Field Evaluation of Diesel Particulate Matter Using Portable 

Elemental Carbon Monitors 

S. Janisko & J.D. Noll 

National Institute for Occupational Safety and Health (NIOSH), Pittsburgh, Pennsylvania, USA 

ABSTRACT: Regulations on worker exposure to diesel particulate matter (DPM) are becoming increasingly 

stringent in the mining industry. Due to the complexity and unpredictability of this aerosol, there is a need for new 

tools to help mines develop an effective strategy to reduce DPM concentrations. To address these needs, NIOSH 

has developed a portable elemental carbon monitoring device for use in underground mines. This instrument is 

compact and capable of monitoring EC concentrations in real time. The information that it provides is useful 

when planning new DPM curtailment strategies or when measuring the effectiveness of existing DPM controls. 

The following paper discusses a variety of ways that this instrument has been used to help lower DPM 

concentrations and exposure to DPM in active mines. 

1 Introduction 

In May, 2008, the Mine Safety and Health Administration 

significantly lowered the permissible exposure limit of 

underground mine workers in the U.S. to diesel particulate 

matter (DPM). The new regulation states that “a miner’s 

personal exposure to diesel particulate matter in an 

underground mine must not exceed an average eight-hour 

equivalent full shift airborne concentration of 

160 micrograms of total carbon per cubic meter of air 

(160 TC μg/m3

)”, where TC is the sum of elemental 

carbon (EC) and organic carbon (OC) (MSHA, 2005). This 

adjustment is a substantial reduction from the 2007 interim 

limit of 350 TC μg/m3

. 

In order to comply with this regulation, most mines 

must employ one, or a number of combined control 

strategies to lower DPM concentrations. Some options 

available to mines include: improved vehicle maintenance 

programs, increased or re-routed ventilation, upgrading 

fleet to newer engines, use of alternative fuels such as 

biodiesel, the addition of diesel particulate filters (DPFs) to 

key vehicles, changes to truck traffic and other 

administrative controls. Because these strategies vary 

greatly in the amount of reductions attainable and the costs 

of implementation, it is important to have a thorough 

understanding of the DPM emissions within the mine so 

that the most effective control strategy can be utilized. 

Obtaining a clear understanding how individual DPM 

sources impact the transient concentrations of DPM within 

a mine is a difficult task, but recent advancements in 

measurement techniques have made this goal more 

feasible. 

1.1 Real-time Monitoring 

Currently, there are no instruments available to the mining 

industry for measuring DPM concentrations that are 

portable and field-worthy. The traditional method for 

measuring DPM in underground mines is based on the 

NIOSH 5040 method (Birch and Cary, 1996; Birch, 2002). 

Although this procedure may be the most accurate method 

for collecting and measuring compliance samples of DPM, 

the time and cost involved in the process make it a less 

practical method for mines that are looking to monitor the 

effectiveness of DPM controls. In addition, the NIOSH 

5040 method is a one-dimensional measurement, meaning 

that it provides an average DPM exposure measurement 

over a given time period without recording critical 

information pertaining to the cause of the overexposure. 

To address these issues, NIOSH has developed a portable 

instrument that is capable of indicating the concentration 

of DPM in near real-time. By tracking the changes in laser 

beam transmittance through a particulate matter collection 

filter over time, the instrument is able to measure the rate 

of EC deposition on the filter based on previous calibration 

against the NIOSH 5040 method. This combined data set 

(time and sensor rate of change) correlates with EC 

concentrations within the tested location (Noll & Janisko. 

2007). If desired, an optional EC to TC ratio can be set 

within the instrument settings to correlate this value to TC, 

however caution is advised when utilizing this method (see 

section 1.2). Using this process, the instrument provides 

charted outputs of recorded EC and calculated TC 

concentration changes over time. Because these 

concentrations are often transient in nature, understanding 

this data will help mine operators obtain a clearer picture 

of how DPM levels are affected by mining activity and 

how well they respond to different control strategies. This 

data can provide valuable information on the effectiveness 

of ventilation, vehicle-specific emissions, DPF failures, 

miner-specific exposures, and the effectiveness of cab 

filtration systems. The following is a discussion on how 

real-time monitoring technology can be used to evaluate 

DPM problem areas and aid in the selection of effective 

DPM control strategies. 

1.2 Capabilities, Limitations and Interferences 

The instruments used for real-time assessment of DPM are 

beta prototypes supplied by ICx technologies (Figure 1). 
Figure 1 A photograph of the ICx DPM Monitor beta 

prototype showing the instrument, sampling line 

and size selector. 

 

These devices rely on a rolling average to evaluate EC 

levels1

. 

1

 A further technical description of the operation of the 

instrument is provided in previous publications: Janisko et 

al., 2008; Noll & Janisko, 2007. 

Therefore, when used as an area sampler or a 

personal sampler, they provide an indication of the average 

concentrations of EC over the previous five, ten and fifteen 

minutes as well as the time-weighted average exposure 

value (TWA) for an eight hour shift. All of these 

calculated values are updated once per minute. The lower 

limits of quantification of the instrument are as follows; 

18 ug/m3

 EC for TWA, 110 ug/m3 EC for five minute 

rolling averages, 62 ug/m3

 EC for ten minute rolling 

averages, and 54 ug/m3

 EC for fifteen minute rolling 

averages. The instruments show an approximate error 

within 10% EC of the NIOSH 5040 method in controlled 

laboratory tests and within 15% EC in field tests (Noll & 

Janisko, 2007; Janisko et al., 2008) 

As with most technologies, the information that the 

DPM monitors provide is subject to certain limitations and 

interferences. First, the monitors use EC as a surrogate to 

estimate DPM and, therefore, do not perform any direct 

measurement of TC. This means that, in countries without 

an EC standard (such as the United States), an EC to TC 

ratio must be set on the instrument in order to convert EC 

measurements to TC. Research on specific conversion 

factors in underground mines has been presented in 

previous investigations (Noll et al., 2007). For compliance 

sampling, MSHA requires that a simultaneous conversion 

factor be obtained from an area sample collected in the 

main exhaust and downstream of the exposed mineworker 

(MSHA, 2008). Although it is encouraged that the 

instruments be utilized primarily for the measurement of 

EC, if TC estimations are desired, it is suggested that 

mines obtain EC/TC ratios in a manner similar to the 

MSHA compliance method. 

When used as directed, mineral dust will not interfere 

with the monitor’s reading in metal/non-metal mines. 

However, when the monitors are exposed to drastic 

changes in temperature from cold to hot, condensation can 

build up on the sampling cassette within the instrument 

and cause false overestimations of EC concentration. This 

interference has been seen primarily in cold climates and 

lasts for only a short duration. Typically, it occurs when 

traveling from a warm section of the mine to the intake. 

After a short time, the system will equilibrate and the 

monitor will begin functioning properly. This interference 

is recognizable in the data as large abnormal spikes that 

correlate with times when the monitor was exposed to 

drastic changes in temperature (07:50-08:15 of Figure 2). 

Another method for detecting this interference is to 

analyze a chart of the sensor output throughout a test. 

Under normal conditions, the sensor voltage will decrease 

or remain constant throughout the testing period. If the 

signal ever rises (as it does around 08:07-08:15 of 

Figure 3), this is a good indicator that a temperature 

interference has occurred. In Figure 2, the data before and 

after the interference would still be accurate. 

2	 Methodology and Results 

2.1	 Sampling Techniques 

The following tests were performed at active mines. 

Depending on the nature of the test, DPM concentrations 

were either read directly from an LCD screen on the 

instrument at the time of testing or downloaded from the 

internal memory of the instrument after the testing period. 

2.2	 Measuring the Effectiveness of Ventilation in an 

Area 

Adjusting the mine’s ventilation system can be one of the 

easier and more cost effective solutions when combating 

DPM emissions. However, it is important to understand 

how successful these ventilation increases will be before 

committing to this control strategy. The DPM monitors 

may be used to measure the adequacy of ventilation in an 

area (in terms of DPM flushing) and to estimate the point 

at which further increases become inefficient when 

weighed against the increased cost and complexity of such 

a solution. 

Figures 4 & 5 show data that was collected in two 

active metal/non-metal mines in 2009. In the first case, 

data was collected at the main exhaust for approximately 

six hours. The monitor was left unattended during the test 

period. As shown, the concentration of EC built slowly, 

but steadily, throughout the test. This is a “fingerprint” 

trend which indicates that a ventilation increase might be 

successful at lowering DPM concentrations. 
Figure 2 A chart of EC concentration vs. time, showing temperature interference at 07:50-08:15. 

Figure 3 A corresponding chart of sensor output showing an increase in signal at 08:07 

. 

Figure 4 A chart showing a steady increase in recorded EC concentration from 200 to 400 ug/m3

 throughout a six hour time 

frame. 
Often times, attaching the DPM monitors to the 

exterior of a vehicle is a superior method of collecting data 

in an area because it can be collected near the center of the 

entry and directly within the working zone. Figure 5 shows 

a case where area measurements were collected on a 

mucker (an LHD, or load haul dump vehicle) during its 

working cycle. Although these types of measurements are 

more prone to fluctuation from localized activity, a similar 

trend can still be found in the data (Figure 5). 

Figure 5 A chart showing a fluctuating, but overall increase in recorded EC concentration from 75 to 200 ug/m 3

 throughout 

a six hour time frame. 

Both of these examples highlight the advantages of 

real-time monitoring as well as full-shift sampling when 

analyzing DPM conditions in an area. Without a longterm, real-time measurement of EC transients, increases in 

DPM concentrations throughout the shift may have gone 

undetected. 

Although not available at the time, a good method for 

assessing the effectiveness of ventilation changes to that 

area would be to increase the air flow to that section of the 

mine without changing any other parameters that would 

influence DPM concentration levels (truck traffic, changes 

in work flow, etc.). From this, some measure of how much 

additional air flow equals a particular reduction in DPM 

concentration could be derived. 

2.3 Monitoring Vehicle-specific Contributions to DPM 

When choosing a DPM reduction solution, it is often 

assumed that diesel particulate filters are the preferred 

method for controlling particulate emissions. Although 

these filters have shown the potential to drastically reduce 

DPM emissions (Bugarski et al., 2007; McGinn et al., 

2002), they can present additional up-front costs and 

maintenance demands (US EPA, 2007) as well as concerns 

over increased NO2 emissions in catalyzed systems 

(Czerwinski et al., 2007; Mogenson et al., 2009). For these 

reasons, it is not uncommon to find cases where it would 

be more efficient to single out the major contributors to 

DPM emissions within a mine’s fleet and outfit those 

vehicles with particulate filters while attacking the rest of 

the fleet with other methods such as enhanced maintenance 

programs, administrative controls or alternative fuel 

blends. In these cases, it would be beneficial to know the 

individual contributions of particular vehicles to total DPM 

emissions throughout the mine (i.e., the vehicle-specific 

emissions) so that the most effective plan could be 

developed. 

2.3.1 Isolated zone testing for vehicle-specific emissions 

A good technique available for measuring vehicle-specific 

DPM contributions is an isolated zone analysis. When 

performing these tests, a vehicle is operated in an inactive 

section of the mine which is as free from DPM 

interference as possible (i.e. the isolated zone) (McGinn et 

al., 2002; Bugarski et al., 2005, 2006). The goal is to 

mimic the typical loading cycle of that engine under 

normal operating conditions. This is accomplished by 

running the machine through a simulation of its working 

cycle within the isolated zone throughout the length of the 

testing period. The benefit of this type of analysis is that it 

more closely replicates engine transients than other forms 

of vehicle-specific testing. The primary limiting factors are 

the ability to maintain prevailing ventilation conditions and 

accurately simulate working cycles. For a detailed 

description of isolated zone methodology, the reader is 

referred to: “Performance Evaluation of Diesel Particulate 

Filter Technology in the Underground Environment”, 

McGinn et al., 2002, and “Evaluation of Diesel Particulate 

Filter Systems and Biodiesel Blends in an Underground 

Mine”, Bugarski et al., 2005. 

Figure 6 shows real-time measurements that were 

taken during an isolated zone test in a metal mine in 2009. 

In this experiment, a mucker was operated within the 

isolated zone, moving ore with the air flow, from the 

upstream end to the downstream end in a continuous cycle. 

Two breaks in testing occurred at 11:32 and 13:47. DPM 

monitors were placed both upstream and downstream of 

the isolated zone to record changes in concentration 

throughout the test. In this case, because the entry was not 

much larger than the vehicle itself, the vehicle acted like a 

piston within the isolated zone –flushing DPM 

downstream when traveling downwind and partially 

pulling DPM against the ventilation when traveling 
upwind. This type of cycling can be observed in figure 6, 

although the data shows some clipping due to the response 

times of the monitors. 

In this case, the DPM monitor indicated an average 

concentration of 180 ug/m3

 EC at the prevailing ventilation 

rate and a time-weighted average of 172 ug/m3

 EC over 

the testing period. The upstream measurements were 

below the limits of quantification of the instrument, and 

were therefore not corrected for. 

In order to make use of this data, the other vehicles in 

the fleet should be analyzed in a similar manner, and the 

contributions to DPM emissions compared proportionally. 

The time that a particular engine spends within the mine 

during a given shift and its location(s) as well as instances 

when the vehicle is idling all need to be factored into this 

analysis. Once this process is completed, vehicle emissions 

can be combated on a priority basis in order to enhance the 

effectiveness of DPM control strategies and potentially 

reduce implementation costs. 

2.3.2 Tailpipe monitoring for vehicle-specific emissions 

A proposed method for estimating vehicle-specific 

emissions is to perform tailpipe sampling of EC with the 

instruments. Although still under investigation, this type of 

testing would involve forcing engines into different 

operational modes and taking short samples of EC 

concentration from the exhaust exit. This would allow for 

an estimation of vehicle-specific contributions which is 

free from outside sources of DPM interference. In addition 

such a method may provide a beneficial approach towards 

monitoring changes in diesel particulate filter efficiencies 

over time and recognizing failures within the exhaust 

filtration systems. The difficulties involved in properly 

simulating transient loading cycles, removing water and 

temperature interferences, and accounting for leaks within 

the exhaust system as well as crankcase gas emissions are 

all areas of on-going research. 

2.3.3 Area sampling for vehicle-specific emissions 

A third, and fairly crude method for measuring vehicle 

specific contributions using the DPM monitors is to select 

a strategic location for area sampling throughout a shift 

and assess the fluctuations in real-time concentration over 

time. Matching the time-stamped data from the monitors 

with the times when an individual vehicle has passed the 

sampling location can provide a basic look at which 

vehicles are the largest emitters in that area of the mine. 

Although easier to perform than an isolated zone study, in 

terms of vehicle-specific emissions, this method may only 

useful to identify which vehicles are the major emitters of 

DPM in that area and is not practical for quantifying 

individual vehicle contributions. 

Figure 6 A real-time trace of recorded EC taken downstream during an isolated zone test. The chart shows concentration 

oscillations ascribed to the movement of the vehicle throughout the test. 

2.4 Measuring Miner-specific Exposure to DPM 

The DPM monitors are not recognized as an alternative to 

compliance sampling, but the instruments can be used in a 

similar manner to obtain an informative assessment of 

individual worker exposures. For compliance sampling, 

MSHA requires that a shift-weighted measurement of EC 

and TC exposure be taken (via the NIOSH 5040 method) 

from a mineworker’s breathing zone. To do this, a mine 

worker is outfitted with a sampling train consisting of a 

pump, flexible tubing and an integrated 

cyclone/impactor/filter assembly. The DPM monitors were 

designed to mimic this system and therefore use many of 

the same components. 

The monitors are capable of providing both shiftweighted EC and calculated TC exposures in real-time 

and, in addition, they can monitor changes in EC 

exposures throughout the entire shift. In some cases, it may 

be useful to ask the mineworker to record events that 

might affect DPM readings, such as times when the 

instrument was removed or unexpected changes in 

location. Coupling these records with the real-time values 

of EC and information on affective factors such as truck 

traffic, working conditions and ventilation rates can be 

useful when trying to pinpoint the cause of overexposures 

during a working shift. It is often the case that 

administrative controls can be implemented to limit these 

overexposures to DPM. 
2.5	 Measuring the Effectiveness of Cab Filtration 

Systems 

Environmental cabs can be an effective means for limiting 

mineworker exposure to DPM. However, simply leaving 

the window open or periodically opening the door can 

introduce enough DPM into the cab to cause an 

overexposure. Placing DPM monitors on the inside and 

outside of a cab throughout a shift can provide a relatively 

easy assessment of the effectiveness of the cab filtration 

system. 

In a previous study (Noll & Janisko, 2007), it was 

shown that this method can identify situations when a cab 

filtration system has failed, as well as identify occurrences 

where open windows or open doors are causing avoidable 

overexposures. In a properly functioning system, the 

monitor within the cab will indicate only small 

concentrations of EC throughout the shift, regardless of the 

exterior concentrations. An open door is characterized by a 

large spike in concentration that gradually falls to nearzero as DPM is flushed from the cab over time. A 

prolonged increase in DPM concentration within the cab 

that matches the exterior values is associated with 

instances where the cab window was left open. In some 

cases, simple administrative controls are all that are needed 

to remove these hazardous situations. 

3	 Conclusion 

This paper provides a practical approach to using real-time 

EC monitoring for the selection and evaluation of effective 

DPM controls. The ability to perform well-executed tests 

and to interpret the information that real-time monitors 

provide is an essential part of understanding the cause of 

DPM exposure. 

In particular, the information provided in charts of 

concentration changes over time is of great value. This 

data offers a novel way of understanding the factors that 

influence DPM exposure and drive concentration 

transients in an underground environment. In addition, it 

provides mine operators with a legitimate resource to aid 

in the reduction of DPM concentrations to meet the U.S. 

MSHA 2008 exposure limit of 160 ug/m3

 TC. 

It is the expectation of the authors that, as with all new 

technologies, a number of uses for these instruments have 

yet to be conceptualized. Therefore, the methods outlined 

in this paper should not be considered a comprehensive 

list, but rather as an initial guide to a number of novel 

techniques for assessing DPM concentrations in an 

underground environment. 

Disclaimer 

The findings and conclusions in this report are those of the 

authors and do not necessarily represent the views of the 

National Institute for Occupational Safety and Health. 

Mention of any product or company does not constitute 

an endorsement by NIOSH. 

References 

Birch, M.E. & Cary, R.A. (1996). Elemental carbon-based 

method for monitoring occupational exposures to particulate 

diesel exhaust, In Aerosol Sci. Technol., 25: 221-241. 

Birch, M.E. (2002). Occupational monitoring of particulate diesel 

exhaust by NIOSH method 5040, In Appl. Occup. Environ. 

Hyg., 17:400-405. 

Bugarski, A., Schnakenberg, G., Noll, J.D., Mischler, S., Crum, 

M. & Anderson, M. (2005). Evaluation of Diesel Particulate 

Filter Systems and Biodiesel Blends in an Underground 

Mine, In Transactions of the Society of Mining, Metallurgy, 

and Exploration; Society of Mining, Metallurgy and 

Exploration: Littleton, CO, vol. 318. 

Bugarski, A., Schnakenberg, G., Noll, J.D., Mischler, S., Patts, 

L., Hummer, J. & Vanderslice, S. (2003). Effectiveness of 

Selected Diesel Particulate Matter Control Technologies for 

Underground Mining Applications: Isolated Zone Study, 

CDC/NIOSH RI 9667; Centers for Disease Control, 

National Institute of Occupational Safety and Health: 

Washington, DC. 

Bugarski, A., Schnakenberg, G., Hummer, J., Cauda, E., Janisko, 

S. & Patts, L. (2007). Examination of Diesel Aftertreatment 

Systems at NIOSH Lake Lynn Laboratory. Proc. of the 

Mining Diesel Emissions Council (MDEC) Conference:, 

Richmond Hill, Ontario, Canada. 

Czerwinski, J., Peterman, J-L., Comte, P., Lemaire, J. & Mayer, 

A. (2007). Diesel NO/NO2/NOX Emissions - New 

Experiences and Challenges, SAE Technical paper 2007-01­

0321. 

Janisko, S. & Noll, J.D. (2008). Near-Real Time Monitoring of 

Diesel Particulate Matter in Underground Mines, Proc. 12th 

U.S./North American Mine Ventilation Symposium 2008, pp 

509-513, Taylor & Francis Group Plc. 

Mine Safety and Health Administration (MSHA) (2005). 30 CFR 

Part 57 Diesel Particulate Matter Exposure of Underground 

Metal and Nonmetal Miners; Final Rule. Fed. Reg. vol. 70, 

No. 107,32868. 

MSHA (2008), Enforcement of Diesel Particulate Matter Final 

Limit at Metal and Nonmetal Underground Mines, Program 

Policy Letter No. P08-IV-1. May 20, 2008. 

Noll, J., Bugarski, A., Patts, L., Mischler, S. & McWilliams, L. 

(2007), Relationship between Elemental Carbon, Total 

Carbon, and Diesel Particulate Matter in Several 

Underground Metal/Non-metal Mines. In Environ. Sci. and 

Technol., 41:710-716. 

Noll, J.D. & Janisko, S. (2007), Using laser absorption 

techniques to monitor diesel particulate matter exposure in 

underground stone mines. Proc. of SPIE, 8(47), vol 6759. 

McGinn, S., Grenier, M., Bugarski, A., Schnakenberg, G. & 

Petrie, D. (2002). Performance evaluation of diesel 

particulate filter technology in the underground 

environment, Proc. for the North American/Ninth US Mine 

Ventilation Symposium, Lisse, Netherlands: Balkema, pp 

433-440. 

Mogensen, G., Johansen, K. & Karlsson, H. (2009). Regulated 

and NO2 Emissions from a Euro 4 Passenger Car with 

Catalysed DPFs, SAE Technical Paper 2009-01-1083. 

United States Environmental Protection Agency (US EPA) 

(2007). The Cost-Effectiveness of Heavy-Duty Diesel 

Retrofits and Other Mobile Source Emission Reduction 

Projects and Programs, EPA420-B-07-006, May, 2007.