Examination of Diesel Aftertreatment Systems at NIOSH Lake 

Lynn Laboratory 

Aleksandar D. Bugarski, George H. Schnakenberg, Jr., Jon A. Hummer, 

Emanuele Cauda, Samuel J. Janisko, and Larry D. Patts 

US Department of Health and Human Services, Public Health Service, Center for Disease Control and Prevention, 

National Institute for Occupational Safety and Health, Pittsburgh Research Laboratory, 626 Cochrans Mill 

Road, Pittsburgh, PA 15236, USA 

Abstract 

A series of engine/dynamometer tests was conducted to assess the effects of three types of 

uncatalyzed diesel particulate filters (DPFs), a diesel oxidation catalytic converter (DOC) and 

three types of high temperature disposable filter elements (HT DFEs) on the concentrations and 

size distribution of diesel aerosols and concentration of nitric oxides in underground mine air. 

Tests were conducted in the NIOSH Diesel Laboratory at the Lake Lynn Laboratory 

experimental mine, a facility developed to allow evaluation of these and other control 

technologies directly in an underground environment. The aforementioned technologies are 

evaluated by comparing the aerosol and gas measurements in the mine air 60 m downstream of 

the exhaust from a naturally aspirated, mechanically controlled engine fitted with the tested 

systems or muffler and operated at four steady-state engine speed and power modes. 

The tested DPF and HT DFE systems caused a 10-fold reduction in total mass concentrations of 

aerosols. The size distribution and number concentration measurements showed that all tested 

DPF systems and HT DFE elements effectively removed accumulation mode aerosols (D50>30 

nm) for all test modes. An increase in peak number concentrations of nucleation mode (D50>30 

nm) diesel aerosols is evident for some of tested DPF systems when engine was operated at highload modes. The effects of uncatalyzed DPFs on nitric oxide (NO) and nitrogen dioxide (NO2) 

concentrations are found to be minor. A four-fold increase in percentages of NO2 in total 

nitrogen oxides (NOx) over baseline case was observed for the DOC when the engine was 

operated at high-load modes. 

The findings from this study should contribute to better understanding the potential for various 

control technologies to reduce exposure of underground miners to nano and ultrafine aerosols. In 

addition, detailed physical characterization of diesel aerosols made directly in occupational 

setting should foster a better understanding of the health risks associated with exposure to nano 

and ultrafine diesel aerosols. 
Introduction 

In recent years, health effects associated with exposure to diesel particulate matter and other 

primarily combustion-generated, nano and ultrafine aerosols have received substantial attention 

from public, government and academia. Pope and coauthors (2002) established that long-term 

exposure to combustion-related fine particulate pollution is an important risk factor for 

cardiopulmonary and lung cancer mortality. There is growing evidence suggesting that particle 

number, surface area, size, or perhaps some associated structural properties may affect 

nanoparticle toxicity, in comparison with larger respirable particles of the same composition 

(Donaldson and Stone, 2003), but in general, occupational health risks associated with exposure 

to nano and ultrafine aerosols are not yet clearly understood. 

In January 2001 the U.S. Mine Safety and Health Administration (MSHA) promulgated 

regulations, 30 CFR 57.5060, limiting exposures of underground metal and nonmetal miners to 

diesel particulate matter (DPM). DPM exposures are currently being regulated solely on the 

basis of the total and elemental carbon mass per unit volume of air. No reference is made to 

either size or the number concentration of emitted particles. Mass-based exposure assessments 

are not always fully predictive of disease risk; in some cases respirable particle surface area and 

detailed surface compositional or morphological properties better correlate with toxicity or offer 

an explanation of seeming anomalies in epidemiological findings of disease risk (Wallace et al., 

1990). Other studies have indicated the importance of complementing mass based exposure 

monitoring with measurements of size, number, and surface area of aerosols in attempt to assess 

adverse health impact of nano and ultrafine aerosols (Donaldson et al. 2000, 2002; Tran et al., 

2000; Englert 2004, Oberdörster et al. 2000, 2004). 

As a result of the new technology-forcing MSHA regulation, the U.S. underground mining 

community is currently working on identifying technically and economically feasible controls 

for the curtailment of DPM and toxic gaseous emissions from existing and new diesel powered 

equipment in underground mines. Various diesel emission control technologies, including diesel 

oxidation catalytic converters (DOCs), diesel particulate filters (DPFs) systems and hightemperature disposable filter elements (HT DFEs) are some of the tools available to the industry 

to control DPM emissions. 

The majority of the work on size resolved characterization of diesel aerosols was done in 

laboratory environments (Bugarski 1999, Maricq et al. 1999, 2004, Vaaraslahti et al. 2004, 

Ntziachristos and Samas, 2006), on the road (Kittelson et al. 2005) and tunnels (Gautam et al. 

2003, Jamriska et al 2004). Several researchers (McGinn et al. 2004, Bugarski et al. 2006a and 

2006b) studied to a limited extent the effects of selected control technologies on concentrations 

of aerosols in underground mines. 

Since the aerosol size and concentrations of semivolatile materials emitted by diesel engines in 

the work place are strongly influenced by a number of processes and ambient conditions, the best 

way to characterize them is to sample directly in an occupational setting. The facility developed 

at the NIOSH Lake Lynn Laboratory (LLL) enables the investigation of diesel emissions control 

technologies in underground environment with laboratory precision and accuracy. 
Methodology 

Three types of non-catalyzed DPF systems using Cordierite, silicon carbide (SiC), and sintered 

metal filter elements, two types of HT DFEs, and a DOC are examined in this study. The sintered 

metal system was used with a fuel-born catalyst. The objective was to study the effects of these 

exhaust aftertreatment technologies on the physical properties of diesel aerosols and gases and 

compare those with the effects observed for a standard muffler. The testing was conducted using 

the NIOSH Diesel Laboratory at the NIOSH Lake Lynn Laboratory (LLL). 

NIOSH Diesel Laboratory 

The NIOSH Diesel Laboratory is situated in the D–drift of the LLL experimental mine (Figure 

1). The LLL was developed from an underground limestone mine situated near Fairchance, 

Pennsylvania, about 97 km (60 miles) southeast of Pittsburgh, PA, and 16 km (10 miles) 

northeast of Morgantown, WV (Tribsch and Sapko 1990). 

Figure 1. NIOSH Lake Lynn Laboratory Experimental Mine 

The D-drift is approximately 530 m (1750 ft) long, 6 m (20 ft) wide, and 2 m (7 ft) high. A 

schematic of the laboratory layout is shown in Figure 2. The major components of the laboratory 

are an engine/dynamometer system, three sampling and measurement stations, and a ventilation 

measurement and control system. 
Figure 2. NIOSH Diesel Laboratory in D-drift of LLL 

Dynamometer/Engine System 

A water-cooled eddy-current dynamometer from SAJ (Pune, India, Model SE150) rated at 150 

kW (201 bhp) is used to load and control a naturally aspirated, mechanically controlled Isuzu 

C240 diesel engine (Isuzu Motors Limited) (Figure 3). The Isuzu C240 is one of the most 

popular engines in U.S. underground coal mines and is primarily used to power light-duty 

vehicles. 

Figure 3. Dynamometer/Isuzu C240 system 

A Model Dyn-Loc IV dynamometer controller and a Model DTC-1 engine throttle controller 

(DyneSystems Co. Germantown, WI ) provide control for the dynamometer and the engine, 

respectively. A DyneSystems “Companion” data acquisition system is used to acquire relevant 

dynamometer and engine operating parameters. Both controllers and data acquisition system are 

operated using CellAssistant for Windows software from DyneSystems. 

The potential effects of the dynamometer cooling process on the test results are eliminated by 

placing the cooling system approximately 30 m downwind of the downstream sampling station. 
 

Monitoring Stations 

Ambient Stations 

Ambient concentrations of aerosols and gases are measured in the mine air upstream and 

downstream of the dynamometer/engine system (Figure 2). The upstream ambient monitoring 

station is located approximately 60 m (197 ft) up wind of the dynamometer. This station is 

designed to measure background aerosol concentrations using following methods: 

1.	 The Tapered Element Oscillating Microbalance (TEOM) Series 1400a (Thermo Electron 

Corp., East Greenbush, NY) ambient particulate monitor is used for real time 

measurements of total particulate matter under 0.8 μm; 

2.	 The Scanning Mobility Particle Sizer (SMPS) (TSI, St. Paul MN) is used to measure size 

distribution and count concentrations of aerosols between 10 and 408 nm. 

The downstream ambient monitoring station is located about 60 m (197 ft) downwind of the 

dynamometer. This station is designed to measure concentrations of aerosols and gases using the 

following instrumentation: 

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

measurements of total particulate matter under 0.8 μm;
 

2.	 The SMPS was used to measure size distribution and number concentrations of aerosols; 

3.	 The Fast Mobility Particle Sizer (FMPS) (Model 3091, TSI) was used to measure size 

distribution and number concentrations of aerosols; 

4.	 Electrical Low Pressure Impactor (ELPI), (Model DAS 3100, Dekati, Finland) was used 

to measure size distribution and number concentrations of aerosols. 

5.	 Chemiluminescence NO/NO2 analyzer Model CLD 700 AL, Eco Physics, Duernten, 

Switzerland; 

6.	 CarbonCap hand-held recording CO2 meter (Model GM70, Vaisala Oyj, Helsinki, 

Finland) to which a HM-70 probe is added to measure relative humidity and temperature. 

Engine/Dynamometer and Tailpipe Station 

Concentrations of CO and CO2 in the raw exhaust of the test engine are measured upstream of 

emissions control system using a Model 602 Series non-dispersive infrared (NDIR) analyzer 

(California Analytical Instruments, Incorporated, Orange, CA). 

Pertinent engine and ambient parameters are measured and recorded at this location as well. The 

details are given below. 

Instrumentation 

Total Aerosol Mass Concentration Measurements 

At the upwind and downwind locations, ambient concentrations of total particulate matter are 

measured with the TEOM ambient monitor. The TEOM flow rate is set at 2.0 lpm. A 10-mm 

Dorr-Oliver cyclone followed by a diesel particulate matter cassette (SKC) with its filter element 

removed are used to pre-classify aerosols entering the TEOM, allowing only particles with an 

average aerodynamic diameter (50dae) smaller than 0.82 μm to reach the collection filter. The 
average concentrations for a test are obtained from the difference in filter masses recorded at the 

start and stop times. 

Aerosol size Distribution and Total Number Concentration Measurements 

Aerosol size distributions and concentrations at downstream station are measured using an 

SMPS. The second SMPS is used to measure size distributions and concentrations at the 

upstream station. 

The SMPS at the downstream station is configured with an electrostatic classifier (EC) Model 

3080L and a condensation particle counter (CPC) Model 3025A. The SMPS at the upstream 

sampling station consists of an EC Model 3080L and a CPC Model 3776. Both SMPSs are used 

to measure size distribution and number concentrations of particles in the range between 10 and 

408 nm. The sample and sheath air flows in both ECs are maintained at 0.6 l/min and 6 l/min, 

respectively. The inlet impactor 50dae for these conditions is 480 nm. The CPC is operated in 

high-flow mode to minimize diffusion losses. The instruments are operated using a dedicated 

laptop computer and Aerosol Instrument Manager Software Version 8.0.0.0 from TSI. Multiple 

charge and diffusion correction are applied on all data. 

Concentrations of Nitric Oxide, Nitrogen Dioxide, Carbon Monoxide, 

Carbon Dioxide and Hydrocarbons 

Concentrations of nitric oxide (NO) and nitrogen dioxide (NO2) at the downstream station are 

measured with a Model CLD 700 AL chemiluminescence (CLD). The CarbonCap hand-held 

meter Model GM70 is used to measure carbon dioxide (CO2) concentrations at the downstream 

station. 

A Model 602 Series non-dispersive infrared (NDIR) analyzer is used to measure CO and CO2 

concentrations in the tailpipe. A portable gas conditioning system Model PSS-10 (M&C 

Products Analysentechnik GmbH, Ratingen, Germany) is used for conditioning samples prior to 

measurement. 

Engine and Dynamometer Parameters 

The exhaust mass flow rate (Mex) was calculated from results of air intake and fuel flow rate 

measurements. The engine air intake volumetric flow rate is measured using laminar flow 

element (LFE) Model 50MC2-4 (Meriam Instruments, Cleveland, OH). The fuel mass flow rate 

is measures using Max 710 Fuel Measurement System with flow meter Model 213-310 (Max 

Machinery Inc., Healdsburg, CA). The system can measure diesel fuel flow rates between 0.12 

and 175 lbs/hr with 0.5% accuracy. The density of the fuel obtained from the fuel analysis is 

used as input to the instrument. The flow rates are corrected for variations in temperature, 

pressure, and relative humidity. 

The exhaust temperature was measured using a Model KMQSS-125G-6, K-type thermocouple 

(Omega, Inc). The engine backpressure was measured using a Model P356 differential pressure 

sensor (Kavlico Corp., Moorpark, CA). The output from the thermocouples and pressure sensors 

are collected using the “Companion” data acquisition system mentioned earlier. 
 

 

 

 

Ventilation 

Fresh air is supplied to the LLL underground facility via a ventilation shaft located in E-drift 

(Figure 1 and Figure 2). A Series 2000 Model 48-26-1770 XP Axivane fan (Joy Technologies 

Inc., New Philadelphia, OH) is used to push air into the mine. A portion of available air is 

diverted to the test zone via the E-drift that is situated immediately upwind and normal to the Ddrift. A plywood wall near the downwind exit of D-drift completely blocks the drift except for 

sealed double doors (kept closed during testing) and a circular opening through which all of the 

D-drift air flows. A subsonic venturi meter (Primary Flow Signal, Inc., Tulsa OK) is sealed into 

the circular opening and measures total flow through the D-drift. The meter is connected to a 3­

m section of duct followed by a Series 1000 Model 23-17-3450 Axivane fan (Joy Technologies) 

which maintains the ventilation flow rate through the D-drift. The flow rate measurements are 

compensated for variations in temperature, pressure, and humidity. Air quantities supplied to Ddrift can be regulated by adjusting a bypass vent on the Venturi/auxiliary fan system. 

The average ventilation flow rate in the D-drift throughout all tests was 5.69 ± 0.06 m3

/s 

(12056.4 ± 118.7 ft3

/min). The resulting exhaust dilution ratios at the downstream sampling 

station, calculated using results of exhaust gas and ventilation mass flow rate measurements, for 

R50, R100, I50, and I100 engine operating modes were 148, 149, 186, and 188, respectively. 

Fuel 

The engine was fueled with ultra-low sulfur diesel fuel procured from Guttman Oil (Belle 

Vernon, PA). The fuel was supplied to the engine from the 200-liter main fuel tank (Rohmac 

Inc., Mt. Storm, WV). The results of the analysis performed on that fuel by Core Laboratories, 

Houston, TX are given in Table 1. 

Table 1. Fuel properties 

Test Method Result Units 

BTU, Net ASTM D-240 43468 kJ/kg 

Cetane Number ASTM D-613 61.8 -

Density ASTM D-4052 0.8038 gm/ml 

Flash Point, PMCC ASTM D-93A 62.2 °C 

Hydrocarbon Type 

Aromatics ASTM D-1319 7.2 LV% 

Olefins ASTM D-1319 1.1 LV% 

Saturates ASTM D-1319 91.7 LV% 

Oxygen Content 3.45 Wt. % 

Sulfur Content ASTM D-5453 11 mg/kg 

The sintered metal DPF system was tested using the same fuel to which was added the fuel-borne 

catalyst from Innospec Limited, Cheshire, United Kingdom. The additive was premixed with 

diesel fuel at approximately 0.677 ml of additive per liter of fuel before it was added to auxiliary 

fuel tank on-board the dynamometer/engine system. 
 

Test Protocol 

The effects of aftertreatment devices were established by comparing results from a series of 

steady-state tests conducted both with the aftertreatment systems and with the muffler. The Isuzu 

C240 engine was operated at four steady-state engine operating modes. The description of the 

test modes is given in Table 2. 

Table 2. Engine operating modes 

Mode Description Engine Speed Torque Power 

Rpm Nm kW 

R50 Rated speed 50% load 2950 55.6 17.2 

R100 Rated speed 100% load 2950 111.2 34.3 

I50 Intermediate speed 50% load 2100 69.1 14.9 

I100 Intermediate speed 100% load 2100 136.9 30.6 

In a typical test run, the engine was operated for approximately three hours at the selected engine 

mode. The initial hour of each test was dedicated to achieving system equilibrium. The 

measurements were initiated at the beginning of the second hour. The data shown in this report 

are results of averaging data obtained over the last hour of the test. 

Aftertreatment Technologies 

The aftertreatment devices tested in this study are listed in Table 3. 

Table 3. Aftertreatment technologies 

Technology Supplier 

Cordierite 

DOC Engine Control Systems Ltd., Newmarket, Ontario, Canada, Purifier, PN#A16-0130 

Cordierite DPF Catalytic Exhaust Products, Toronto, Ontario, Canada, Model 912-SXT 

SiC DPF DCL International Inc., Concord, Ontario Canada, Model Minex Sootfilter, Model 

5.66×10 

Sintered Metal 

DPF Mann+Hummel GMBH, Speyer, Germany, Model SMF-AR 

DFE #1 Donaldson, Minneapolis, MN PN#604516 

LDFE Laundered Donaldson , Minneapolis, MN PN#604516 

DFE #2 Filter Service & Testing, Huntington, UT, PN#11526 

The Cordierite diesel particulate filter (DPF) system consisted of one 254×305 mm (10×12 in) 

filter element. The silicon carbide (SiC) DPF system was designed with two 144×254 mm 

(5.7×10 in) filter elements installed in parallel. The sintered metal (SM) DPF had a single filter 

unit with total surface area of 2.75 m2. All DPF systems were designed to maintain engine 

backpressure below 10.21 kPa (41 in H2O), the engine manufacturer-specified maximum 

allowable value. 

Cordierite and SiC systems used uncatalyzed elements. The SM DPF system was tested in 

conjunction with the iron-based fuel borne catalyst. The testing of Cordierite and SiC elements 

was initiated after the systems were operated for more then 20 hours and subsequently 
regenerated using a CombiClean regeneration station (Engine Control Systems Ltd.). The SM 

DPF system testing was started after the system accumulated approximately 4 hours of operation. 

The HT DFEs were tested using a custom housing designed and built by Mac’s Mining Repair 

Service (Huntington, UT). Since the HT DFEs we tested are approved for use in applications 

where exhaust temperatures do not exceed 343 oC (650 oF), it was necessary to integrate an airto-air heat exchanger (supplied by Mac’s Mining Repair) into the exhaust system between the 

engine and the HT DFE housing. Two DFE #1 were tested: one as new and a different one after 

laundering (LDFE) by Mac’s Mining Repair Service. The DFE #2 was tested only as new. 

The average exhaust temperatures observed for four test modes are summarized in Table 4. It is 

important to note that exhaust temperatures were significantly lower for the HT DFE systems. 

Table 4. Average exhaust gas temperatures 

Mode 

DPF,DOC, Muffler HT DFE 

Exhaust 

Temperature at 

Inlet of Device 

Exhaust 

Temperature at 

Outlet from 

Device 

Exhaust 

Temperature at 

Inlet of Device 

Exhaust 

Temperature at 

Outlet from 

Device 

oC oC oC oC 

R50 306 258 200 154 

R100 529 436 329 242 

I50 254 216 160 125 

I100 485 402 313 234 
 

Results 

Effects on Aerosol Size Distributions and Number Concentrations 

The results of size distribution measurements at the downstream sampling station measured with 

the SMPSs are summarized in Figure 4, Figure 5, Figure 6, and Figure 7. dN/dlog(D_p) [#/cm^3]

1.00E+07 

R50 

1.00E+06 

1.00E+05 

Muffler
 

DOC 1.00E+04 

Cordierite DPF
 

SiC DPF
 

Sintered Metal DPF
 1.00E+03 DFE #1
 

LDFE #1
 

DFE #2
 

1.00E+02 

1 10 100 1000 

D_p [nm] 

Figure 4. Aerosol size distribution measured during R50 tests 
dN/dlog(D_p) [#/cm^3] dN/dlog(D_p) [#/cm^3]

1.00E+07 

R100 

1.00E+06 

1.00E+05 

Muffler
 

DOC 1.00E+04 

Cordierite DPF
 

SiC DPF
 

Sintered Metal DPF
 1.00E+03 DFE #1
 

LDFE #1
 

DFE #2
 

1.00E+02 

1 10 100 1000 

D_p [nm] 

Figure 5. Aerosol size distribution measured during R100 tests 

1.00E+07 

I50 

1.00E+06 

1.00E+05 

Muffler
 

DOC 1.00E+04 

Cordierite DPF
 

SiC DPF
 

Sintered Metal DPF
 1.00E+03 DFE #1
 

LDFE #1
 

DFE #2
 

1.00E+02 

1 10 100 1000 

D_p [nm] 

Figure 6. Aerosol size distribution measured during I50 tests 
dN/dlog(D_p) [#/cm^3]

1.00E+07 

I100 

1.00E+06 

1.00E+05 

Muffler 

DOC 1.00E+04
 

Cordierite DPF
 

SiC DPF 

Sintered Metal DPF
 1.00E+03
 DFE #1 

LDFE #1 

DFE #2 

1.00E+02 

1 10 100 1000 

D_p [nm] 

Figure 7. Aerosol size distribution measured during I100 tests 

From the presented distributions one can conclude the following: 

1.	 The DOC had relatively moderate effect on the size distribution of diesel aerosols in mine 

air. 

2.	 All tested DPF systems and DFE elements effectively removed accumulation mode 

aerosols (50dae >30 nm) from mine air for all test modes. 

3.	 Concentrations of nucleation mode aerosols (50dae <30 nm) were found to be substantially 

higher when the engine was operated at the higher load and higher exhaust temperature 

modes, R100 and I100, than at the lower load and lower temperature modes, R50 and I50 

indicating positive correlation between concentrations of nucleation mode aerosols and 

exhaust temperatures (see Table 2). 

Effects on Total Number and Mass Concentrations of Aerosols 

The results of SMPS (downstream and upstream) and ELPI (downstream) measurements are 

used to calculate the effects of tested control technologies on changes in aerosol number 

concentration in mine air. The effects of the technologies on mass concentrations are calculated 

using TEOM data. The changes are summarized in Figure 8. 
 

 

100 

Total Concentration Change [%] 

80 

R50 

60 

40 

20 

0 

-20 

Cordierite 

DOC 

Cordierite 

DPF SiC DPF Sintered Metal DPF DFE #1 LDFE DFE #2 

SMPS 8.6 81.3 20.6 95.4 99.6 97.8 96.3 

ELPI -19.9 74.1 12.9 90.0 96.6 94.2 91.7 

TEOM 34.9 97.3 90.2 91.5 88.4 99.4 74.6 

Engine Operating Mode 

Figure 8. Percentage of total number and mass concentrations change for R50 test modes 

100 

Total Concentration Change [%] 

80 

R100 

60 

40 

20 

0 

-20 

Cordierite 

DOC 

Cordierite 

DPF SiC DPF Sintered 

Metal DPF DFE #1 LDFE DFE #2 

SMPS 9.3 95.3 62.2 -16.7 75.0 65.6 68.8 

ELPI 33.4 95.2 77.1 19.5 69.8 56.3 61.9 

TEOM 11.7 97.4 97.8 96.6 98.4 95.1 95.2 

Engine Operating Mode 

Figure 9. Percentage of total number and mass concentrations change for R100 test modes 
 

 

100 

Total Concentration Change [%] 

80 

I50 

60 

40 

20 

0 

-20 

-40 

Cordierite 

DOC 

Cordierite 

DPF SiC DPF Sintered 

Metal DPF DFE #1 LDFE DFE #2 

SMPS 8.2 88.5 94.6 94.5 93.3 98.3 99.2 

ELPI -13.3 86.1 93.8 90.8 84.0 95.6 98.5 

TEOM -31.1 87.2 91.7 97.1 97.7 89.9 

Engine Operating Mode 

Figure 10. Percentage of total number and mass concentrations change for I50 test modes 

0 

10 

20 

30 

40 

50 

60 

70 

80 

90 

100 

Total Concentration Change [%] 

SMPS 21.6 94.0 83.3 58.6 76.6 96.1 94.0 

ELPI 43.2 96.3 92.3 86.0 81.4 95.8 94.8 

TEOM 41.7 99.5 99.0 99.7 99.2 98.9 99.4 

Cordierite 

DOC 

Cordierite 

DPF SiC DPF Sintered Metal DPF DFE #1 LDFE DFE #2 

I100 

Engine Operating Mode 

Figure 11. Percentage of total number and mass concentrations change for I100 test modes 

The results indicate the following: 
 

1.	 The effects of the DOC on number and mass concentrations were found to be engine 

operating mode dependent. The results indicate that the effects of DOC on number and 

mass concentrations were the most pronounced for high-load and high-temperature I100 

engine operating modes. 

2.	 The tested DPF and DFE systems in the majority of test cases caused a 10-fold reduction 

of the total mass concentrations measured by TEOM. 

3.	 In the majority of the cases total mass reductions were accompanied with comparable 

reductions in total number concentrations. The exceptions were the cases (e.g. SiC DPF 

@ R50, SM DPF @ R100) when high concentrations of nucleation particles resulted in 

significantly lower reductions or even an increase in total particle number. 

Effects on NO and NO2 concentrations 

The results of measurements of nitric oxide (NO) and nitrogen dioxide (NO2) concentrations at 

the downstream station are used to calculate concentrations of total nitric oxides (NOx = NO+ 

NO2) and percentages of NO2 in total NOx. The NOx concentrations are summarized in Figure 

12, while the percentages of NO2 in total NOx are shown in Figure 13. NOx Concentrations [ppm] 

4 

3 

2 

1 

0 

Muffler 

Cordierite DOC 

Cordierite DPF 

SiC DPF 

Sintered Metal DPF 

DFE #1 

LDFE 

DFE #2 

1 2 3 4 

1.88 2.65 1.79 1.74 

2.05 3.32 2.28 2.51 

1.76 2.65 1.84 1.92 

1.89 3.00 1.85 1.96 

1.74 2.98 1.69 1.90 

2.27 2.22 1.99 1.76 

1.58 2.47 1.64 1.73 

1.80 2.29 1.44 1.59 

Technology

Figure 12. NOx Concentrations [ppm] 
0 

5 

10 

15 

20 

25

NO2 / NOx Concentrations [%] 

Muffler 19.5 3.6 15.2 3.5 

Cordierite DOC 13.9 13.4 4.6 13.2 

Cordierite DPF 6.6 1.6 8.4 1.5 

SiC DPF 6.7 2.6 8.1 2.9 

Sintered Metal DPF 7.7 1.7 9.4 3.0 

DFE #1 15.9 3.4 23.6 2.6 

LDFE 10.8 1.2 15.1 1.0 

DFE #2 2.9 3.2 21.0 3.0 

R50 R100 I50 I100 

Technology 

Figure 13. NO2 percentages in total NOx concentrations 

The results showed the following: 

1.	 The effects of the control technologies on NOx concentrations are found to be minor. The 

average values and standard deviations for R50, R100, I50, and I100 modes are 

1.87±0.20, 2.70±0.36, 1.81±0.23, and 1.89±0.26, respectively. 

2.	 The percentages of NO2 in total NOx are found to be strongly dependent on engine 

operation mode / exhaust temperature. 

3.	 The four fold increase in percentages of NO2 in total NOx over baseline case was 

observed for the DOC when the engine was operated at R100 and I100 (high exhaust 

temperature) modes. The same DOC did not promote oxidation of NO to NO2 in the 

cases when engine was operated at the lower temperature R50 and I50 modes. 

4.	 The substantial increase in NO2 fraction in total NOx was observed for DFE#1 and 

DFE#2 when the engine was operated at the I50 mode. 
Conclusion 

The series of the tests was conducted in the ventilated drift in the NIOSH Diesel Laboratory at 

the Lake Lynn Laboratory experimental mine with objective of studying the effects of selected 

aftertreatment technologies on the concentrations and size distribution of diesel aerosols and 

concentration of nitric oxides in underground mine air. The facility was developed to allow 

direct measurements in an underground mine occupational setting. The analysis was performed 

on the results of tests conducted at four steady state modes for the engine equipped with three 

different types of uncatalyzed DPFs, three different types of HT DFEs, a DOC, and a muffler. 

The results obtained with muffler were used to establish baseline case. 

According to TEOM results, the tested DPF and DFE systems reduced the total aerosol mass 

concentrations by approximately 10 fold for majority of the test modes. That finding 

corroborated with findings from size distribution and number concentration measurements that 

showed that all tested DPF systems and DFE elements effectively removed accumulation mode 

aerosols (50dae >30 nm) from mine air. Substantial increase in peak number concentrations of 

nucleation mode (50dae >30 nm) aerosols was evident for SiC and SM DPF systems when engine 

was operated at R100 and I100 engine operating modes. The effects of DOC on number and 

mass concentrations were found to be engine operating mode i.e. exhaust temperature dependent. 

The 31 percent increase in aerosol mass was observed when DOC was tested at I50 mode. The 

effects of uncatalyzed DPFs on NO and NO2 concentrations are found to be minor. The four fold 

increase in the NO2 to NOx fraction over the baseline case was observed for the DOC when the 

engine was operated at high-load engine operating modes. 

The findings from this study should contribute to better understanding the potential for tested 

control technologies to reduce exposure of underground miners to nano and ultrafine aerosols 

without potential increase in exposures to nitrogen dioxide. In addition, better understanding of 

physical characteristics of diesel aerosols present in occupational setting should help better 

assessment of the health risks associated with exposure to nano and ultrafine diesel aerosols. 

Disclaimer 

The findings and conclusion of this publication have not been formally disseminated by the 

National Institute for Occupational Safety and Health and should not be constituted to represent 

any agency determination or policy. Mention of any company or product does not constitute 

endorsement by NIOSH. 
References 

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