Real-Time DPM Ambient Monitoring in Underground Mines 

Hsin Wei Wu1,

1 Director, Gillies Wu Mining Technology, h.wu@minserve.com.au
 

A.D.S. Gillies2

,

2 Union Pacific/Rocky Mountain Energy Professor Missouri University of Science
 

and Technology, gilliesst@mst.edu
 

J. D Volkwein3

3 Research Physical Scientist, Pittsburgh Research Laboratories, National Institute of
 

Occupational Health and Safety, jdv1@cdc.gov
 

and J Noll4

4 Research Scientist, Pittsburgh Research Laboratories, National Institute of
 

Occupational Health and Safety, jin1@cdc.gov
 

ABSTRACT 

A real-time Diesel Particulate Matter (DPM) monitor has been developed on the 

basis of the successful National Institute of Occupational Health and Safety (NIOSH) 

designed Personal Dust Monitor (PDM) unit. The objectives of a recently completed 

Australian Coal Association Research Program (ACARP) study were to modify the 

PDM to measure the submicrometre fraction of the aerosol in a real-time monitoring 

underground instrument. Mine testing focused on use of the monitor in engineering 

evaluations to determine how conditions can be improved. Studies, including a 

selection during Longwall (LW) moves as described in this paper, demonstrated how 

DPM concentrations from vehicles fluctuate under varying ventilation and 

operational conditions. Correlation between the current SKC DPM measurement 

system and real-time DPM monitors were conducted and results from six mines show 

a correlation between elemental carbon (EC) and the new monitor DPM mass 

ranging from .51 to .81 with R2 >.90. These differences are suspected to be due to 

variations from mine to mine in aspects such as mine atmospheric contamination, 

vehicle fleet variations, fuel type, engine maintenance, engine combustion efficiency, 

engine behaviour or interference from other submicrometre aerosol..Real-time 

monitoring readily reflects the movement of individual diesel vehicles and allows 

pin-pointing of high exposure zones such as those encountered where various 

vehicles work in areas of constrained or difficult ventilation. DPM monitoring 

approaches that have been available for some time based on shift average monitoring 

do not readily allow successful engineering evaluation exercises to determine 

acceptability of pollution levels. Identification of high DPM concentration zones 

allows efficient modification of mine ventilation, operator positioning and other work 

practices to reduce miners’ exposures without waiting for laboratory analysis results. 

1 
INTRODUCTION 

The real-time DPM monitor has been developed on the basis of the successful PDM 

unit for respirable dust monitoring. The objectives of recently completed ACARP 

study (Gillies and Wu, 2008) has been to finalise the design of a DPM unit, to 

undertake comprehensive and internationally recognised laboratory testing, to 

evaluate the new design, and to undertake an underground series of tests to establish 

the robustness and reliability of the new approach. 

The PDM gives real-time readings and is mounted within the miner’s cap lamp 

battery and internally measures the true particle mass of aerosol collected on its filter. 

Measurements are insensitive to water spray as opposed optically based measurement 

approaches. It has been recognised that the PDM’s unique measurement approach has 

application to allow real-time atmospheric DPM monitoring. The industry has no 

real-time direct reading atmospheric DPM monitor at present. Under the project 

Thermo Fisher Scientific has undertaken structural changes to the PDM to convert it 

to a DPM real-time monitoring underground instrument, the D-PDM. The 

Pennsylvania Pittsburgh Research Laboratories of NIOSH (the group that originally 

contracted for the PDM development) has undertaken laboratory “calibration or 

verification” testing. A phase of Australian mine robustness and engineering testing 

has been undertaken to ensure the instrument can effectively assist mine management 

to help handle this health issue. 

Tests have been undertaken at points of expected high atmospheric DPM such as 

during LW face moves and in Development Headings. The paper discusses how the 

monitors have performed within the underground mine environment in evaluating 

DPM during the various phases of LW moves. The project has closely examined the 

influence of aspects of the mine ventilation system. Results have been compared to 

alternative industry pollutant measuring approaches. The outcomes of the project 

demonstrate a new tool for understanding the atmosphere in the presence of DPM. 

DEVELOPMENT OF REAL-TIME PERSONAL DIESEL PARTICULATE
 

MONITOR
 

Mine atmosphere measurements of DPM in Australian mines have been measured 

systematically since the early 2000s. Most initial atmospheric readings have been 

taken on a shift average basis using SKC sampling units. The SKC is derived from a 

US NIOSH design and gives readings in the surrogate Total Carbon (TC) or 

Elemental Carbon (EC) units after laboratory analysis procedures have been 

completed. 

• DPM = TC + inorganics = EC + organic carbon (OC) + inorganics 

2 
• TC in mine testing is generally 80% of DPM (Volkwein 2006). 

Some DPM regulatory guidelines are starting to emerge in Australia and the 

individual states are generally moving to acknowledge DPM limits of 0.2 mg/m3 

submicrometre particulate matter, 0.16 mg/m3 TC particulate and 0.1 mg/m3 EC 

particulate. A few prescriptive mining regulations are in force internationally such as 

those applying to the US metalliferous mining industry from May 2008 based on a 

DPM limit of 0.16 mg/m3 TC particulate. The real-time DPM monitor is being 

developed on the basis of the successful PDM unit. Thermo Fisher Scientific has 

undertaken structural changes to the PDM to convert it to a submicrometre real-time 

monitoring underground instrument, the D-PDM. The Pittsburgh Research 

Laboratories of NIOSH (the group that originally contracted for the PDM 

development) has undertaken laboratory evaluation of the concept. The real time 

DPM unit continually reports levels of mine atmosphere submicrometre aerosol in 

mg/m3 from real-time readings. 

The submicrometre size-selective inlet selected for this potential field instrument was 

the BGI 1-μm sharp-cut cyclone model SCC0.732 followed by a Bureau of Mines 

(BOM) designed 0.8 micrometre cut point impactor, at a flow rate of 1.7 lpm. 

Figure 1 shows the size selective configuration. 

 

 

 

BOM, 0.8 um impactor BGI cyclone 

DPM and mine dust are pulled 

into the BGI Cyclone Inlet. 

Figure 1 Schematic of prototype D-PDM Sampling Inlet. 

The D-PDM instrument is currently at a prototype stage and as with all new 

technologies will need industry acceptance and support to reach its full potential. 

MONITORING OF DIESEL PARTICULATE MATTER 

The mine tests by their very nature were restricted to equipment available for testing 

underground. Six of the mines visited (Mines A to F) focused on LW equipment 

moves from one panel to another and particularly examined the various ventilation 

arrangements used during shield transport to the installation roadway. The real-time 

DPM monitors successfully evaluated changes during the different tests and between 

different steps within the individual tests. 

3 
Mine A 

Mine A testing found it was straight forward to analyse results for arrival and 

departure times of diesel machines at the face and see whether these matched the 

arrival of the vehicle exhaust plume. Figure 2 examines one three hour period record 

of real-time DPM readings as compared to heading air velocity and shield carrier 

speed. 

 

 

 

 

0

0.5

1

1.5

2

2.5

3

 

DPM Survey of LW Chock Move Activity 

Measured Downstream of MG Travel Road 

7:20 7:40 8:00 8:20 8:40 9:00 9:20 9:40 10:00 10:20 

Time (minutes) 

D-PDM Conc. (mg/m3 ) 

#108 10mins #108 30mins 

Chock Carriers 

Arriving Face 

#130-23 

#1112 #1113 #130-24 

Figure 2 Observations on shield carrier DPM over a three hour period at monitor 108 

fixed location. 

Close examination of results from #108 monitoring the DPM downstream of 

the main gate (MG) and back road showed that when the shield carriers travel in that 

in three cases they arrived at the tail gate (TG) end of the face in advance of the peak 

level of the DPM cloud. This indicated that the carriers were generally travelling at 

higher average speed than the air velocity. However Carrier #1112 arrived slightly 

later indicating slower machine travel speed than air velocity. The time difference 

and the peak concentration depend on the air velocity and shield carriers’ travel 

speeds. Put simply if the shield carrier travels at the same speed as air velocity peak 

concentration will be extremely high and the carrier will arrive at the same time as 

the peak. Note that the DPM data has a lag time because it is presented as a rolling 

average concentration over the previous 10 minutes or 30 minutes. 

Mine B 

Mine B completed an audit on sources of DPM within a LW installation panel by 

strategically placing the real-time DPM monitors at points as shown in Table 1. DPM 

make values account for DPM monitored value in air mg/m3

) and air quantity 

diluting the exhaust (m3

/s). These values (mg/s) give a value that can be compared 

for different equipment under varying ventilation and other mine conditions. 

4 
Table 1 Sources of DPM identified in the installation LW panel in Mine B. 

 Location Sources (μg/s) % Comments 

 MGC&DHdgs 3.03 18.6 Mains air at MG entrance 

 Borehole 0.00 0.0 back of LW panel, fresh air 

 LWFace4.77 29.2 Shunting Mule or LHDs 

 TGDHdg6.96 42.6 Shield carriers travel way 

 TGCHdg0.00 0.0 No diesel activity 

 Leakages 1.57 9.6 Mains air; coffin seal & double doors 

 Measured Total 16.32 100.0 

Mine C 

Mine C examined one 2.5 hour period as a 37 tonne Dozer was brought in to pull the 

first shield on recovery a LW face as shown in Figure 3.

 

 

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

 

 

 

 

 

 

 

 

 

 

 

 

 

DPM Survey at LW Move Activity Day 2 2007 

14:40 14:50 15:00 15:10 15:20 15:30 15:40 15:50 16:00 

Time (minutes) 

D-PDM Conc. (mg/m3 ) 

#106 

#108 

#110 

On Dozer 3504 

LW Chock 163 (Outbye) 

TG B Hdg 8-9ct (Inbye) 

Dozer pulling Chock 172 

#106 D-PDM - 0.050 mg/m3 

#108 D-PDM - 0.072 mg/m3 

#110 D-PDM - 0.233 mg/m3 

DPM Make = 8.20 mg/s 

Dozer & Chock Chariot pulling 

Chock 172 

#106 D-PDM - 0.137 mg/m3 

#108 D-PDM - 0.135 mg/m3 

#110 D-PDM - 0.790 mg/m3 

DPM Make = 33.43 mg/s 

Figure 3 Submicrometre DPM in LW Recovery Face Pulling Shield. 

About 51 m3

/s of air was 

measured on the LW recovery face. Between 14:45 and 15:32, the Dozer attempted 

to pull out the first shield but was unsuccessful. It worked hard much of the time at 

maximum revs. Between 15:32 and 16:00, a Shield Carrier Chariot was chained to 

the Dozer and together they successfully pulled the first Shield while working hard. 

A general observation on LW moves was that some high submicrometre aerosol 

readings were recorded due to the large numbers of diesel activities in working 

sections of the mine. This was contributed to by frequent vehicle movements or 

traffic jams. Miners should not be placed working inbye heavy vehicles working very 

hard such as the dozer when pulling shields. For the LW Move routes it is best if 

vehicle travels against airflow direction. 

5 
Mine D 

Mine D monitored a highwall mine with no underground Mains headings. Ventilation 

quantity was high and air entered the panel in a clean state. It was found over a 

number of tests that 62% of DPM within the panel was generated by Carriers hauling 

Shields in the gateroads and 38% generated by vehicle movement along the LW face. 

Air passing down the segregated belt gateroad reached the face clean and could have 

been used to better effect on the face where operators were installing newly arrived 

shields. When planning LW moves mines should evaluate and review alternatives for 

ventilating shield travel roads to the face. The DPM plots in Figure 4 show variability 

with the Dozer working as four shields were installed. The difference between LW 

MG and TG plots clearly shows contributions of the face Dozer.. 

 

 

0

0.2

0.4

0.6

0.8

1

 

 

 

 

 

 

 

 

DPM Survey at LW Move Activity 

12:30 13:00 13:30 14:00 14:30 15:00 15:30 16:00 16:30 17:00 

Time (minutes) 

D-PDM Conc. (mg/m3 ) 

#110 at LW MG end #108 at LW TG Inbye Installation 

Showing when Dozer working inbye of MG monitoring point 

Time TG MG Difference Dozer DPM Comments 

mg/m3 mg/m3 mg/m3 mg/s 

12:35-13:08 0.179 0.074 0.105 5.24 Full cycle 

13:40-14:02 0.132 0.034 0.098 4.89 Full cycle 

14:34-15:13 0.181 0.086 0.095 4.78 Full cycle 

16:45-17:00 0.219 0.059 0.160 8.01 Half cycle 

Figure 4 DPM in Mine D LW Installation Face outbye/inbye the face working dozer 

Mine E 

Mine E tests on the recovery face were in a well ventilated situation with clean 

gateroad belt heading air significantly diluting any DPM pollution from the gateroad 

travel heading. An electric tracked “mule” moved Shields along the face and did not 

add DPM pollution. Figure 5 shows influence of DPM make at the installation face 

with outbye monitored levels subtracted. The close match between times chariots’ 

face time and DPM pollution levels inbye can clearly be seen. General 

recommendations were in a planning a LW move it is advantageous to evaluate and 

6 
review all alternatives for ventilating Shield travel roads to or from the LW recovery 

and installation faces to reduce peak and average miner exposures. 

0

0.2

0.4

0.6

0.8

1

1.2

1.4

 

 

 

 

DPM Survey at LW Move Activity 

9:30 10:00 10:30 11:00 11:30 12:00 12:30 13:00 13:30 14:00 14:30 15:00 

Time (minutes) 

D-PDM Conc. (mg/m3 ) 

CC 

1307 

CC 

1325 

CC 

1307 

CC 

1307 

CC 

1307 

CC 

1307 

CC 

1307 

Showing chock chariot arriving, loading chock 

and departing 

Difference in DPM readings between #108 and #110 

Figure 5 Difference in outbye and inbye DPM in Mine E LW Installation Face 

Mine F 

Figure 6 shows the influence of DPM make from diesel activities at a LW face with 

outbye monitored levels subtracted. 

Mine F DPM Survey at LW Move Activity 02/09 

Difference in DPM readings between LW Chock 75 (#106) and Chock 18 (#110) 

Chariot Loader into face 

drop to reposition Chariot Loader into face to 4.0 chock chock drop reposition chock Chariot Loader into face 

chock drop to reposition 

3.5 chock chock 

) 3 m/

3.0

gm(

2.5

. cn

2.0

oC M 

1.5

DP1.0

D 0.5

0.0 

0:00 1:00 2:00 3:00 4:00 5:00 

Time (minutes) 

Figure 6 DPM and diesel activities in Mine F LW Installation Face 

The close match between time the chariots and 

7 
loader were operating in the face and monitored pollution levels inbye is clearly seen. 

An audit was completed on sources of DPM within the LW installation panel by 

strategic placement of the DPM monitors. It was found that 25% was contributed 

from outbye diesel activities in Mains, 25% from diesel activities in panel the Travel 

Road, and 50% from diesel activities within face areas. A good initiative in this mine 

has been to limit the number of vehicles in the panel by the use of a Tag Board and 

Traffic controller at the panel travel road entrance. The diesel Tag Board design 

should consider the diesel loading from outbye Mains diesel activities which account 

for up to 25% of the total diesel loading for the LW panel. Summary of DPM levels 

from each shift at points monitored throughout the panel showed increasing levels 

from influence of additional equipment in series within the ventilation circuit. 

SKC MINE COMPARISON TESTS 

It is appropriate to compare field results from the real-time DPM monitor with 

another available measuring instrument .the NIOSH developed SKC impactor 

system. The SKC system delivers laboratory analysed shift average results and not 

real-time results. During investigations parallel underground SKC samples have been 

taken for comparison with the real-time DPM monitored results. These samples came 

from the same mine atmosphere through use of a “can” with outlets for real-time 

DPM and SKC monitors. Under the SKC system the sample submicrometre fraction 

is deposited on a filter after first passing through a respirable cyclone sampler and a 

0.8 micrometre impactor that removes most of the mineral fraction of the sample. 

The sample filter is analysed for EC and (Organic Carbon) OC whose sum is the TC. 

8 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mine B 

EC = 0.816*Submicron 

Submicron = 1.226*EC 

R2 = 0.98 

Mine A 

EC = 0.645*Submicron 

Submicron = 1.550*EC 

R2 = 0.97 

Mine C 

EC = 0.510*Submircron 

Submicron = 1.961*EC 

R2 = 0.90 

Mine D 

EC = 0.450*Submicron 

Submicron = 2.222*EC 

R2 = 0.75 

Mine E 

EC = 0.788*Submicron 

Submicron = 1.269*EC 

R2 = 0.97 

Mine F 

EC = 0.683*Submicron 

Submicron = 1.462*EC 

R2 = 0.98 

0.0 

0.2 

0.4 

0.6 

0.8 

1.0 

1.2 

0.0 0.2 0.4 0.6 0.8 1.0 1.2 

EC Conc. (mg/m3

) 

D-PDM Conc. (mg/m3) 

Mine F 

Figure 7 Mine individual relationships between EC and Submicrometre DPM 
Figures 7 and 8 show a related set of results, namely those from Mines A to F LW 

moves..Real-time DPM results (designated as D-PDM measurements) are compared 

with shift average SKC impactor determinations of EC and TC particulate. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mine A 

TC = 0.865*Subm icron 

Subm icron = 1.156*TC 

R2 = 0.99 

Mine B 

TC = 0.968*Submicron 

Subm icron = 1.033*TC 

R2 = 0.99 

Mine C 

TC = 0.743*Submicron 

Submicron = 1.345*TC 

R2 = 0.99 

Mine D 

TC = 0.885*Submicron 

Submicron = 1.130*TC 

R2 = 0.98 

Mine E 

TC = 1.082*Submicron 

Subm icron = 0.924*TC 

R2 = 0.98 

Mine F 

TC = 0.827*Subm icron 

Subm icron = 1.209*TC 

R2 = 0.97 

0.0 

0.2 

0.4 

0.6 

0.8 

1.0 

1.2 

0.0 0.2 0.4 0.6 0.8 1.0 1.2 

TC Conc. (mg/m3

) 

D-PDM Conc. (mg/m3 ) 

Mine F 

Figure 8 Mine individual relationships between TC and Submicrometre DPM 

Close 

correlations were found for all cases (R2 ≥0.97) for TC versus DPM. All EC versus 

DPM correlations were good (R2 ≥0.90) except for one set of mine results. The 

results also demonstrate that relationships (the slopes of the individual mine 

relationships) vary between mines. This differences in suspected to be due to 

variations between mines in aspects such as atmospheric contamination, vehicle fleet 

variations, fuel type, engine maintenance, engine combustion efficiency, engine 

behaviour, or interference from other submicrometre aerosol. 

9 

 

 

 

 

 

EC vs DPDM regression 

1.4 

DPDM conc (mg/m3) 1.2 

1.0 

0.8 

0.6 

0.4 

0.2 

0.0 

y = 1.21x + 0.04 

R2 = 0.97 

95% Prediction 

Intervals 

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 

EC conc. (mg/m3) 

Figure 9 Combined relationships for Six mines between EC and Submicron DPM. 
Figure 9 shows combined DPM results from the all mine test series compared with 

SKC impactor collection determinations of EC particulate shift average results taken 

in the particular mine at the same time. The distribution shows the calculated upper 

and lower 95% confidence limits about the regression. The combined mines 

relationships are close with R2 = 0.97 for EC compared with submicron DPM. 

There is some international debate on the DPM monitoring issue of whether 

submicrometre diesel particulate (DP), TC or EC should be evaluated. The real-time 

DPM monitor is the only one measuring submicrometre DP. Various international 

studies show that in the normal mine atmosphere (with moderate loadings of 

respirable dust below statutory limits) the differences and the potential levels of error 

between the three approaches for monitoring DPM are relatively minor (Birch and 

Cary, 1996, Birch and Noll, 2004 and Dabill, 2005). 

CONCLUSIONS 

A project on diesel particulate matter real-time monitoring has been discussed. The 

outcome is that objective testing over different approaches and comparisons with the 

SKC monitoring lead to the conclusion that this real-time DPM unit provides 

reasonable results. The principal industrial application of the unit will be to give a 

greater understanding through real-time information of DPM levels in mine 

environments and particularly in engineering evaluation exercises. The paper has 

discussed how the monitor has performed within the underground mine environment 

in evaluations of LW moves and has closely examined the influence of aspects of the 

mine ventilation system on underground DPM pollution. 

 REFERENCES 

Birch, M.E. and Cary, R.A., 1996. Elemental Carbon-based Method for Monitoring 

Occupational Exposures to Particulate Diesel Exhaust. Aerosol Science and 

Technology 25: 221-241. 

Birch, M.E. and Noll, J.D., 2004. Submicrometre Elemental Carbon as a Selective 

Measure of Diesel Particulate Matter in Coal Mines. J Environ Monit. 2004, 6: 

799-806. 

Dabill, D. W., 2005. Controlling and monitoring exposure to diesel engine exhaust 

emissions in coal mines, Report HSL/2005/55, Health and Safety Laboratory, 

Buxton, England 

Gillies, A.D.S and Wu, H.W. 2008. Evaluation of a first mine real-time diesel 

particulate matter (DPM) monitor, Australian Coal Association Research Program 

Grant C15028, Final Report, April. 

Volkwein, J.C., 2006. Technology Transfer Workshop - Better Use of Diesels 

Underground, Mackay 22 September and Belmont 26 September 2006. 

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