 

that prevailed during each of the tests. During the first four days of the study (05/21 

through 05/24) the ventilation rates were maintained, generally speaking, below or in the 

neighborhood of MSHA ventilation rates for the particular vehicle (see Figure 16, Figure 

17, Figure 18, and Table 6). The ventilation rates for the rest of the tests were 
48

significantly higher than the MSHA engine nameplate ventilation rates (see Figure 15, 

Figure 17, Figure 18, Figure 19, and Table 6). 

The tailpipe emission measurements showed that none of the tested control technologies 

had a significant effect on the CO2 emissions. This and the fact that CO2 emissions can be 

related to total fuel consumed by diesel engines are the reasons that ambient 

concentrations of CO2 were used to examine the validity of the tests done in the isolated 

zone. The analysis of the results on the contribution of the vehicles to the concentration 

of CO2 in mine air at the downstream sampling station (see Table 6) showed that the tests 

conducted while the ventilation rates were maintained below or in the neighborhood of 

the MSHA ventilation rates had significantly lower CO2 contributions from the vehicles. 

This is evident for the tests involving the DCL Bluesky and the Donaldson filtration 

systems conducted with LHD #92506 in the isolated zone and for the test involving the 

ECS Cattrap DPF system conducted with LHD #92626. The additional evidence of the 

potential problems with the tests conducted while ventilation rates were maintained 

below or in neighborhood of MSHA ventilation rates are the CO2 concentrations 

observed for the baseline cases involving haul trucks #92128 and #92133. The tailpipe 

emissions measurements Table 16 showed that CO2 emissions at high idle, low idle and 

torque converter stall are almost identical for those two trucks that were powered with 

similar model engines (Deutz BF6M1013FC and BF6M1013ECP ). However, the 

contributions of those vehicles to the concentrations of CO2 at the downstream sampling 

station were significantly different. The observed concentrations were two-fold higher for 

#92128 than for #92133 (see Table 6). 

Since a clear explanation for the presented phenomena is not available at this time, the 

authors opted to analyze and discuss only the results of the isolated zone tests that were 

conducted while the ventilation rates were maintained significantly above the MSHA 

ventilation rates. The exception is the two tests conducted with haul truck #92133. Since 

the ventilation rates were almost identical and fairly constant during those two tests 

(Figure 16), the authors believe that those tests are valid and thus included the discussion 

on the effects of the CleanAir Systems DPF system on EC emissions in the report. 
49

The effects of control technologies on elemental carbon 

concentrations 

The results of the elemental carbon analysis on the samples collected using the high 

volume samplers are presented in Table 7 and Table 8. In Table 7, the EC concentrations 

were adjusted to that which would be measured when the engine-appropriate MSHA 

nameplate ventilation rate would prevail. The MSHA vent rate approximates the nominal 

ventilation for normal operating conditions. The data provides the concentration at a 

specific ventilation quantity from which the concentration may be computed for a 

different air quantity. 

The coefficients of variation (CV) for the triplicate samples are also presented in Table 7. 

The CV represents the agreement among the three samples taken in parallel at each of the 

five sampling points. Sample volume, slight spatial differences in actual airborne EC 

concentrations and the analytical error inherent to the NIOSH Method 5040 contribute to 

the CV. The CVs for the elemental carbon results in this study ranged from 1.6 to 10.6 %. 

The CV does not take into account the uncertainty in ventilation measurement. 

The primary reason for measuring airborne elemental carbon was to determine its 

reduction from the use of the control technologies evaluated in this study. Reduction 

computations were made by comparing the concentration of the contaminant of interest 

when operating with and without control technologies, under similar conditions. As 

described earlier in this report (page 38), two different methods were used to normalize 

the data for comparison of control technology to the baseline. The first method used 

ventilation rates to normalize data from different tests (see Equation 4, page39) and the 

results are shown in Table 7. The second method used carbon dioxide concentrations to 

normalize (see Equation 5, page 41) the data and these are presented in Table 8. The CO2

concentrations used for normalization were adjusted for background CO2 concentrations 

of 402 ppm. Note that with one exception, the calculated reduction efficiencies of the 

control technology are nearly identical for both normalization methods. 

As mentioned previously, several of the tests were discarded because of unexplainably 

low CO2 concentrations found at low ventilation rates. However, for the two tests on 

vehicle #92133, although the ventilation rates 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. 
50

Table 7. Elemental carbon results normalized with respect to ventilation rates 

EC 

Test type [μg/m3

] CV [%] 

Reductions 

normalized by vent rate 

[%] 

#92128 Haul Truck, MSHA vent rate 12000 cfm 

Baseline 1182.0 5.3 

Engelhard DPX 51 3.2 96 

#92133 Haul Truck, MSHA vent rate 12000 cfm

Baseline / CDT 1038 10.6 

CleanAir Systems / CDT 15 5.3 99 

#92506 LHD, MSHA vent rate 11500 cfm

Baseline, #1 diesel 938 3.0 

Baseline, #2 diesel 1051 6.6 -12 

#92526 LHD, MSHA vent rate 10000 cfm

Baseline 1328 1.6 

Baseline / PTX 1365 2.0 -3 

Biodiesel B20 / PTX 1015 4.7 26 

Biodiesel B50 / PTX 703 4.3 48 

#99942 LHD, MSHA vent rate 15000 cfm

Baseline, #1 diesel 1112 7.7 

Baseline, #2 diesel 1222 4.0 -10 

DCL MineX 149 2.6 88 

Table 8. Elemental carbon results normalized with respect to CO2 concentrations 

EC CO2 EC/CO2

Test type [μg/m3

] [ppm] [:g/m3/ppm] 

Reductions 

normalized with CO2

[%} 

#92128 Haul Truck, MSHA vent rate 12000 cfm

Baseline 427 878 0.486 

Engelhard DPX 20 855 0.023 95 

#92133 Haul Truck, MSHA vent rate 12000 cfm

Baseline / CDT 1265 1499 0.844 

CleanAir Systems / 

CDT 

18 1618 0.011 99 

#92506 LHD, MSHA vent rate 11500 cfm

Baseline, #1 diesel 206 1126 0.183 

Baseline, #2 diesel 231 1133 0.204 -12 

#92526 LHD, MSHA vent rate 10000 cfm

Baseline 459 1082 0.425 

Baseline / PTX 466 1189 0.392 8 

Biodiesel B20 / 

PTX 

358 1126 0.318 19 

Biodiesel B50 / 

PTX 

240 1133 0.212 46 

#99942 LHD, MSHA vent rate 15000 cfm

Baseline, #1 diesel 326 752 0.433 
51

EC CO2 EC/CO2

Test type [μg/m3

] [ppm] [:g/m3/ppm] 

Reductions 

normalized with CO2

[%} 

Baseline, #2 diesel 366 814 0.450 -4 

DCL MineX 45 745 0.060 87 

The effects of control technologies on concentration of total 

particulate matter (TPM) under 0.8 :m 

This chapter summarizes the results of the total particulate matter (TPM) measurements 

conducted at the upstream and downstream sampling stations using two TEOM 1400a 

ambient particulate monitors. A 10 mm cyclone and impactor was used as a preclassifier 

to eliminate all particles with an average aerodynamic diameter larger than approximately 

0.8 :m. This preclassifier train was identical to those used for the high volume samplers. 

The observed concentrations of TPM measured at the upstream sampling station were 

negligible and therefore they were not used in this analysis. The normalized TPM 

concentrations measured at the downstream monitoring station are presented in Table 9. 

These concentrations are normalized (see Equation 2, page 40) with respect to the MSHA 

ventilation rates specific for each of the engines powering the tested vehicles. 

Table 9. Concentrations of TPM under 0.8 :m the downstream sampling station 

Concentrations of TPM 

[:g/m3] 

Reductions 

[%] 

 

Test Type

Ave. Max. Ave. 

#92128 Haul Truck, MSHA vent rate 12000 cfm 

Baseline 1343.9 1536.3 -- 

Engelhard DPX 341.7 411.6 75% 

#92506 LHD, MSHA vent rate 11500 cfm 

Baseline #1 diesel 3964.1 7313.2 -- 

Baseline #2 diesel N/A N/A -- 

#92526 LHD, MSHA vent rate 10000 cfm 

Baseline 1631.9 2083.0 -- 

Baseline / PTX 1874.6 2324.6 -- 

Biodiesel B20 / PTX 1698.8 2084.8 9% 

Biodiesel B50 / PTX 1416.6 1800.7 24% 

#99942 LHD, MSHA vent rate 15000 cfm 

Baseline #1 diesel 1433.6 2140.2 -- 

Baseline #2 diesel 1735.1 2739.2 -21% 

DCL MineX 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 normalized average values, Equation 

4, page 39. These results show that both the Engelhard and DCL MineX DPF systems 

reduced the TPM in the mine air by approximately 75%. These reductions were lower 
52

than those shown in Table 7 for EC collected on the high-volume samples (88% - 96%). 

However, the difference can be attributed to the fact that the TEOM measures total 

particulate mass gravimetrically while carbon analysis accounts only for the elemental 

carbon fraction of total particulate mass. It can be speculated that particulate matter in the 

treated exhaust contains higher fractions of sulfates, bounded water, and organic carbons 

than untreated exhaust. These aerosols that are transparent to the carbon analysis can 

contribute significantly to the total mass of PM measured by the TEOM. The TEOM 

results also showed that biodiesel blends have the potential to reduce the concentrations 

of TPM in mine air. However, as with the results from the DPF tests, the TEOM results 

showed a lower percent efficiency than that measured using the EC method. 

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 plot 

are due in part to the variation in vehicle duty cycle 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 data proved extremely useful 

as they allowed estimates of the mass of DPM collected on the filters, used for carbon 

analysis, at any given time during the tests. These estimates were used to determine the 

necessary lengths of the high-volume and the standard sampling periods. 

0

500

1000

1500

2000

2500

0 1000 2000 3000 4000 5000 6000 7000 8000

elapsed time [s]

concentration [ug/m^3]

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

LHD #99942 (5/29/03) 
53

The effects of control technologies on count and size 

distribution of particles 

This chapter summarizes the results of the measurements of size distributions and 

concentrations of aerosols at the downstream sampling station accomplished using a 

scanning mobility particle sizer (TSI Inc., St. Paul, Minnesota, Model 3936). Only the 

results of the measurements made while vehicles were performing their duties at the 

downstream loading/dumping point in the isolated zone are presented in this report. 

The results are presented in Table 10 and Figure 21 though Figure 26. The 

statistical parameters and plots for two or three typical measurements are also shown for 

each of the test cases. The geometric means and geometric standard deviations are 

supplied for each of those distributions. The average geometric means and average total 

particulate concentrations are calculated for each set of data. The average total aerosol 

concentrations measured at the prevailing ventilation rates are normalized with respect to 

the MSHA ventilation rates specific for each of the tested vehicles. The effects of the 

tested control technologies on the total number of particles in the mine air are expressed 

as the percentage of change in total particulate count in the mine air with respect to the 

selected baselines. For the majority of the cases the tests where vehicles were operated 

with mufflers and standard fuel were considered to be the baseline cases. The exceptions 

were the tests that were conducted with the objective of assessing the effects of the 

biodiesel blends. In these cases, the test conducted with the LHD #92526 equipped with a 

diesel oxidation catalytic converter (Engelhard Corporation, Iselin, New Jersey, Model 

PTX ) and muffler was considered to be the baseline. 

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

Vehicle 

MSHA 

Vent. 

Rate (VR) 

[cfm] 

Test Type Date Vehicle 

Operator 

Geo. 

Mean 

[nm] 

Geo. 

Std. Dev. 

Average 

Geometric 

Mean [nm] 

Average 

Total 

Particle 

Conc. @ 

MSHA 

VR 

[#/cm3] 

Change 

in Total 

Particle 

Conc. 

[%] 

71.64 1.83 

65.84 1.83 Baseline 

(muffler) 05/26/03 Jim 

64.35 1.90 

67.28 2.88E+08 N/A 

45.14 1.44 

43.46 1.47 

#92128 12000 

Engelhard 

DPX 05/26/03 Jim 

42.63 1.44 

43.74 5.17E+08 79.6 

Baseline 83.75 1.63 

#1 /#2 

diesel 

(muffler) 

05/23/03 Chad 

72.61 1.68 

78.18 9.14E+08 

81.34 1.66 

82.02 1.66 

#92506 11500 Baseline 

#1 /#2 

diesel 

(muffler) 

05/23/03 Chad 

76.39 1.80 

79.91 8.23E+08 -9.9 

#92526 10000 Baseline 85.05 1.68 

(muffler) 05/27/03 Chad 

86.43 1.67 

85.74 6.82E+07 N/A 
54

Vehicle 

MSHA 

Vent. 

Rate (VR) 

[cfm] 

Test Type Date Vehicle 

Operator 

Geo. 

Mean 

[nm] 

Geo. 

Std. Dev. 

Average 

Geometric 

Mean [nm] 

Average 

Total 

Particle 

Conc. @ 

MSHA 

VR 

[#/cm3] 

Change 

in Total 

Particle 

Conc. 

[%] 

Baseline 72.22 1.75 

(PTX and 

Muffler) 

05/27/03 Chad 

72.59 1.74 

72.40 7.32E+07 7.4 

Biodiesel 65.83 1.66 

B20 (PTX) 05/28/03 Chad 

66.01 1.65 

65.92 9.72E+07 32.7 

63.32 1.60 

 

Biodiesel 

B50 (PTX) 05/28/03 Chad 

60.21 1.61 

61.76 9.11E+07 24.4 

74.41 1.64 

76.60 1.65 

Baseline 

#1 diesel 

(muffler) 

05/29/03 John 

75.24 1.65 

75.42 3.97E+07 N/A 

81.57 1.65 

81.68 1.63 

Baseline 

#2 diesel 

(muffler) 

05/30/03 John 

82.53 1.63 

81.93 4.85E+07 22.2 

40.70 1.58 

35.49 1.57 

#99942 15000 

DCL 

MineX 05/29/03 John 

37.99 1.59 

38.06 7.09E+07 78.7 

The carbon analysis and TEOM measurements showed that dramatic reductions in mass 

concentrations of elemental carbon and particulate matter in mine air were achieved with 

the tested diesel particulate filters. Since both tested DPFs, Engelhard DPX and DCL 

MineX, offered dramatic reductions in the number of larger particles, it can be concluded 

that the size selective measurements qualitatively agree with those results (see Figure 21 

and Figure 22). The size distributions of the particles that are observed for the tests with 

filtered exhaust are characterized with significantly lower geometric means and higher 

peak concentrations than the size distributions observed during the tests with unfiltered 

engines/vehicles. The distributions of particles generated by vehicles equipped with a 

muffler were characterized by geometric means (GM) ranging from 64 to 87 nm. In 

contrast, the distributions of particles generated by vehicles equipped with diesel 

particulate filters were characterized by a GM ranging from 35 to 45 nm (see Table 10). 

Additionally, a significant increase in the number of the particles, approximately 80 

percent, was evident for both cases when mufflers were replaced with DPFs (see Table 

10). Since carbon analysis shows very low mass concentrations of the elemental carbon 

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, 

chemical analysis of the DPM samples is not available to confirm this hypothesis. 

It is important to note that the distributions and concentrations of aerosols in the observed 

size range are highly dependant 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 
55

at the downstream sampling station. The average relative humidity measured at the 

downstream station during the tests was approximately 90 %. 

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]

Engelhard #1 Engelhard #2 Engelhard #3 Muffler #1 Muffler #2 Muffler #3

Figure 21. Size distribution of aerosols in mine air for truck #92128 - Engelhard 

DPX DPF vs. Muffler 
56

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]

DCL MineX #1 DCL MineX #2 DCL MineX #3 Muffler #1 Muffler #2 Muffler #3

Figure 22. Size distribution of aerosols in mine air for LHD #99942 - DCL MineX 

vs. Muffler 

Due to an unfortunate mistake in supplying fuel for a number of the tests, including those 

conducted with LHD #92506 (see chapter on fuel), the two tests that were designed to 

show the effects of the fuel formulation (#1 vs. #2 diesel) on the emissions were actually 

two tests conducted under very similar conditions. Since both tests were conducted with 

approximately a 90% #2 and 10% #1 diesel blend supplied to the engine, these tests were 

seen as an opportunity to examine repeatability of the applied test methodology. The 

results of the size selective measurements shown in Figure 23 agree with the other 

measurements used in this study, showing relatively good inter-test agreement. 
57

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]

Fuel 1 #1 Fuel 1 #2 Fuel 2 #1 Fuel 2 #2 Fuel 2 #3

Figure 23. Size distribution of aerosols in mine air for truck #92506 equipped with 

muffler - Fuel 1 vs. Fuel 2 

The effects of the diesel oxidation catalytic converter (Engelhard PTX) 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 somewhat lower 

geometric means (72.40 vs. 85.74 nm) and higher peak concentrations (1.75*107

 vs. 

1.50*107

 #/cm3) than the size distributions observed during tests with the muffler alone 

(see Table 10 and Figure 24). Approximately a 7 percent increase in the number of the 

particles was found when the muffler was replaced with a DOC/muffler combination (see 

Table 10). 
58

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]

Engelhard PTX #1 Engelhard PTX #2 Muffler #1 Muffler #2

Figure 24. Size distribution of aerosols in mine air for LHD #92526 - Engelhard 

PTX/Muffler vs. Muffler 

Figure 25 illustrates the effects of blending biodiesel with #2 diesel on the size 

distribution of aerosols in the mine air. The results indicate that the size distributions of 

the particles for the cases when these particular biodiesel blends were used were 

characterized with somewhat lower geometric means 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 blend (50% biodiesel and 50% #2 diesel, GM 

= 61.76 nm) and B20 blend (20% biodiesel and 80% #2 diesel, GM = 65.92 nm) indicate 

that increasing the biodiesel fraction of a blend might result in decreasing the geometric 

means for the size distributions. In addition, a significant increase in the number of 

particles was found when a biodiesel blend was supplied to the engine (see Table 10). 

These results do not indicate a potential trend in the relationship between the biodiesel 

fraction in a blend and total number of particles emitted. 
59

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]

Diesel #1 Diesel #2 Biodiesel B20 #1 Biodiesel B20 #2 Biodiesel B50 #1 Biodiesel B50 #2

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

DOC (Engelhard PTX) and muffler - #2 diesel vs. Biodiesel B20 vs. Biodiesel B50 

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 geometric means (81.93 vs. 75.42 nm) 

and higher peak concentrations (3.16*107

 vs. 3.01*107 #/cm3) than the size distributions 

observed for the tests with #1 diesel (see Table 10 and Figure 26). Approximately a 22 % 

increase in the number of the particles was found when #2 instead of #1 diesel was fueled 

to the engine (see Table 10). This finding is corroborated by the TEOM results, which 

also showed an increase in the mass concentration in mine air exceeding 20% when #2 

instead of #1diesel was fueled to the engine. 
60

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]

Diesel D1 #1 Diesel D1 #2 Diesel D1 #3 Diesel D2 #1 Diesel D2 #2 Diesel D2 #3

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

muffler - #1 diesel vs. #2 diesel 
61

The effects of control technologies on ambient concentrations 

of carbon monoxide (CO), carbon dioxide (CO2), nitric oxide 

(NO), and nitrogen dioxide (NO2) 

The normalized average and maximum concentrations of carbon monoxide (CO), carbon 

dioxide (CO2), nitric oxide (NO), and nitrogen dioxide (NO2) measured at the 

downstream sampling station are shown in Table 11. The concentrations of CO2 were 

measured using INNOVA 1312 and concentrations of CO, NO, and NO2 were measured 

by iTX multi-gas monitors. The obtained concentrations were normalized with respect to 

the MSHA ventilation rates specific for each of the engines powering the tested vehicles 

(Equation 2, page 39). The observed background concentrations of CO, NO, and NO2 at 

the upstream sampling station were negligible and therefore there was no need to use 

them 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 ACGIH time weighted 

average (TWA) threshold limit values (TLVs) adopted by MSHA for the underground 

metal/nonmetal mining regulations (30 CFR Part 57.5001). 

Table 11. Normalized concentrations of carbon monoxide (CO), carbon dioxide 

(CO2), nitric oxide (NO), and nitrogen dioxide (NO2) at downstream sampling 

station 

Test Type CO [ppm] CO2 [ppm] NO [ppm] NO2 [ppm] 

Max. Ave. Max. Ave. Max. Ave. Max. Ave. 

#92128 Haul Truck, MSHA vent 12000 cfm

Baseline 11.1 6.7 3834 2924.2 22.2 17.0 1.1 0.6 

Engelhard DPX 0.0 0.0 3793 2718.1 16.2 5.0 4.9 1.3 

#92133 Haul Truck, MSHA vent 12000 cfm*

Baseline 3.3 2.6 2208 1229 7.4 6.0 0.4 0.2 

Clean Air + CDT 0.0 0.0 2384 1327 7.4 6.6 1.0 0.7 

#92506 LHD, MSHA vent rate 11500

Baseline, #1 23.1 3.3 6268 2104.4 23.1 7.2 2.3 1.3 

Baseline, #2 23.0 4.3 5874 2201.1 23.0 6.8 2.3 1.2 

#92526 LHD, MSHA vent rate 10000 

Baseline 23.3 6.0 7820 3699.4 43.7 19.4 3.5 1.5 

Baseline + PTX 0.0 0.0 7622 3821.4 50.1 22.5 4.4 1.8 

Biodiesel 

B20+PTX 

0.0 0.0 7450 3825.5 45.9 21.2 4.0 1.7 

Biodiesel 

B50+PTX 

0.0 0.0 7622 3855.3 53.1 23.5 4.7 1.9 

#99942 LHD, MSHA vent rate 15000 

Baseline, #1 31.2 4.9 8740 2848.8 48.5 16.6 3.5 0.9 

Baseline, #2 26.8 4.5 9028 2861.2 46.8 16.7 3.0 0.8 

DCL MineX 0 0.0 8656 2712.8 40.0 12.1 5.7 2.1 

* The absolute values of the data for this vehicle is questionable, e.g., CO2 is low compared to other 

vehicles; however, the relative changes between baseline and DPF test are quite possibly valid. 
62

Carbon monoxide (CO) 

The average and maximum normalized concentrations of CO, shown in Table 11, are 

significantly below the TWA TLV for CO of 50 ppm. The concentrations of CO were 

found to be practically undetectable for cases when the catalyzed diesel particulate filters 

from Engelhard and DCL, and the diesel oxidation catalytic converter from Engelhard 

(see Table 11) were fitted to the tested vehicles. Even in the cases 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. 

Carbon dioxide (CO2) 

The average and maximum concentrations of CO2 observed for the tests conducted 

during the study are shown in Table 11, Figure 27, Figure 28, and Figure 29. Both 

average and maximum CO2 concentrations at the downstream station were below the 

TWA TLV for CO2 (5000 ppm) 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, Figure 27, Figure 28, and Figure 29). 

The concentrations of CO2 were found to be unaffected by the tested diesel particulate 

filters from Engelhard and DCL, and the diesel oxidation catalytic converter from 

Engelhard (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. 
63

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

Relative time [sec]

Concentrations [ppm]

Baseline D1/D2 (05/23/2003) Baseline D1/D2 (05/23/2003)

Figure 27. Normalized CO2 concentrations for the tests with LHD #92506 
64

0.0

1000.0

2000.0

3000.0

4000.0

5000.0

6000.0

7000.0

8000.0

9000.0

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

Relative time [sec]

Concentrations [ppm]

Baseline (05/27/2003) Engelhard PTX (05/27/2003) B20 (05/28/2003) B50 (05/28/2003)

Figure 28. Normalized CO2 concentrations for tests the 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

Relative time [sec]

Concentrations [ppm]

Baseline D1 (05/29/2003) Baseline D2 (05/30/2003) DCL MineX (05/29/2003)

Figure 29. Normalized CO2 concentrations for the tests with LHD #99942 
65

Nitric oxide (NO) 

The average normalized concentrations of NO shown in Table 11 were found to be 

somewhat lower than the TWA TLV 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 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

Relative time [sec]

Concentrations [ppm]

Baseline (5/27/2003) Engelhard PTX (5/27/2003) B20 / PTX (5/28/2003) B50 / PTX (5/28/2003)

Figure 30. Normalized NO concentrations for the tests with LHD #92526 
66

0.0

10.0

20.0

30.0

40.0

50.0

60.0

0 1000 2000 3000 4000 5000 6000 7000 8000

Relative time [sec]

Concentrations [ppm]

Baseline D1 (5/29/2003) Baseline D2 (5/29/2003) DCL MineX (5/29/2003)

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 wash-coated 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, presented in Table 11, show that the 

average normalized concentrations of NO2 increased approximately two times (1.3 vs. 0.6 

ppm) when haul truck #92128 was equipped with Engelhard DPX DPF system instead of 

a muffler. Comparable increases (2.1 vs. 0.9 ppm) in NO2 concentration was observed 

for the DCL MineX DPF system and also for the CleanAir system (0.7 vs. 0.2 ppm) (see 

Table 11). It is important to note that if the required MSHA ventilation rates were 

maintained during the tests, the average concentration of NO2 over the test periods would 

not have exceeded 3 ppm, the long term exposure limit for NO2. It is also important to 

note that during the test involving #99942 equipped with DCL MineX, the MSHA 

ventilation rate normalized peak concentrations exceeded 5 ppm, the short term exposure 

limit (STEL) for NO2 , on several occasions (see Figure 33). An analysis of the data 

showed that the average and peak concentrations of NO2 were only slightly higher in the 

cases 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 DOC was fitted 

to the vehicle. 
67

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 2000 4000 6000 8000 10000 12000

Relative time [sec]

Concentrations [ppm]

Baseline (05/26/2003) Engelhard DPX (05/26/2003)

Figure 32. Normalized NO2 concentrations 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

Relative time [sec]

Concentrations [ppm]

Baseline D1 (5/29/2003) Baseline D2 (5/29/2003) DCL MineX (5/29/2003)

Figure 33. Normalized NO2 concentrations for the tests with LHD #99942 
68

It is important to note that the discussion presented in this section is based on the 

measurements conducted 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 monitors at the sampling stations established on the tested vehicles. Since 

those sampling stations on the vehicles were located relatively close to the operators, 

these results can be used to estimate the exposure of the operators to the gases and 

particulate matter. The concentrations of the measured gases at the downstream and 

vehicle stations were found to be comparable, and, in a majority of the cases, slightly 

higher peaks were observed by the instrument used at the vehicle sampling stations (see 

Figure 34). This indicates 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

Relative time [sec]

Concentrations [ppm]

Baseline D1 Downstream (5/29/2003) Baseline D1 Vehicle (5/30/2003) Baseline D2 Downstream (5/29/2003)

Baseline D2 Vehicle (5/29/2003) DCL MineX Downstream (5/29/2003) DCL MineX Vehicle (5/29/2003)

Figure 34. Normalized NO2 concentrations at downstream and vehicle sampling 

stations for the tests with LHD #99942 
69

Analysis of exhaust temperature and back pressure data 

A 4-channel Logic Beach MiniLogger was used to record 10-second average exhaust 

backpressure, exhaust gas temperature and a surface temperature. It was also used to 

record the analog output of the Max fuel flow metering system when that device was 

installed on the Caterpillar engines and working. Because fuel was used for engine 

cooling, the fuel flow rate for Deutz engines was beyond the range of the Max fuel flow 

metering system. 

We examined the exhaust temperatures for all test runs and determined the 70th percentile 

temperature (the temperature that the exhaust temperature was below 70% of the time, or 

T30 the temperature exceeded 30% of the time.) for each run. The temperatures below 

130 °C were excluded from considerations. T30 is considered as a benchmark for 

matching various DPF passive regeneration schemes to exhaust temperatures. T30 was 

determined by using the NIOSH spreadsheet referenced in the NIOSH-MSHA DPF 

selection guide accessible from the NIOSH Mining Toolbox on the WEB. 

We examined the exhaust backpressures when diesel particulate filters (DPFs) were used. 

We were looking for decreases in back pressure while the exhaust temperatures were 

high, or a general decreasing trend in backpressure throughout the test run. Either of these 

signs would indicate that the exhaust temperature was sufficient to burn off some of the 

DPM/soot collected by the DPF. 

In some instances the temperature data from one or both channels appeared erratic. A 

post test check of the data logger and sensor performance at PRL confirmed that it was 

still accurate. However, there may have been some interference on the data from the 

connection to the Max fuel flow metering system. 

Table 12 shows the results of the analysis of the vehicle exhaust logs. 

Table 12. Results of the on-board temperature and exhaust backpressure logs 

T30 Temperature Backpressure 

Test Type [°C] 

Ranges 

min-max:start 

min-max:end 

DPF 

Regenerates? 

#92128 Haul Truck 

Baseline 260.0 2 to 15 

Engelhard DPX 265 35 to 100 No

#92133 Haul Truck 

Baseline (+ CDT) 410 NA 

Clean Air + CDT 440 16-62; 2.5-9 Yes

#92506 LHD 

Baseline, #1 diesel 455 NA 

Baseline, #2 diesel 455 NA 
70

T30 Temperature Backpressure 

Test Type [°C] 

Ranges 

min-max:start 

min-max:end 

DPF 

Regenerates? 

DCL BlueSky 490 12-28; 35-80 No

Donaldson 370 .25 to 2.3 NA

#92526 LHD 

Baseline 460 2 to 11 

Baseline + PTX 440 4.5 to 11.5 

ECS CATTRAP 240 10 to 33 No

Biodiesel B20+PTX 440 6 to 11.5 NA

Biodiesel B50+PTX Faulted 5 to 11.5 NA

#99942 LHD 

Baseline, #1 diesel Faulted faulted 

Baseline, #2 diesel 500 12 to 25 

DCL MINEX Faulted faulted ?

Vehicle #92128 

Baseline for Engelhard

Exhaust temperatures over the sampling run were quite low with T30 at about 260° C; the 

data appeared erratic. The other temperature channel exhibited the same erratic behavior. 

The exhaust backpressure is not relevant but varied between 2 and 15 inches water gage 

(WG). 

Engelhard DPX, aged Platinum Catalyzed DPF

Exhaust temperature logs appear peculiar: one channel ranges from about 22 to 460 °C 

with a high frequency component whereas the other channel is a moderated temperature 

with smoother behavior. The former was chosen as the exhaust gas temperature. Both 

were analyzed: The T30 for the exhaust temperature was only 300° C whereas the T30 for 

the surface temperature was about 260° C. Based on the exhaust temperature, the 

Engelhard DPF should not regenerate. The backpressure ranges from about 35 to 100 

inches WG and shows a bimodal distribution at the lower and upper ranges. 

Backpressures were excessive. They did not decrease over the test run, and DPF 

regeneration is not evidenced. 

Vehicle #92133 

Baseline for CleanAir Systems

Temperature analysis showed T30 of 410° C, compared to 430° C when the DPF was 

installed. 
71

CleanAir Systems with CDT fuel additive

BP varied from 15 to 60 in WG at the start of the run and decreased to 2 to 10 in WG at 

the end of the 3 hour and 22 minute test run. The graph of BP and exhaust temperature, 

Figure 35, presents a striking example of DPF regeneration. T30 over the test run 

computed to be 440° C. Although the CleanAir DPF system regenerated during testing, 

the fact that it arrived loaded from production indicates that it may not be regenerating 

during actual production cycles. The history of the system just prior to testing is not 

currently known. 

Figure 36 shows the graphical results of the temperature frequency analysis performed by 

the spreadsheet mentioned earlier. The intersection of the 30% horizontal with the 1 

minus the cumulative frequency line shows the T30 temperature at 440° C. 

Vehicle T & BP log

Clean Air + CDT

Exhaust Temp, 'C

BP, in. WG

0

100

200

300

400

500

600

08:38:24 09:50:24 11:02:24 12:14:24 13:26:24 14:38:24

Local Time

Exhaust Temp, 'C

0

10

20

30

40

50

60

70

BP, in. WG

Exhaust Temp, 'C BP, in. WG

Figure 35. Vehicle exhaust temperature and backpressure log during the isozone 

test run
72

Temperature Histogram

10-degree C increments

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%

130140150160170180190200210220230240250260270280290300310320330340350360370380390400410420430440450460470480490500

Temperature, deg C

Percent

0

20

40

60

80

100

120

140

160

180

200

Count 

Count=Num of times exhaust is within T 10-deg "bins" Percent of time that exhaust is greater than T

Figure 36. Temperature frequency distribution and “more than” type cumulative 

frequency distribution used to determine T30

Tailpipe emissions testing

The vehicle logger was recording during the emissions testing in the shop. Close 

examination of the temperature and backpressure traces reveal the occurrence of 

regeneration. This is shown in Figure 37 in a box around the area of interest. The top 

trace representing exhaust temperature rises slowly, whereas the lower trace representing 

backpressure rises then falls rapidly before plunging even lower. The latter precipitous 

fall represents the engine going to idle, whereas the preceding decrease as exhaust 

temperature rises indicates soot removal. 
73

Vehicle T & BP log

Clean Air + CDT

Exhaust Temp, 'C

BP, in. WG

0

50

100

150

200

250

300

350

400

450

500

14:09:36 14:16:48 14:24:00 14:31:12 14:38:24 14:45:36 14:52:48 15:00:00

Local Time

Exhaust Temp, 'C

0

10

20

30

40

50

60

BP, in. WG

Exhaust Temp, 'C BP, in. WG

Figure 37. Exhaust T and BP during emissions testing showing DPF regeneration

Vehicle #92506

Baseline #1 diesel and baseline #2 diesel

T30 for both runs was between 450° C and 460° C. 

Donaldson disposable high temperature filter

This filter was not supposed to regenerate and did not. 

Backpressure range was constant over the length of the test, which was too short 

considering that the filter was clean and new and clean filters do not filter as well as 

when they are partially loaded. The BP range was nominally <0.5 to 2.25 inches WG. 

T30 for the run time in isolated zone (longer than the time needed to collect sample), 

which included warm-ups but no idle time, was about 370° C. This can be compared to 

the T30 of 490 °C for the same vehicle during the DCL BlueSky run. The location of the 

temperature sensor may have been different since different exhaust system configurations 

were used. 
74

DCL Blue Sky DPF

Backpressures ranged from 12 to 28 inches at the start of the test (range results from 

engine load and speed) to 35 to 80 inches WG at the end of the test. T30 was 490 °C. This 

DPF did not regenerate and was not supposed to by design, although it does have a 

platinum catalyst. 

Vehicle #92526

Baseline

Baseline with PTX oxidation catalyst

Baseline with PTX and B20 Biodiesel blend

Baseline with PTX and B50 Biodiesel blend

The backpressure and temperature data from these four runs are similar. Note that the 

PTX may have introduced some exhaust back pressure. T30 was about 440 °C for all 

cases; however there is concern from the look of the temperature data that the 

temperature logging may have been faulty for the B50 run. 

ECS Cattrap with DOC

T30 was 340 °C. There was no evidence of regeneration. T30 required for the base metal 

catalyst for regeneration is about 400 to 420 °C. 

Vehicle #99942

Baseline on #1 and #2 diesel fuel

DCL MineX

We failed to get a reliable temperature log for the #1 diesel run; T30 for the run on #2 

diesel fuel showed a T30 of 500 °C. This temperature was much higher than for Vehicle 

#92526 whose engine was also a 3306 DITA but was derated. This relation was expected. 

The back pressure for the #2 run registered between 12 and 25 in WG but there was no 

restriction other than a muffler, so the data must be in error. All other back pressure and 

temperature data were deemed faulty. 
75

Results of the Tailpipe Emissions Measurements 

Particulate matter emissions, Elemental Carbon 

The elemental carbon results from the tailpipe measurements are summarized in this 

chapter. The results of the analysis and calculated reductions observed for the tested 

control technologies are presented in Table 13. 

Table 13 : Effects of control technologies on elemental carbon emissions 

EC [:g/m3] 

HI 

EC [:g/m3] 

TCS 

Reduction of EC 

[%] Test Type

Up stream Down 

stream Up stream Down stream HI TCS 

#92128 Haul Truck 

Engelhard DPX 2369 < 920 18230 < 920 > 61 > 95

#92133 Haul Truck 

Clean Air 6043 < 920 33537 < 920 > 85 > 97

#92506 LHD 

DCL BlueSky 5282 1055 23316 < 920 80 > 96

Donaldson 3353 < 920 18230 1748 > 72 90

#92526 LHD 

ECS Cattrap 8898 < 920 8254 < 920 > 90 > 89

Baseline, PTX 16049 11529 8230 6712 28 18

Biodiesel B20, PTX 13798 12532 5641 4858 14 31

Biodiesel B50, PTX 9890 8690 4537 4217 38 45

#99942 LHD 

DCL MineX 40838 < 920 16417 < 920 > 98 > 94

The NIOSH 5040 method has a limit of quantification (LOQ) of approximately 1.5 

μg/filter. This LOQ was converted into an equivalent concentration for the exhaust 

volume sampled. If the EC sample taken after the control technology was below the 

LOQ, the downstream concentration was assigned the LOQ equivalent concentration and 

used to compute the EC reduction efficiency of the aftertreatment technology. This 

procedure resulted in a conservative estimate of the control efficiency. For most of the 

high idle mode tests, the EC was below the LOQ, and the baseline was so low that it was 

not possible to calculate a reduction with confidence. The results of the analysis on the 

samples collected at TCS mode show that the tested DPF systems were over 90 % 

efficient in removal of elemental carbon (see Table 13 and Figure 38). Figure 38 presents 

the reduction of EC emissions for TCS mode. The yellow bars show the reductions 

calculated with actual results while red bars show the minimum reductions that were 

calculated using LOQ values instead of the actual results that were below LOQ. 
76

0.00

20.00

40.00

60.00

80.00

100.00

120.00

Biodiesel B20,PTX

Biodiesel B50,PTX

Donaldson

ECS CATTRAP

DCL MINEX

Engelhard DPX

DCL BlueSky

Clean Air

type of control tech

Reduction (%)

Figure 38: Reduction of EC emissions at TCS mode 

It is interesting to note that the Engelhard PTX DOC reduced the EC emissions by 18 % 

at the TCS and 28 % at HI, although the PTX DOC was only expected to affect the OC 

part of DPM. 

Particulate matter emissions, Bacharach Smoke Numbers 

 

This section summarizes the results of the Bacharach Smoke number tests collected 

during tailpipe emission measurements. In this study the Bacharach Smoke number was 

used as a qualitative measure to estimate the effectiveness of the DPF’s tested. This was 

accomplished by pulling a sample both upstream and downstream of the DPFs. The 

Bacharach smoke number methodology was discussed in detail earlier in this report, page 

42. Typically when a DPF is working effectively, the smoke number should be zero. 

Upstream values for the smoke number can range anywhere from 3 to 10. The results 

from the smoke number tests are presented in Table 1. For each of the DPFs tested, the 

Bacharach smoke numbers for upstream samples ranged from 3 to 9 while all the samples 

downstream of the DPFs measured zero. These data indicate that this method can be used 

to estimate the efficacy of DPFs, and further signify that the DPF’s tested in this study 

were working effectively. 
77

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 

Clean Air 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 MineX 9.0 0.0 8.0 0.0 

The results indicate significant reductions of DPM concentrations in the exhaust by tested 

DPF systems (Engelhard DPX, CleanAir Systems, and DCL MineX). The Bacharach 

smoke numbers obtained upstream and downstream of the tested DOC showed 

insignificant reductions in DPM by DOC (Engelhard PTX). 

The Bacharach smoke numbers presented in Table 14 do not show significant reductions 

of DPM concentrations in the exhaust for biodiesel blends. The numbers presented were 

sampled upstream and downstream of the diesel oxidation catalyst and no difference is 

apparent between the upstream and downstream samples. The qualitative nature of this 

methodology makes it less effective at measuring small decreases in DPM. 

Emissions of carbon monoxide, carbon dioxide, nitric oxide, and 

nitrogen dioxide 

The effects of tested control technologies on emissions of CO, CO2, NO, and NO2 were 

estimated on a basis of the measurements made upstream and downstream of tested 

control technologies. The gases were measured for three operating conditions, LI, HI, and 

TCS, using ECOM KL (NIOSH) and ENERAC 400 EMS (Stillwater). 

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 

#92526 fueled with the biodiesel blend to the results upstream of the ECS Cattrap when 

the #92526 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 #92526 fueled with biodiesel blends. 

The agreement between ECOM KL and ENEARAC 400 EMS was found to be within the 

experimental error. The discrepancies in some of the readings can be explained by 

differences in the protocols used by the instruments. 
78

The results of the CO concentration measurements are given in Table 15. The catalyzed 

DPF systems and DOC tested in this study reduced drastically the concentrations of CO. 

The Donaldson disposable filter also surprisingly reduced CO emissions. The extremely 

high concentrations of CO in the exhaust of the LHD #92506 at HI conditions indicate 

serious problems with the engine fueling system. The CO emissions from the other 

vehicles were within the manufacturers specifications. 

Table 15. CO concentrations 

CO [ppm] 

HI 

CO [ppm] 

LI 

CO [ppm] 

TCS Test Type Upstream 

Down 

stream 

Upstream Down 

stream 

Upstream Down 

stream 

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 2437.0 1329.0 168.0 3.0 386.0 3.0 ECOM 

2207.0 910.0 208.0 0.0 460.0 0.0 Enerac 

Donaldson N/A N/A N/A N/A N/A N/A ECOM 

2960.0 1359.0 248.0 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 MineX 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 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. 

Table 16. CO2 concentrations 

CO2 [%] 

HI 

CO2 [%] 

LI 

CO2 [%] 

TCS Test Type Upstream 

Down 

stream 

Upstream Down 

stream 

Upstream Down 

stream 

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
79

CO2 [%] 

HI 

CO2 [%] 

LI 

CO2 [%] 

TCS Test Type Upstream 

Down 

stream 

Upstream Down 

stream 

Upstream Down 

stream 

Instrument

#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 MineX 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 and Figure 

39. The CleanAir Systems DPF system did not significantly affect NO emissions. The 

NO emissions were significantly affected by the other tested systems. They were 

significantly lower for the Engelhard DPX , the ECS Cattrap, and the DCL MineX for all 

test modes. In the case of the DCL BlueSky and the Donaldson filtration systems the 

effects on the NO emissions were found to be strongly dependent on the engine operating 

conditions. The effects of biodiesel blends could be characterized as marginal. 

Table 17. NO concentrations 

NO [ppm] 

HI 

NO [ppm] 

LI 

NO [ppm] 

TCS Test Type Upstream 

Down 

stream 

Upstream Down 

stream 

Upstream Down 

stream 

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
80

NO [ppm] 

HI 

NO [ppm] 

LI 

NO [ppm] 

TCS Test Type Upstream 

Down 

stream 

Upstream Down 

stream 

Upstream Down 

stream 

Instrument

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 MineX 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

0.0

100.0

200.0

300.0

400.0

500.0

600.0

700.0

Engelhard DPX

Clean Air

DCL BlueSky

Donaldson

ECS CATTRAP

Biodiesel B20,PTX

Biodiesel B50,PTX

DCL MINEX

NO (ppm)

upstream downstream

Figure 39. NO Emissions in TCS mode 

 

The results of the NO2 emission measurements are summarized in Table 18 and Figure 

40. Significantly higher NO2 concentrations were observed downstream than upstream of 

the platinum coated filters tested in this study (Engelhard DPX and DCL MineX). Four 

fold increases in NO2 emissions were observed at TCS conditions. The significant 

increases in NO2 emissions were also observed for ECS Cattrap system that had an ECS 

DOC installed on its outlet. That system increased NO2 emissions almost six fold at TCS 

conditions. The ECS DOC was new and was installed with the DPF. The NO2

concentrations need to be closely monitored in the underground work areas where 

vehicles equipped with these filters, that have high potential of converting NO to NO2, are 

used. 

The results of these measurements show no significant increase in NO2 emissions when 

biodiesel blends B20 (20% biodiesel, 80% #2 diesel) and B50 (50% each biodiesel and 

#2 diesel) were used instead of #1 diesel. 
81

Table 18: NO2 concentrations 

NO2 [ppm] 

HI 

NO2 [ppm] 

LI 

NO2 [ppm] 

TCS Test Type Upstream 

Down 

stream 

Upstream Down 

stream 

Upstream Down 

stream 

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, PTX 22.0 16.0 34.0 36.0 16.0 36.0 ECOM

215.0 213.0 257.0 251.0 501.0 509.0 Enerac

Biodiesel B50, PTX 21.0 21.0 18.0 - 12.0 40.0 ECOM

6.0 3.0 43.0 41.0 6.0 8.0 Enerac

#99942 LHD 

DCL MineX 28.3 68.0 - - 17.5 89.5 ECOM

10.0 85.0 29.0 190.0 10.0 45.0 Enerac
82

0.0

100.0

200.0

300.0

400.0

500.0

600.0

Engelhard DPX

Clean Air

DCL BlueSky

Donaldson

ECS CATTRAP

Biodiesel B20,PTX

Biodiesel B50,PTX

DCL MINEX

NO2 (ppm)

upstream downstream

Figure 40. NO2 Emissions in TCS mode 

Implementation of the DPF Systems 

The costs of the DPF systems and their installations are summarized in Table 19. 

Table 19. Costs and installation issues related to implementation of DPF systems 

Vehicle Equip. 

Type Engine Type DPF System DPF cost Mounting Location Mechanic Hours Hardware 

#92128 MTI 1604 

Haul Truck 

BF6M1013 

ECP 

Engelhard 

DPX 9308 $5,500.00 

Original 

DOC 

Brackets 

12 hours mechanical 

$360.00 (move original 

DOC mounts to get trap 

close to turbo)

Structural 

modifications 

Clamps 

Heat Wrap 

$1,400.00 

#92133 MTI 1604 

Haul Truck BF6M1013C CleanAir 

FPA 158W 

$4,800 

purchase 

$20.00/125 

gal FBC 

Original 

DOC 

Brackets 

7 hours mechanical 

$210.00 (to 

install trap as close to the 

turbo as possible)

Clamps 

Heat wrap 

$1000.00 

#92506 MTI 350 

LHD BF4M1013 

DCL 

BlueSky 

3211-SA6CG1-21 

$8,300.00 

filter 

$5,400 regen 

station 

Engine 

hood 

(not 

suitable 

location 

for field 

use)

2 hours electrical, 4 hours 

mechanical $180.00 

Flex Pipe 

Clamps 

$200.00 
83

Vehicle Equip. 

Type Engine Type DPF System DPF cost Mounting Location Mechanic Hours Hardware 

#92506 MTI 350 

LHD BF4M1013 

Donaldson 

P604516 

(Twin side 

by side 

filters) 

$1,500 

housing 

($165.00x2) 

disposable 

filters 

Engine 

hood 

(not 

suitable 

location 

for field 

use)

3 hours mechanical 

$90.00 

Flex Pipe 

Clamps 

$200.00 

#92526 

Elphinstone 

R 1300 

LHD 

CAT 3306 

DITA 

ECS CT 28 

Cattrap 

$8,300 + 

$6,000 for 

spare filter 

(2 filter 

elements are 

required to 

limit 

equipment 

downtime) 

Alongside 

engine on 

side well 

(not 

suitable 

location 

for field 

use)

5 hours mechanical 

$250.00 Would 

require chassis 

modifications for 

permanent 

installation/maintenance

Flex Pipe 

Clamps 

Heat wrap 

$1100.00 

#99942 

Elphinstone 

R 1500 

LHD 

CAT 3306 

DITA 

DCL 

MineX 

5C57 11 

$6,000.00 

Original 

DOC 

Brackets 

2 hours Mechanical 

$60.00 (installed 

in original position)

Heat Wrap 

Clamps 

$1,000.00 

The experiences the mine operators gained with the tested DPF systems during these 

short-term trials are summarized below. 

Engelhard DPX 9308 

The tested Engelhard DPX system was in use at the Stillwater mine for more that 4600 

hours prior to the study. The trap was rotated (end-to-end) twice and baked once since its 

installation. This system worked according to expectations. In cases when it was 

retrofitted to vehicles that were operated over favorable duty cycles, the system was 

found to be a truly passive system. According to the Stillwater mine operators this is 

probably the best choice for their hard working (high exhaust temperature) heavy-duty 

equipment. 

CleanAir Systems FPA 158W 

This system worked as designed and advertised. The system required the use of a fuel 

borne catalyst. The feasibility of blending the fuel borne catalyst with fuel supplies for an 

entire fleet still needs to be investigated. As a general statement, it would require approx. 

$15,000/month to provide the FBC to the whole Stillwater diesel fleet. The effects of the 

FBC on the performance of the diesel oxidation catalytic converters (DOC's) and the 

other exhaust aftertreatment systems is not known at this time. The Stillwater mine 

operators are of the opinion that the cost of the FBC will probably preclude the use of 

CleanAir Systems DPF system. 
84

DCL Blue Sky 3211-SA-6CG1-21 

This active system was originally tested at the Stillwater East Boulder mine but was 

removed due to the failure of the on-board heating element. During the short trial at the 

Stillwater Nye mine this system worked as designed. Some issues that mine operators 

must consider prior to using this system are that it requires downtime for regeneration 

and requires a regeneration station with electric power and a compressed air supply. 

Because electric power is not available in the majority of the production zones in the 

Stillwater mine and historically their equipment does not return to a central station after 

the work shift, the mine operators deemed it as unpractical. 

Mac’s Mining Repair/Donaldson P604516 

This system worked as designed during the short trial at the Stillwater Nye mine. The 

filter elements did not sustain any physical damage during the tests. However, the size of 

the unit and the reputed 100-hr short life span of the filter elements were found to be the 

major obstacles in implementation of this system. The filter life and operational cost 

could not be determined, during this study, due to the limited trial period. The Stillwater 

mine operators do not consider this system to be practical for Stillwater's applications. 

ECS CT 28 Cattrap 

This DPF system uses a cordierite element that was wash coated with a base metal 

catalyst. During these short trials the system was found to work as designed. However, 

because of the short nature of these trials, there was no need to regenerate the filter using 

the CombiClean regeneration station, thus the regeneration system was not evaluated. 

Due to the size of the Cattrap system (14"X36"), major equipment modifications were 

required to install the unit. From the perspective of the Stillwater mine operators the size 

of the unit, its cost ($8,300 initial plus $6.000 for replacement section) and the cost of the 

installation make this system an unlikely candidate. 

DCL MineX 5C57 11 

This passive system was in operation at the Stillwater mine for more than 800 hours prior 

to the study. Originally this system was installed on an LHD #92535 (R-1300) but was 

removed due to high back pressures. The exhaust temperatures generated over the duty 

cycle of this particular machine were not sufficient to secure regeneration of the system. 

Since installed on #99942, the system has worked as designed and did not require any 

maintenance during this period. According to the Stillwater mine operators this system is 

a good choice for high duty cycle machines. 

DPF systems at Stillwater 

Over a dozen filters have been on trial at the Stillwater mine, for a combined total of over 

22,000 hours prior to this study. The majority of the DPF systems are the Engelhard DPX 

9308. Only one of these systems installed on a locomotive was replaced due to a failure 
85

caused by runaway regeneration. The other installed systems have been virtually 

maintenance free. The mine also has had positive experience with the DCL 5C5711 

MineX DPF system. In their opinion this has been a very good system with the only 

problem being the inappropriate selection of an application. The two reasons why DCL 

does not have a larger presence at Stillwater are the company’s desire to standardize their 

equipment and the fact that the Deutz service group, the major supplier of engines to the 

mine, supports the Engelhard DPF systems. 
86

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