TM

RI 9669 

REPORT OF INVESTIGATIONS/2006 

Laboratory and Field Performance 

of a Continuously Measuring Personal 

Respirable Dust Monitor 

Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health
 

Report of Investigations 9669 

Laboratory and Field Performance of a Continuously Measuring 

Personal Respirable Dust Monitor 

By Jon C. Volkwein, Robert P. Vinson, Steven J. Page, Linda J. McWilliams, 

Gerald J. Joy, Steven E. Mischler, and Donald P. Tuchman 

DEPARTMENT OF HEALTH AND HUMAN SERVICES 

Centers for Disease Control and Prevention 

National Institute for Occupational Safety and Health
 

Pittsburgh Research Laboratory 

Pittsburgh, PA 

September 2006 
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 Web site: www.cdc.gov/niosh 

 

 

The findings and conclusions in this report have not been formally disseminated by the 

National Institute for Occupational Safety and Health and should not be construed to 

represent any agency determination or policy. 

————————————————————— 

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

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

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

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

DHHS (NIOSH) Publication No. 2006–145 
CONTENTS
 Page 

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

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

Description of the PDM.................................................................................................................................................3 

 System configuration...............................................................................................................................................4 

 Sample flow path.....................................................................................................................................................5 

 Flow measurement and control................................................................................................................................6 

 Battery configuration...............................................................................................................................................6 

 Data treatment..........................................................................................................................................................7 

 TEOM mass measurement technique ......................................................................................................................7 

 Momentum compensation: the key to miniaturization ...........................................................................................8 

Methods .........................................................................................................................................................................8 

 Laboratory methods.................................................................................................................................................8 

 Dust exposure chamber ...................................................................................................................................9 

 Samplers..........................................................................................................................................................9 

 PDM......................................................................................................................9 

 Gravimetric reference..............................................................................................................................10 

 Impactors..............................................................................................................10 

 Analytical gravimetric precision ...................................................................................................................11 

 Experimental design......................................................................................................................................11 

 PDM battery test............................................................................................................................................12 

PDM mass constant verification....................................................................................................................13 

 Definition of constant..............................................................................................................................13 

 Procedure to determine mass constant.....................................................................................................13 

Analysis........................................................................................................................................................14 

 Detailed in-mine test methods...............................................................................................................................15 

Criteria for mine selection.............................................................................................................................15 

 Detailed mine procedures..............................................................................................................................15 

 Area sampling ...............................................................................................................................................17 

 Maintenance and use log ...............................................................................................................................17 

 Field precision analysis .................................................................................................................................17 

Results .........................................................................................................................................................................18 

 Laboratory accuracy verification...........................................................................................................................18 

 Premine testing..............................................................................................................................................18 

 Postmine testing ............................................................................................................................................19 

Accuracy .......................................................................................................................................................20 

 Calibration constant K0.................................................................................................................................21 

Limit of detection and quantification ............................................................................................................22 

 Battery depletion effects................................................................................................................................23 

 Detailed in-mine testing.........................................................................................................................................24 

 Performance over project duration ................................................................................................................24 

 Extended testing ............................................................................................................................................25 

 Maintenance results.......................................................................................................................................25 

 Underground precision..................................................................................................................................27 

Discussion....................................................................................................................................................................28 

 Instrument bias ......................................................................................................................................................28 

 Precision ................................................................................................................................................................29 

 Training and comments .........................................................................................................................................29 

 Screen presentation of data....................................................................................................................................30 

 Performance issues ................................................................................................................................................31 

 

 
 

 Data files................................................................................................................................................................32 

 Download ......................................................................................................................................................32 

 Interpretation .................................................................................................................................................34 

 Error codes.............................................................................................................................................................34 

 Meaning and interpretation..............................................................................................................................34 

 Distinguishing valid data .................................................................................................................................35 

 Maintenance ..........................................................................................................................................................36 

 Calibration .............................................................................................................................................................37 

 Flow...........................................................................................................................37 

 Mass..........................................................................................................................38 

Conclusion...................................................................................................................................................................38 

Acknowledgments .......................................................................................................................................................39 

References ...................................................................................................................................................................40 

Appendix A.—Detailed mine PDM concentration data ..............................................................................................42 

Appendix B.—Detailed mine Lippmann sampler data................................................................................................44 

Appendix C.—Analysis of voided respirable coal mine dust samples collected, 1995–2004.....................................46 

ILLUSTRATIONS

 1. PDM internal components......................................................................................................................................4 

2. Precommercial PDM connected to white docking station used for charging and communication with a PC
 

 using an RS–232 interface ...................................................................................................................................5 

3. Technician changing filter on the PDM mass sensor using a custom-supplied filter tool ......................................6 

4. Laboratory test chamber and arrangement of instruments....................................................................................11 

5. Battery testing to failure using flow rate as an indicator ......................................................................................23 

6. Basic PDM screen display formats and information presented ............................................................................31 

7. Example of data printout ......................................................................................................................................33 

8. Detail of results from sample shown in figure 7...................................................................................................34 

9. Mass offset "error" resulting from pinched tube and subsequent recovery of correct mass measurements..........36 

TABLES

 1. Detailed mine characteristics and location of Lippmann sample..........................................................................15 

2. Premine laboratory data of reference mass measurements and PDM mass measurements ..................................19 

3. Postmine laboratory data of references mass measurements and PDM mass measurements ...............................20 

4. PDM pre- and postmine lab accuracy calculations...............................................................................................21 

5. Comparison of PDM measured K0 and programmed K0 .....................................................................................22 

 6. 	 Total samples taken during detailed mine sampling and number of valid samples when NIOSH was
 

 present or absent from the mine property ..........................................................................................................24 

7. Summary of PDM use and repair by quintile .......................................................................................................26 

8. Overall success rate by quintile ............................................................................................................................27 

9. Field precision results...........................................................................................................................................28 

10. PDM performance issues and comments..............................................................................................................32 

11. Flow calibration history........................................................................................................................................37 
 CL 

ACRONYMS AND ABBREVIATIONS USED IN THIS REPORT
 

ANOVA analysis of variance 

BMRC British Medical Research Council 

 confidence limit 

CMDPSU coal mine dust personal sampler unit 

DO Dorr-Oliver

 EOS end of shift 

GSD geometric standard deviation 

HD Higgins-Dewell 

HEPA high-efficiency particulate air 

ISO International Organization for Standardization 

LED light-emitting diode 

LOQ limit of quantification 

MMAD mass median aerodynamic diameter 

MO mass offset 

MRE Mining Research Establishment (U.K.) 

MSHA Mine Safety and Health Administration 

NIOSH National Institute for Occupational Safety and Health 

PDM personal dust monitor 

PEL permissible exposure limit 

PRL Pittsburgh Research Laboratory (NIOSH) 

PVC polyvinyl chloride 

RH relative humidity 

RMSE root mean square error 

RSD relative standard deviation 

TE tapered element 

TEC Thermo Electron Corp. (Albany, NY) 

TEOM tapered-element oscillating microbalance 

UCL upper confidence limit 
UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT

 hr hour 

 in inch

 kg kilogram

 L/min liter per minute 

lb pound 

mg milligram

 mg/m3  milligram per cubic meter 

 min minute

 mm millimeter 

 mm Hg millimeter of mercury 

sec second 

 μg microgram

 μm micrometer 

 EC degree Celsius 

 EF degree Fahrenheit 
 

LABORATORY AND FIELD PERFORMANCE 

OF A CONTINUOUSLY MEASURING 

PERSONAL RESPIRABLE DUST MONITOR 

By Jon C. Volkwein,1

1

Research physical scientist.

 Robert P. Vinson,2

2

Physicist. 

Steven J. Page,3

3

Research physicist. 

Linda J. McWilliams,4
 

4

Statistician.
 

Gerald J. Joy,5 Donald P. Tuchman5
 

5

Industrial hygienist.

Steven E. Mischler, and 6

6

Physical scientist. 

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

ABSTRACT 

The National Institute for Occupational Safety and Health (NIOSH), through an informal 

partnership with industry, labor, and the Mine Safety and Health Administration, has developed 

and tested a new type of instrument known as the personal dust monitor (PDM). The dust 

monitor is an integral part of the cap lamp that a miner normally carries to work and provides 

continuous information about the amount of respirable coal mine dust in the breathing zone of 

that individual. Testing was conducted on 25 prototype instruments in the laboratory to verify 

the instruments’ accuracy as received from the manufacturer and after a period of underground 

use. The laboratory testing verified previous work; there is a 95% confidence that the individual 

PDM measurements were within ±25% of reference measurements. In-mine testing determined 

the precision, durability, and miner acceptance. Data from the mines showed a field precision of 

0.078% relative standard deviation for the PDM and 0.052% for the recognized standard— 

the coal mine dust personal sampler unit. The PDM had about 90% availability for collecting 

valid information in over 8,000 hr of underground use. Anecdotal comments by miners indicated 

that they found the PDM more convenient to wear for sampling than currently used instruments 

because of the integration of the sampler into the normally worn cap lamp. The means of the 

instruments’ pre- and postmine accuracy verification test values were statistically equivalent. 

Additional data were collected to measure the equivalency of the PDM to the U.K. Mining 

Research Establishment sampler, as required by U.S. law. However, analysis of the data was 

more complex than originally anticipated because the variance with increasing concentration 

required use of a more sophisticated statistical model. Explanation of and results from this work 

will be the subject of a second publication. Under the broad range of test conditions covered in 

this work, the PDM functioned as well as the current sampler in terms of availability for use, 

accuracy, precision, and miner acceptance. 
INTRODUCTION 

Measurement of workplace dust is an essential first step in eliminating lung disease caused by 

overexposure to dust. The Federal Coal Mine Health and Safety Act of 1969, the predecessor 

to the Federal Mine Safety and Health Act of 1977, mandates that coal mine dust levels be 

monitored and controlled to at or below 2 mg/m3

 for a shift. To date, this monitoring process has 

relied upon a coal mine dust personal sampler unit (CMDPSU) to collect a filter sample in the 

mine environment. The respirable dust-laden filter is then sent to a laboratory for analysis. 

Results are returned to the mine operators several days or occasionally weeks after the actual 

samples were taken. Following a long history of developmental efforts associated with lightscattering [Williams and Timko 1984], fixed-site, and personal continuous dust monitors [Kissell 

and Sacks 2002], the Secretary of Labor and the Federal Advisory Committee on the Elimination 

of Pneumoconiosis Among Coal Mine Workers [U.S. Department of Labor 1996] directed the 

National Institute for Occupational Safety and Health (NIOSH) to embark on research to 

improve sampling instrumentation for use in the mining industry. In consultation with labor, 

industry, and government, NIOSH issued a contract (CDC contract 200–98–8004) to Rupprecht 

and Patashnick Co., Inc. (now Thermo Electron Corp. (TEC)), Albany, NY, to develop a 

personal dust monitor (PDM). The PDM is based on an environmental ambient air monitor that 

has achieved global acceptance for use in air quality monitoring networks. The important aspect 

of this monitor is that it directly measures the mass of dust on a filter regardless of dust 

composition, size, or physical characteristics. This contract work successfully miniaturized the 

air quality monitor’s sensor and incorporated the sensor into a prototype person-wearable dust 

monitor that provided accurate end-of-shift (EOS) data [Volkwein et al. 2004]. Laboratory 

results from this work demonstrated that with different coal types and size distributions there was 

a 95% confidence that the individual PDM measurements were within ±25% of reference 

measurements. Mine test results comparing the PDM prototype with adjacent reference samplers 

indicated that the measurements were statistically indistinguishable. In mines, the technology 

proved durable enough to successfully measure 108 shifts of data out of 115 attempts in the 

mines. Under these specific test conditions, the PDM was shown to be convenient to wear and 

robust to use, provided accurate and timely data that could be used to monitor and prevent 

overexposure, and was easy to use. 

Encouraged by the promising results from the initial laboratory and in-mine tests of the prototype 

PDM, the Mine Safety and Health Administration (MSHA) announced in June 2003 that it 

would suspend all work to finalize the proposed dust rules published in March 2003 and pursue 

accelerated research on the PDM [MSHA 2003]. In addition, the other PDM development 

partners, consisting of labor and industry, contributed toward drafting a test protocol to 

determine if the PDM was in fact suitable for use in coal mines, durable for everyday mine use, 

and ergonomically acceptable to miners. Another part of the protocol required measuring 

precommercial PDM performance in the laboratory and in mine environments for accuracy, 

precision, functionality, and long-term performance. 

This report includes the first two of three major areas studied. The first is a confirmation that the 

laboratory accuracy of the precommercial PDM is similar to that of the prototype instrument and 

that the accuracy is maintained after in-mine use of the instrument. The second area is a detailed 

underground evaluation that includes measurement of the precision of the PDM, the CMDPSU, 

2
 
and the impactor to be used to measure the dust size distribution. The detailed underground 

evaluation also determines the performance of the PDM while in routine use by miners. 

The third area of this testing—to determine the equivalency of the PDM to standards of the 

U.K. Mining Research Establishment (MRE) and the International Organization for 

Standardization (ISO) for underground mines—is more complex than originally anticipated and 

will require use of a more sophisticated statistical model than originally planned. To proceed 

with the finished portion of this work, NIOSH has elected to present this work in a second 

publication. 

Quantifying the fraction of dust that is considered respirable is an important part of measuring a 

worker’s risk from dust. The ISO [1995] has recommended that the definition of respirable dust 

follow the convention described by Soderholm [1989]. Because no device precisely follows this 

theoretical convention, specific size classification devices that are used exhibit inherent bias 

when attempting to duplicate the convention. In fact, the 10-mm Dorr-Oliver (DO) dust cyclone 

currently used in the CMDPSU has bias relative to both the ISO and the British Medical 

Research Council (BMRC) definition of respirable dust [Bartley et al. 1994]. The BMRC 

definition was adopted by the MRE as the convention used to relate dust concentrations to 

worker health effects. The cyclone chosen for use in the PDM required a configuration that 

could accept a tube originating at the hard hat inlet. The cyclone selected followed the HigginsDewell (HD) design previously shown through testing to have low bias relative to the ISO 

convention [Maynard and Kenny 1995]. 

This report presents the theory of operation, description, performance of the PDM compared to 

gravimetric-based reference dust sampling methods, and functionality of the instrument when 

used by miners. It specifically addresses the accuracy of the instrument before and after mine 

testing and the in-mine precision. 

DESCRIPTION OF THE PDM 

The dust monitor described in this report is a precommercial (not for general sale) Model 3600 

PDM that functions identically to a prototype monitor originally developed under contract. 

This PDM differs from the prototype in that it incorporates a stronger case, improved display, 

more efficient power management, and improved software. The device is intended to be 

virtually “invisible” to the miner as a replacement for the cap lamp and battery currently used 

in most mines. 

The tapered-element oscillating microbalance (TEOM) mass sensor was the key to the accurate, 

time-resolved measurements provided by the PDM [Patashnick and Rupprecht 1991]. TEC has 

applied this mass measurement technique to a variety of arenas requiring time-resolved 

measurements, including ambient air, diesel, and stack particulate monitoring. This inertial, 

gravimetric-equivalent, mass measurement technique typically provides a limit of detection 

equivalent to that of the most sensitive laboratory-based microbalances. The development of the 

TEOM technique for use in a small personal exposure monitor, subjected to the harsh conditions 

of an underground mine, brought new challenges. As a result of a multiyear effort, TEC 

invented a hardware-based momentum compensating approach that effectively isolated the mass 

monitor from external shocks and was essential to providing microgram mass resolution in 

challenging applications. 

3
 
 

4
 

System Configuration 

The PDM is a combined respirable dust sampler and cap lamp configured to have dimensions 

and weight similar to those of a current lead-acid-type miner’s cap lamp battery. Components of 

the device include a sample inlet tube, HD cyclone, air heater, pump, dust sensor, sampler 

battery, cap lamp battery, electronic control and memory boards, a display screen, and 

Windows®-based computer interface software called WinPDM. Figure 1 shows some of these 

components. The PDM case is hardened to withstand the harsh conditions found in the mine 

environment, with the system designed to meet MSHA drop test requirements for cap lamps 

(30 CFR7

7

Code of Federal Regulations. See CFR in references. 

19) as well as intrinsic safety-type approval requirements (30 CFR 18). 

 

Display 

and Buttons Power Takeoff 

Block with 

Flow Sensor Orifice 

Temp and RH 

Cap Lamp 

Cyclone 

TEOM 

Mass Sensor 

Air heater 

Sample filter 

Pump 

Sample Air/Electrical Inlet 

Umbilical Cable 

Cap Lamp 

Battery (Left) 

TEOM System 

Battery (Right) 

 

Figure 1.—PDM internal components. 

 The PDM 

system also includes a nonintrinsically safe docking station that is simultaneously used to 

communicate with personal computer software for programming and retrieving stored data in 

the instrument and to recharge its batteries for the next work shift (Figure 2). 
 

 

 Figure 2.—Precommercial PDM connected to white docking station (left) used for 

charging and communication with a PC using an RS–232 interface. 

Sample Flow Path 

A 2.2-L/min flow of particle-laden air from the mine atmosphere enters an inlet adjacent to the 

cap lamp, mounted on the bill of the miner’s hard hat, and passes through flexible conductive 

tubing before reaching the HD cyclone at the entrance of the PDM. The cyclone separates the 

dust, allowing particles that could penetrate to the lung (respirable dust) to proceed through a 

heated section of tubing to remove excess moisture and then enter the unit’s mass sensor. As the 

airflow passes through the mass sensor, an exchangeable filter cartridge collects the respirable 

particles. The mass sensor can be removed from the PDM by a mine’s dust technician (Figure 3) 

to change the particle collection filter and clean the unit after the end of each work shift. 

5
Filter

 Figure 3.—Technician changing filter 

on the PDM mass sensor using a customsupplied filter tool. 

Flow Measurement and Control 

Downstream of the mass sensor, the filtered airstream flows through an orifice used in 

conjunction with a differential pressure measurement to determine the volumetric flow rate. 

In-line relative humidity (RH) and temperature sensors are located ahead of a computercontrolled sample pump that generates the vacuum needed to sample the mine atmosphere. 

Other sensors measure the ambient temperature in the vicinity of the cyclone, as well as the 

atmospheric pressure in the mine. The PDM uses these inputs, together with the sample 

airstream temperature sensed close to the flow-measurement orifice, to determine the flow rate 

passing through the HD cyclone. A feedback loop in the PDM uses this information to 

dynamically control the speed of the pump so that the constant 2.2-L/min volumetric flow rate, 

required for proper dust size separation, is maintained at the cyclone, under the mine’s ambient 

temperature and pressure conditions. 

Battery Configuration 

The two identical battery packs inside the PDM provide 12 hr of power to the miner’s cap lamp 

and the particle sampling and analysis system. The batteries can be recharged from a complete 

discharge in about 6 hr to provide maximum use of the monitor. The batteries make use of the 

latest lithium-ion technology used in portable computers to provide high-power density and 

superior charging and life cycle characteristics. The energy storage density enabled by lithiumion battery technology allows for the packaging of a dust sampling and analysis system together 

with the batteries required for the cap lamp in a size and weight approximating those of the 

current battery pack. The PDM as tested weighed 3.0 kg (6.6 lb). 

6
 
Data Treatment 

A microprocessor-based controller collects real-time inputs from sensors and the microbalance to 

provide a minute-by-minute record of the dust loadings and mine environment. The PDM 

continuously displays personal dust exposure information to the miner in numeric and graphic 

formats. Environmental data such as ambient temperature, pressure, and motion of the 

instrument are measured. Dust and environmental data are stored in the PDM memory for about 

20 full-shift sample runs. These data may be selected for downloading and analysis. 

An illuminated data display on the top of the PDM continuously shows the previous 30-min dust 

concentration, cumulative mass concentration to that point in the shift, and an estimated EOS 

projected concentration exposure. Through the display, miners can gauge their current dust 

exposure, as well as the effectiveness of actions taken to reduce their dust exposure. 

The exposure data described above are always displayed to miners, but are protected from 

tampering by being accessible only to an authorized person. In addition, the PDM allows miners 

and management to initiate short-term mass concentration measurements for specific monitoring 

objectives without affecting the shift-based statistics. This can be helpful to gauge the 

effectiveness of various dust or ventilation engineering control techniques. These intrashift 

measurements may be made as often as desired, and data obtained during these trials may be 

selected for downloading together with the tamper-resistant shift-based information. 

TEOM Mass Measurement Technique 

At the heart of the TEOM mass sensor is a hollow tube, called the tapered element (TE), which is 

clamped at its base and free to oscillate at the opposite end. The exchangeable filter cartridge 

mounted on its free end collects the respirable particles contained in the airstream that passes 

from the entrance of the mass sensor through the TE. Electronic components positioned around 

the TE cause the tube to oscillate at its natural (or resonant) frequency and at a constant 

amplitude. As additional mass collects on the sample filter, the natural oscillation frequency 

decreases as a direct result. This approach uses first principles of physics to determine the mass 

change of the collection substrate (filter) and is not subject to uncertainties related to particle 

size, color, shape, or composition. 

The PDM determines the mass concentration of respirable dust in the mine environment by 

dividing the mass (as determined by the frequency change) collected on its filter over the air 

volume sampled during the same period. The system updates its mass concentration readings, 

shown in milligrams per cubic meter, every few seconds. The manufacturer uses mass standards 

traceable to the National Institute of Standards and Technology to calibrate the mass sensor 

constant K0, which determines the relationship between mass change at the end of the TE and 

frequency change. 

7
 
Filter mass is calculated every 5 sec according to 

⎛ 1 1 ⎞ MT 0 = K 0 × ⎜ − ⎟ ⎜ 2 2 ⎟ (1) ⎝ f c f i ⎠

where MT0 = mass; 

K0 = the constant of the tapered element (TE); 

fc = current frequency; 

and fi = initial frequency (i.e., at start of shift). 

Mass rate and concentrations are derived from the mass, time, and flow rates of the instrument. 

Details of these calculations may be found in the operations manual [Rupprecht and Patashnick 

Co. 2004]. 

Momentum Compensation: The Key to Miniaturization 

In the past, TEOM-based monitors were much too large and delicate to be used for personal 

exposure monitoring [Williams and Vinson 1986]. The potential for application of the TEOM 

technology to mining came through the miniaturization of the TEOM mass detector, which was 

made possible through the development of a patented concept involving momentum 

compensation. A momentum compensator, built into the PDM mass sensor, oscillates an 

additional mass at the same frequency, but in opposing phase to the TE. The TE effectively 

behaves as if it were mounted on a massive base without the use of a large mass. By analogy, 

a musical tuning fork requires two forks rather than a single fork to freely oscillate. The purpose 

of the second fork is to provide momentum compensation to the first fork by oscillating in an 

equal but opposite motion as the primary fork. This momentum compensation allows a user to 

hold a tuning fork base without extinguishing its motion, and it will ring freely for a long period. 

A tuning fork would not ring freely with a single fork unless it was held in a base of significant 

mass and clamped such that there is very little energy loss to the system. By applying this 

principle, energy loss from the TE oscillator to its surroundings approaches zero with the 

appropriate proprietary design of the momentum compensator. The size and weight of the TEOM 

detector are dramatically reduced without compromising performance. In addition, the smaller 

sensor reduced the thermal heating requirements, enabling greatly reduced power consumption. 

METHODS 

Laboratory Methods 

Performance of the precommercial series 3600 PDM was evaluated in the laboratory to validate 

instrument accuracy as received from the manufacturer and after use in mines. Using published 

criteria for comparing analytical techniques [Kennedy et al. 1995], NIOSH showed that for the 

prototype PDM, “there is a 95% confidence that the individual PDM measurements were within 

±25% of the reference measurements” and that the upper 95% confidence limit was met 

[Volkwein et al. 2004]. The precommercial 3600 PDM uses the same mass measurement 

methods and algorithms as the prototype, and a detailed repeat of the entire accuracy evaluation 

was not warranted. However, to confirm this assumption, a limited version of the previous 

accuracy test was conducted with all of the new instruments. 

8
 
Dust Exposure Chamber 

A laboratory Marple chamber provided a uniform test environment for comparing dustmeasuring instruments while maintaining good control of test variables [Marple and Rubow 

1983]. The chamber was operated to produce dust concentrations nominally ranging from 0.2 to 

4 mg/m3

. While this is the concentration range recommended in NIOSH’s Guidelines for Air 

Sampling and Analytical Method Development and Evaluation [Kennedy et al. 1995], it was 

viewed as a guideline since it pertains to analytes that have very good reference standards. In 

this case, the reference was a gravimetric sampler. The relative standard deviation (RSD) of 

these samplers has been demonstrated [Kogut et al. 1997] to significantly increase at mass 

concentrations of less than 0.5 mg/m3. When reference mass loadings were less than 0.5 mg/m3, 

the number of reference samples was increased to improve the accuracy of the reference mass 

measurement. Coal dust used in the chamber was from the Pittsburgh Seam and was ground to 

size by passing the coal through an Alpine AFG Model 100 jet mill (Hosokawa Micron Powder 

Systems, Summit, NJ). A fluidized bed dust generator with charge neutralizer (TSI, Inc., 

St. Paul, MN) was used to introduce the dust into the chamber. 

Chamber temperature was regulated to between 20 and 25 °C and an RH between 40% and 60%. 

Instruments were mounted on a turntable in the chamber that was rotated at a rate of one to two 

revolutions per minute. This eliminated the need for a randomized block design and ensured that 

each sampling device was exposed equally to all radial portions of the chamber. Chamber dust 

concentrations were monitored with a commercially available Model 1400a TEOM (TEC, 

Albany, NY). This was used to help select the correct time intervals to achieve desired mass 

loadings for the testing. 

Samplers 

PDM mass measurement accuracy and precision were compared to the average of multiple 

gravimetric samples. A total of 25 PDMs were used as delivered by TEC. Samplers used 

for gravimetric analysis were BGI–4CP cyclones with integral filter holders (BGI, Inc., 

Waltham, MA) connected to MSA Escort ELF sampling pumps (MSA Co., Inc., Pittsburgh, PA). 

The BGI–4CP cyclone was an HD design, identical to that used in the PDM. The PDMs and 

the BGI–4CP cyclones were operated at 2.2 L/min. To further minimize test variables, the BGI– 

4CP samplers were modified to use an inlet and tube configuration identical to that in the PDMs. 

PDM 

The PDM used Teflon-coated nominal 15-mm-diam filter media TX40H120WW (Pallflex 

Products Corp., Putnam, CT), manufactured into a special plastic holder that mounted on the end 

of the hollow TE. This is the same filter medium used in the TEC Model 1400a ambient air 

monitor. The PDM sampler flow rate was checked and recalibrated if flow variance was greater 

than ±1% (0.022 L/min). Data on the flow rate and calibration of each instrument were 

recorded. The analysis of flow rate stability was based upon 10 PDM units for which complete 

flow calibration histories were known. 

9
 
PDM samplers were cleaned after each day of use. Cleaning consisted of removing the cyclone 

grit pot, the TE sensor module, and the filter on the TE. Canned compressed air was then blown 

from the cap lamp-located inlet tube toward the cyclone, up the cyclone from the grit pot, and 

from the TE connection back toward the cyclone. The TE module and cyclone grit pot were then 

cleaned with the compressed air. A new filter was installed on the TE and the module and 

cyclone grit pot reattached to the PDM. 

Gravimetric Reference 

The filters used in the BGI–4CP cyclone were 37-mm-diam, 5-μm pore size, polyvinyl chloride 

(PVC) membranes. Flow-controlled MSA ELF Escort pumps were calibrated on-site at the 

beginning of each group test using a Gilibrator (Sensidyne, Inc., Clearwater, FL) primary 

standard flow meter to 2.2 ± 0.022 L/min for the BGI–4CP samplers. A pressure restriction 

equivalent to the respective samplers was used during pump calibration. 

Impactors 

Size distributions of the dust in the chamber were measured using a Marple personal cascade 

impactor (Model 290, TEC, Franklin, MA) operated at a flow rate of 2.0 ± 0.020 L/min using 

ELF Escort pumps. The device was operated according to the manufacturer’s instructions, 

including correction factors to account for inlet efficiency and wall loss [Rubow et al. 1987]. 

The impactor has eight collection stages with cut points from 0.52 to 21.3 μm and a final filter 

(PVC 37-mm-diam, 5-μm pore size). At each collection stage, dust particles impact on a 

34-mm-diam Mylar® substrate at six impaction zones. Before using the substrates, the 

impaction zones were coated with grease to hold the collected particles on the substrates. This 

was done by covering the 34-mm-diam Mylar substrate with a metal template that has six slots 

that expose the impaction zones. These slots were then sprayed with a 1- to 10-μm-thick layer of 

impaction grease (Dow Corning 316 Silicone Release Spray, Dow Corning Corp., Midland, MI). 

After spraying, the substrates were kept at constant temperature and humidity for 3 days to allow 

the volatile components of the silicone spray to evaporate and to outgas. The substrates and the 

PVC final filters were then preweighed and loaded into the eight stage impactors. Impactors 

were used in triplicate to measure the size distribution of the coal dust. Three substrates and 

three final filters were used as blank controls. 

The size distribution mass median aerodynamic diameter (MMAD) and geometric standard 

deviation (GSD) were determined from a straight line regression of impactor stage data plotted 

as the inverse cumulative distribution function of the normal distribution or probit of cumulative 

mass percentages versus the logarithm of stage cut point. The use of straight line regression to 

find the best-fitting line for this type of plot is recommended only if the regression is truly linear 

because it overemphasizes the tails of the distribution. Cumulative lognormal plots often show 

curvature toward the tails, resulting in regression error of the distribution parameters [Hinds 

1982]. To account for a potential error caused by overemphasis of the tails of the distribution, 

data for size distribution analysis were only used if the R2

 values for the regression were greater 

than 0.95. 

10
 
Analytical Gravimetric Precision 

Gravimetric analysis was performed on a Cahn microbalance (model C–31, TEC, Boston, MA) 

for the impactor samples and a Mettler-Toledo microbalance (model UMT2, Mettler-Toledo, 

Inc., Columbus, OH) for the BGI–4CP and CMDPSU samples. Weighing was done in the 

NIOSH Pittsburgh Research Laboratory’s (PRL) weighing laboratory at 73 ± 0.7 °F and 53 ± 

2% RH. All samples were pre- and postweighed using control filters. Average blank control 

filter weights were used to correct the filter mass results for each test employing impactors, BGI– 

4CP cyclones, and the CMDPSU. However, small cyclic fluctuations in these conditions over 

the course of a few minutes cannot be totally accounted for by the control filters for two reasons. 

First, the control filters cannot physically be weighed at the same time as the sample filters. 

Secondly, the pre- and postweighings are not performed at the same time in relation to the cyclic 

variation of the room conditions. Therefore, several estimates for the weighing precision will be 

provided. 

Experimental Design 

Because of the limited weight and volume capacity of the Marple chamber, the 25 PDMs were 

usually divided into two groups with 12 and 13 instruments per group. Three replicate test runs 

were conducted with each group. Each individual test run used 15 BGI–4CP gravimetric 

samplers. The inlets of all samplers were uniformly arrayed around a central point in the Marple 

chamber (Figure 4). 

11
 

Figure 4.—Laboratory test chamber and arrangement of instruments. 
 

The 15 gravimetric samplers were arbitrarily divided into four test-time interval groups. A testtime interval was defined as the time required to achieve a predetermined mass for a group of 

instruments. The first time interval used six samplers to account for the increased variability of 

the reference measurement when mass loadings were less than 0.5 mg/m3

; the second, third, and 

fourth time intervals used three samplers. 

The mass collected by the samplers in each time group was used to determine the average 

reference gravimetric dust mass during a specific test-time interval. In addition, there were three 

blank control filters for each test. Control filters were handled in an identical fashion to the test 

filters, except that the cassette end caps were not removed. Final test filter weights were 

corrected using the average control filter mass change. 

Test-time intervals were selected to achieve filter mass target loadings over the range of about 

0.2–4 mg. For a typical test run, the internal computer for each PDM was programmed to 

automatically start and all gravimetric samplers were manually started at the same time. Because 

of the large number of gravimetric samplers started manually, they were started sequentially by 

group and stopped in the same sequence to minimize any time differences between samplers 

caused by starting and stopping. As mass loaded onto the samplers with time, groups of 

gravimetric sampling pumps were turned off at predetermined mass loadings, as indicated by the 

Model 1400a TEOM using an HD cyclone at a flow rate of 2.2 L/min. The mass loading 

therefore determined the test-time interval. This procedure resulted in four test-time intervals 

with averaged mass loadings from corresponding groups of BGI–4CP samplers. For each testtime interval, the PDM mass measurements, preserved in data files, were used to determine the 

mass measured by the individual PDM for that test-time interval. 

The three test runs were essentially replicates except that the mass loadings varied as follows: 

• Run 1.—8-hr duration, test-time interval Nos. 1–4. The chamber was brought to a 

concentration of about 2 mg/m3

. Gravimetric filters were turned off at equivalent mass target 

loadings of 0.4, 0.9, 1.4, and 2 mg. Impactor size distribution samples were taken with three 

impactors to confirm that the size distribution of this study was comparable to previous sizes 

associated with this coal type. 

• Run 2.—8-hr duration, test-time interval Nos. 5–8. The chamber was brought to a 

concentration of about 4 mg/m3

. Gravimetric filters were turned off at equivalent mass target 

loadings of 1, 2, 3, and 4 mg. 

• Run 3.—8-hr duration, test-time interval Nos. 9–12. The chamber was brought to a 

concentration of about 2 mg/m3

. Triplicate sets of filters were turned off at equivalent mass 

target loadings of 0.2, 0.7, 1.7, and 2.0 mg. 

PDM Battery Test 

Previous work had demonstrated that the lithium-ion batteries used in the PDM could enable a 

12-hr sample to be taken, but did not address what happens to PDM performance as batteries 

weaken prior to failure. A test was conducted with six PDMs to monitor mass rate of 

accumulation and flow rate as the instruments’ batteries ran out of power. This laboratory 

12
 
 

 

testing established a dust concentration of 2 mg/m3 in the Marple chamber that was continuously 

monitored using a Model 1400a TEOM and PDMs run to battery failure. 

PDM Mass Constant Verification 

During this evaluation, the mass constant of the PDM was verified. To determine mass, each 

individual TE used in a PDM has an empirically derived mass constant. 

Definition of Constant 

The constant K0 (K zero) is determined by recording the TE’s frequency change due to a known 

mass applied to the TE’s filter and inputting data into the following equation: 

m K0 = 2 2 (2) ( (1/ f )− (1/ f )) f i 

where K0 = the constant of the TE; 

m = the mass in grams added to the TE filter; 

fi = the baseline frequency in hertz of the TE before the mass is added; 

and ff = the frequency in hertz of the TE after the mass is added. 

The K0 for each TE was determined by averaging five K0 measurements. The K0 was calculated 

each time the mass on the TE was changed. The resulting average was then compared with the 

K0 that had been programmed by TEC into each PDM. 

Procedure to Determine Mass Constant 

All of the PDMs were cleaned and had new filters inserted on their TEs. Their inlets were 

connected to a high-efficiency particulate air (HEPA) filter to eliminate the possibility of dust 

contamination. Throughout the tests, each PDM was connected to their battery charger/computer 

connection, which enabled real-time graphing of the TE frequency. The PDMs were run for a 

minimum of 1 hr for warmup before any K0 measurements were made. 

The known masses added to the TE filter were small, preweighed aluminum tabs with adhesive 

on one side of the tab to couple the tab to the filter surface. The tabs were preweighed just 

before the tests in the controlled atmosphere of the PRL weighing laboratory. 

After warmup, the PDMs were programmed with the WinPDM 5.12A expert software program 

to activate the mass raw frequency template and to display and log data every second. The 

software program graphed the raw frequency curve in real time. By observing this curve, we 

could determine when the raw frequency had stabilized. The stabilized baseline frequency (fi) 

was recorded. The TE module was removed from the PDM, and a preweighed aluminum tab 

was attached near the center of the TE filter. The TE module was then reinserted into the PDM 

and the raw frequency curve observed. Once the raw frequency had stabilized, the new 

frequency (ff) was recorded along with the mass of the aluminum tab. This process was repeated 

five times. Each additional piece of aluminum mass was uniformly distributed across and 

13
 
adhered to the filter. Mass at each frequency was the summation of the individually added 

pieces. The K0 for each mass was then calculated according to equation 2 and the average K0 of 

the five readings calculated. This averaged K0 was then compared with the K0 that had been 

programmed into the PDM. 

Analysis 

The accuracy and precision were calculated from the data pairs of individual PDM mass 

measurements to the average gravimetric reference standard. Accuracy, bias, and precision were 

calculated by the method of Kennedy et al. [1995], who defined accuracy to be the ability of a 

method to determine the true concentration, bias to be uncorrectable relative discrepancy 

between the mean of the distribution and the true concentration, and precision to be the relative 

variability of measurements of replicate samples about the mean of the population of 

measurements. For these tests, the mass ratio for each datum pair was calculated by dividing the 

individual PDM mass by the average value for the triplicate gravimetric reference mass 

measurements of the corresponding time interval. The individual mass ratios were then averaged 

over each group of data. The RSD was calculated for both PDM and gravimetric reference 

standards. To reduce the impact of error in the gravimetric reference measurement, the 

experimental pooled estimate of the RSD of the gravimetric samplers was subtracted from the 

RSD of the ratios such that the corrected RSD was 

14
 

RSD = 

2

 2 x RSDx - RSDTi 

 (3) 

t 

RSD where x = relative standard deviation of mass ratio t 

and the experimental pooled RSD of the gravimetric samplers was 

 

RSD gravimetric 

RSD (4) T i = 

2

n 

2 ∑

Bias was then calculated based on the mean concentration minus one. Accuracy was calculated 

based on the method provided by Kennedy et al. [1995]. Confidence limits were calculated 

based on the method used by Bartley [2001] using the noncentral Student’s t-distribution. 

The precision of the PDM was analyzed for each test by examining the RSD of the PDM and 

reference samplers over mass loadings ranging from 0.2 to 4.3 mg. To determine the overall 

precision of the PDM from the premine laboratory data, an RSD was computed using a one-way 
analysis of variance (ANOVA). The intratest RSD was estimated by the square root of the mean 

square error (RMSE). The dependent variable for this analysis was the dust concentration 

measured in milligrams per cubic meter, and the independent (or grouping) variable was the 

laboratory test. There were six tests with 12–13 PDMs per test. For each test, dust concentration 

measurements were collected at four time intervals. For each PDM, the dust measurements were 

averaged across the time intervals within each individual test. In order to be consistent with the 

methodology used to calculate the PDM field precision, the concentration measurements were 

log-transformed (log base e) before the analysis was conducted. 

Detailed In-mine Test Methods 

In this portion of the study, PDMs were used by miners to estimate the long-term mechanical, 

functional, and ergonomic features of the samplers. The in-mine precision of the PDM and 

reference samplers was determined. 

Criteria for Mine Selection 

This testing required a high level of cooperation from the host mine to permit training, allocate 

working space, and commit labor to maintain the PDMs in the absence of NIOSH personnel. 

The level of cooperation required prevented selection of mines at random for this portion of the 

testing. Mines were, however, selected to include a variety of coal types, machine types, 

geographic locations, seam heights, and workforce sizes. Representative geographic distribution 

of mines was achieved by selecting one mine from each of the 10 MSHA bituminous coal 

mining districts. Table 1 shows the characteristics of each mine. Within this sample, selections 

were made by type of machine and on-section locations to obtain dust samples that were 

representative of where miners work. 

Table 1.—Detailed mine characteristics and location of Lippmann sample 

MSHA 

district 

Mine

height, 

in 

Mining

method Distinguishing features Location of sample 

2 ............. 65 CM Exhaust vent tube, integral miner bolter ............. On miner left rear side. 

3 ............. 70 CM Exhaust vent tube, integral miner bolter........... On miner near left bolter. 

4 ............. 65 LW PDM powered remote ........................................ Shield 30. 

5 ............. 48 CM Scrubber, bridge face haulage ........................... Immediate miner return. 

6 ............. 56 CM Small mine.......................................................... Bolter. 

7 ............. 50 CM Pillar section – retreat ventilation to gob............. Behind miner toward gob side. 

8 ............. 46 CM Super section single split vent, low coal ............. Immediate miner return. 

9 ............. 120+ LW High seam .......................................................... Shield 20. 

10 ........... 46 CM Low coal, super section...................................... Immediate miner return. 

11 ........... 72 CM Diesel face haulage............................................ Twin boom bolter. 

CM Continuous mining. LW Longwall. 

Detailed Mine Procedures 

At each detailed mine test site, NIOSH spent 3 days on-site to demonstrate and teach mine 

personnel how to use and maintain the PDM. Sampling of an entire face crew was conducted 

over the miners’ entire work shift, which included travel to and from the working section. In 

15
 
 

addition, the precision of triplicate samplers was determined. The PDMs were then left at 6 of 

the 10 mines for use by the mine without NIOSH present. At the end of the 10th detailed mine 

study in late spring of 2005, four mining companies conducted extended testing of the PDM at 

their mines to further evaluate the stand-alone performance of the instrument. 

At each mine, NIOSH presented a 45-min training session at the start of the shift. The training 

contained a short video to ensure that information was presented in a uniform manner. A pocketsized memory jogger card was given to each miner wearing a PDM to remind him or her about 

the points discussed in the video. The mine section where miners were to wear the PDM was 

selected by management and hourly employee representatives. In addition to the section crew, 

management and labor representatives and safety personnel attended the training. NIOSH 

provided additional training to the mine employees who would maintain the PDMs at the mine. 

Data collected at each mine included the full-shift dust exposure of each miner, the 

corresponding MSHA-coded occupation, and a notation of any problems in collecting the data. 

Mine personnel programmed the PDMs to automatically start sampling at the beginning of the 

shift and to sample for the entire shift length. Between 7 and 14 PDMs were used depending on 

the size of the section crew. Each day, miners picked up their assigned PDM as they would have 

normally picked up their cap lamps and returned the PDM to the charger at the end of the shift. 

A mine employee would then download the data, clean the inlet tube and cyclone, change the 

filter, and program the samplers for the next shift of sampling. Data from the samplers were 

considered valid when the PDM ran for the entire shift with no mechanical or electronic faults, 

or human errors. This mechanically correct sample could later be considered void in the event 

that the data file showed a flow fault or other sampling abnormality. The number of 

mechanically correct samples divided by the total number of samples attempted during a shift 

determined the overall valid or sampling success rate for this testing. Subsequent analysis of the 

data file may determine that a sample should be voided for cause, but this would not affect the 

overall valid sampling rate. Flow rates for these PDM samplers were considered acceptable at 

±5% of 2.2 L/min. In the event that the PDM flow sensor detected a flow rate change that was 

greater than ±0.2 L/min of the calibrated flow for a period of 60 sec, the PDM would place an 

error message on the display and in the datum file for later evaluation of the severity of the fault. 

For the first 3 days of sampling, NIOSH personnel collected area samples, were present on-site 

to help with the PDM sampling, and accompanied the miners underground to answer questions. 

At the first six mines, NIOSH left all of the PDMs for the section crew at the mine site under the 

supervision of mine personnel. The same section of miners continued to use the PDMs for the 

next week. If a miner was absent, the miner’s replacement would wear the PDM. Similarly, 

if the entire crew changed from day to evening shift, the PDMs stayed with that crew to maintain 

consistency. If extra instruments were available, other miners working outby8

8

Away from the area of active mining. 

16
 

 would 

occasionally wear a PDM. The following week, NIOSH returned to the mine and accompanied 

the section crew to work. NIOSH observed and talked to miners about their experience with the 

PDM. We then collected the instruments and data records. This resulted in 8–11 shifts of data 

from each PDM from every member of the mining section. The variable number of days 

resulted from some mines continuing testing through the weekend or scheduled shift changes. 
Area Sampling 

Area sampling was conducted for 3 days at each mine to determine the precision of the PDM, 

DO cyclone, and impactor size distribution measurements. A stationary Lippmann-type 

sampling apparatus [Blachman and Lippmann 1974; Volkwein and Thimons 2001] was used to 

collect triplicate measurements from the PDM, Marple personal impactors, and CMDPSUs at 

flow rates of 2.0 L/min and 1.7 L/min. The Lippmann device minimized spatial variability 

associated with mine sampling. Weighing and calibration procedures for this testing were 

identical to the laboratory testing. The 3 days of sampling conducted in 10 mines resulted in a 

total of 30 triplicate measurements from which the precision of instruments was calculated. 

Maintenance and Use Log 

Over the course of the research, all usage of the project’s 25 PDMs was recorded. A chronological 

record was kept for each PDM unit summarizing the number of hours it actively ran from its 

delivery date to the end of the project. This included all types of laboratory and field operations, 

regardless of the nature of the usage, test, or monitoring being performed. Therefore, for the 

purpose of summarizing overall PDM use, only total hours logged were considered, and the 

environment or nature of differing instrument deployments was not a distinguishing factor. 

Each PDM also had its individual repair history recorded, which included some details of 

problems experienced and repairs performed to resolve the problems. For these repair records, 

distinctions were made between types of manufacturer repair. Repairs were categorized as either 

remedial or critical. Remedial repairs reflected current or pending hardware or software 

modifications to instrument design that were minor in nature and unlikely to be ongoing issues 

once fully instituted. Examples of remedial repairs include updating firmware to correct 

performance problems, correcting manufacturing defects, and replacing failed faceplate keypads 

or display screens. Critical repairs were defined as repairs necessary for full functional operation 

of the instrument to collect valid data. Critical repair frequency was regarded as somewhat more 

reflective of ultimate instrument reliability after design refinements. 

Further maintenance log entries were also made to record success or failure of each PDM run. 

If a PDM completed a run with valid data, the run was evaluated as successful. If a run was not 

completed or data files were electronically corrupted, the run was considered a failure. While 

the nature of run failures was recorded, types of failures were not subcategorized. Researchers 

intervened and corrected unsuccessful PDM performance as soon as problems were recognized. 

In many instances, minor adjustments were adequate to resolve instrument problems. Less 

frequently, manufacturer service was required and recorded. 

Field Precision Analysis 

To determine the precision of the PDM, the DO cyclone at 2.0 L/min, and the DO cyclone at 

1.7 L/min, the RSD was computed using a one-way ANOVA. To determine the within-day 

variability average among the triplicate samplers, a technique using the standard deviation 

calculated from the ANOVA was used to compute the RSD. Because the distributions of the 

dust concentrations for each sampler were positively skewed, the data values were log17
 
transformed (log base e) before the analysis. The dependent variable for this analysis was the 

dust concentration measured in milligrams per cubic meter, and the independent (or grouping) 

variable was the date of the in-mine sampling test. There were 30 unique dates with triplicate 

measurements collected on each date for each instrument type. 

RESULTS 

Laboratory Accuracy Verification 

The ability of the PDM to determine the true concentration of aerosol in the environment is 

described as the instrument’s accuracy. Evaluation of the data from the prototype PDM to 

determine whether it met the NIOSH accuracy criterion was reported by Volkwein et al. [2004]. 

The limited lab premine testing reported here was intended to verify that the precommercial 

3600 PDM maintained performance similar to that of the prototype PDM. 

Premine Testing 

Premine accuracy verification test results in Table 2 present the average mass of dust from the 

BGI–4CP samplers for each test-time interval, the corresponding individual PDM mass 

measurements by serial number, and the RSD of both samplers. The overall average RSD for the 

gravimetric reference sampling for these laboratory samples is 0.041 for the first group of tests 

and 0.039 for the second group. The RSD for the PDM units for each test-time interval is 

indicated; the average for these measurements was 0.057 for the first group of tests and 0.043 for 

the second group. The RSD of the combined data calculated for the PDM was 0.051 (95% CL = 

0.048, 0.057). This value will be subsequently used in the discussion of the calculation of field 

precision. 

18
 
Table 2.—Premine laboratory data of reference mass measurements and PDM mass measurements 

Time 

interGravimetric 

avg. RSD 110 112 113 115 119 

PDM mass by serial number 

126 127 128 130 131 132 133 135 RSD 

val mass, 

mg mg mg mg mg mg mg mg mg mg mg mg mg mg 

1 

2 

3 

4 

5 

6 

7 

8 

0.426 

0.968 

1.506 

2.184 

1.132 

2.160 

3.244 

4.308 

0.048 

0.047 

0.033 

0.023 

0.033 

0.049 

0.054 

0.036 

0.377 

0.901 

1.384 

1.931 

1.050 

2.104 

3.075 

3.980 

0.406 

0.956 

1.481 

2.054 

1.066 

2.163 

3.161 

4.090 

0.384 

0.903 

1.397 

1.942 

0.994 

1.991 

2.910 

3.757 

(

1

) 

(

1

) 

(

1

) 

(

1

) 

0.955 

1.929 

2.833 

3.675 

0.409 

0.958 

1.483 

2.053 

1.052 

2.098 

3.068 

3.970 

0.388 

0.903 

1.397 

1.933 

1.047 

2.115 

3.110 

4.027 

0.359 

0.939 

1.462 

2.036 

1.013 

2.032 

2.976 

3.843 

0.431 

0.992 

1.515 

2.108 

1.124 

2.254 

3.298 

4.271 

0.413 

0.952 

1.453 

2.020 

1.033 

2.097 

3.076 

3.989 

0.393 

0.897 

1.363 

1.887 

1.009 

2.000 

2.923 

3.795 

0.414 

0.967 

1.481 

2.064 

(

1

) 

(

1

) 

(

1

) 

(

1

) 

0.357 

0.843 

1.289 

1.792 

0.935 

1.839 

2.658 

3.425 

0.381 

0.881 

1.354 

1.884 

1.061 

2.115 

3.087 

3.975 

0.058 

0.046 

0.048 

0.048 

0.050 

0.054 

0.055 

0.056 

9 0.193 0.082 0.196 0.202 0.201 0.202 0.212 0.196 0.204 0.205 0.222 0.197 0.203 0.165 0.214 0.066 

10 0.747 0.021 0.732 0.732 0.733 0.727 0.774 0.732 0.741 0.757 0.800 0.701 0.759 0.596 0.797 0.069 

11 1.796 0.033 1.688 1.700 1.702 1.689 1.792 1.697 1.720 1.776 1.837 1.637 1.788 1.396 1.833 0.066 

12 

Ave

2.144 

rage 

0.033 1.967 1.984 1.975 1.959 2.076 1.968 1.993 2.072 2.139 1.909 2.074 1.633 2.124 0.064 

gravimetric 

RSD 

 

0.041 Average PDM RSD 0.057 

 

Time 

interGravimetric 

avg. RSD 102 105 108 109 111 

PDM mass by serial number 

114 116 120 122 123 124 125 115 132 RSD 

val 

1 

 mass, 

mg 

0.424 0.069 

mg 

0.410 

mg 

0.377 

mg 

0.376 

mg 

0.432 

mg 

0.451 

mg mg mg 

0.395 0.427 0.391 

mg 

0.430 

mg 

0.426 

mg 

0.372 

mg 

0.411 

mg 

0.400 

mg 

0.061 

2 1.003 0.025 0.914 0.854 0.860 0.967 0.989 0.887 0.971 0.889 0.960 0.960 0.840 0.925 0.901 0.054 

3 1.572 0.034 1.454 1.354 1.376 1.508 1.571 1.406 1.544 1.415 1.521 1.515 1.331 1.481 1.433 0.052 

4 2.115 0.034 1.990 1.865 1.917 2.055 2.149 1.927 2.125 1.949 2.076 2.082 1.836 2.037 1.973 0.049 

5 1.111 0.044 1.055 1.008 0.993 1.009 1.089 1.011 1.095 1.059 1.028 1.108 1.048 1.076 1.066 0.035 

6 2.169 0.002 2.024 1.928 1.918 1.930 2.097 1.957 2.108 2.035 1.974 2.131 2.016 2.070 2.055 0.036 

7 3.224 0.042 2.999 2.890 2.874 2.864 3.130 2.914 3.124 3.028 2.961 3.159 2.978 3.067 3.058 0.034 

8 4.213 0.030 3.846 3.709 3.689 3.683 4.002 3.744 4.012 3.891 3.814 4.046 3.809 3.927 3.916 0.032 

9 0.185 0.076 0.203 0.202 0.192 0.199 0.204 0.191 0.205 0.194 0.198 0.203 0.181 0.218 0.045 

10 0.724 0.025 0.730 0.721 0.692 0.717 0.736 0.703 0.758 0.710 0.724 0.750 0.676 0.768 0.037 

11 1.814 0.040 1.742 1.722 1.646 1.702 1.777 1.673 1.798 1.685 1.722 1.772 1.613 1.839 0.038 

12 

Ave

2.035 

rage 

0.051 2.005 1.985 1.893 1.969 2.041 1.936 2.075 1.952 1.987 2.043 1.867 2.117 0.037 

gravimetric 

RSD 0.039 1

Test run in group 2. 

 Average PDM RSD 0.043 

The average triplicate size distribution measurement of the coal dust in the chamber had an 

MMAD of 3.91 μm (RSD = 0.007) and a GSD of 2.58. This was comparable to the 

intermediate-sized Pittsburgh coal dust used in the accuracy determination of the prototype 

instrument [Volkwein et al. 2004]. 

Postmine Testing 

Postmine testing accuracy verification data in Table 3 show the average mass of dust from the 

triplicate BGI–4CP samplers for each test-time interval, the corresponding individual PDM mass 

measurements, and the RSD of both samplers. The overall average gravimetric reference 

sampling RSD for this work was 0.039 for the first group of tests and 0.049 for the second group. 

The PDM units’ RSD for each test-time interval is indicated. The average RSD for these 

measurements was 0.056 for the first group of tests and 0.051 for the second group. The average 

size distribution of the coal dust for postmine testing had an MMAD of 4.01 μm (RSD = 0.079) 

and a GSD of 2.53. 

19 
Table 3.—Postmine laboratory data of reference mass measurements and PDM mass measurements 

Gravi­ PDM mass by serial number Time metric 102 108 112 113 114 115 119 120 123 124 125 127 128 inter- avg. RSD RSD 

val mass, mg mg mg mg mg mg mg mg mg mg mg mg mg 

mg 

1 0.425 0.026 (

1

) 0.373 0.445 0.397 0.359 0.386 (

1

) 0.410 0.404 0.405 0.429 0.418 0.388 0.058 

2 0.960 0.030 (

1

) 0.817 0.953 0.861 0.788 0.832 (

1

) 0.895 0.880 0.885 0.932 0.892 0.850 0.053 

3 1.475 0.065 (

1

) 1.281 1.463 1.344 1.220 1.278 (

1

) 1.368 1.369 1.365 1.438 1.373 1.328 0.048 

4 1.950 0.029 (

1

) 1.717 1.955 1.794 1.629 1.720 (

1

) 1.827 1.833 1.833 1.923 1.822 1.777 0.046 

5 1.012 0.049 0.885 0.875 0.995 0.890 0.824 0.865 0.931 0.982 0.946 0.931 1.010 0.947 0.924 0.064 

6 1.931 0.038 1.759 1.741 1.972 1.764 1.638 1.740 1.859 1.947 1.870 1.843 1.995 1.891 1.833 0.061 

7 2.899 0.033 2.639 2.608 2.958 2.656 2.460 2.627 2.789 2.919 2.809 2.763 2.981 2.827 2.751 0.060 

8 3.906 0.038 3.576 3.512 3.997 3.601 3.329 3.566 3.757 3.938 3.801 3.741 4.011 3.821 3.730 0.058 

9 0.209 0.048 0.185 0.173 0.202 0.189 0.162 0.179 0.193 0.197 0.191 0.190 0.184 0.193 0.189 0.061 

10 0.709 0.047 0.669 0.621 0.692 0.652 0.585 0.647 0.673 0.701 0.707 0.689 0.661 0.675 0.658 0.054 

11 1.738 0.042 1.601 1.506 1.672 1.568 1.420 1.560 1.620 1.667 1.714 1.647 1.580 1.628 1.591 0.052 

12 2.114 0.028 1.874 1.772 1.963 1.848 1.664 1.836 1.907 1.964 2.000 1.940 1.856 1.913 1.865 0.051 

Average 

gravimetric 

RSD 0.039 Average PDM RSD 0.056 

 

 

Gravi­ PDM mass by serial number Time metric 105 109 110 111 116 122 126 130 131 132 133 135 102 119 inter- avg. RSD RSD 

val mass, mg mg mg mg mg mg mg mg mg mg mg mg mg mg 

mg 

1 0.395 0.044 0.361 0.355 0.353 0.323 0.378 0.385 0.371 0.367 0.329 0.342 0.336 0.353 0.363 0.378 0.053 

2 0.962 0.062 0.831 0.800 0.786 0.728 0.843 0.869 0.823 0.817 0.758 0.771 0.752 0.786 0.830 0.864 0.053 

3 1.425 0.007 1.283 1.228 1.205 1.128 1.313 1.340 1.276 1.272 1.173 1.188 1.169 1.226 1.275 1.328 0.052 

4 2.096 0.040 1.854 1.758 1.734 1.617 1.890 1.936 1.838 1.829 1.690 1.719 1.671 1.766 1.837 1.913 0.054 

5 1.031 0.029 0.912 0.850 0.844 0.795 0.940 0.931 0.900 0.895 0.889 0.852 0.854 0.888 0.047 

6 2.061 0.036 1.856 1.692 1.696 1.590 1.900 1.868 1.804 1.803 1.785 1.716 1.699 1.771 0.051 

7 2.909 0.023 2.788 2.519 2.521 2.363 2.825 2.783 2.696 2.696 2.652 2.568 2.523 2.625 0.052 

8 3.901 0.093 3.712 3.360 3.371 3.173 3.786 3.721 3.595 3.602 3.573 3.428 3.372 3.502 0.052 

9 0.183 0.078 0.175 0.174 0.170 0.163 0.169 0.180 0.189 0.185 0.187 0.180 0.169 0.188 0.049 

10 0.722 0.125 0.637 0.583 0.580 0.578 0.613 0.654 0.667 0.637 0.633 0.608 0.595 0.638 0.049 

11 1.772 0.020 1.554 1.405 1.385 1.389 1.482 1.582 1.598 1.528 1.524 1.458 1.425 1.539 0.051 

12 2.146 0.027 1.853 1.666 1.650 1.652 1.762 1.890 1.907 1.822 1.813 1.740 1.693 1.839 0.052 

Average 

gravimetric 

RSD 0.049 Average PDM RSD 0.051 1

Test run in group 2. 

 

Accuracy 

The premine test results support the thesis that design changes made between the prototype 

PDM–1 and the precommercial 3600 PDM did not affect the accuracy of the instrument. Results 

from the pre- and postmine calculation of accuracy, bias, precision, and 95% upper confidence 

limits (UCLs) are shown in Table 4. The bias results show that the PDM reads consistently less 

than the gravimetric reference mass measurement. Pretest bias, as received from TEC, was 

measured to be 5.2%. Despite the bias, high precision enables the point estimate of accuracy to 

meet the ±25% criterion. However, there were occasions for both the pre- and posttesting when 

the results failed to meet the 95% UCL that the PDMs are within ±25%. Failure of an instrument 

to meet the 95% UCL but to not exceed a 5% CL (failure to meet criterion) results in the 

decision that the accuracy determination for those samplers is inconclusive. Of particular note 

for the postmine testing was that bias values greater than –0.13 were associated with all 

instruments that did not meet the 95% UCL for reasons to be discussed. 

20
 
Table 4.—PDM pre- and postmine lab accuracy calculations 

Premine lab tests Postmine lab tests 

PDM 

No. Bias 

Upper 95% 

Precision Accuracy confidence Bias Precision Accuracy 

limit 

Upper 95% 

confidence 

limit 

102 .......... –0.04 0.05 12 18 –0.10 0.02 12 14 

105 .......... –0.08 0.07 18 26 –0.10 0.03 13 16 

108 .......... –0.09 0.05 16 21 –0.13 0.02 15 17 

109 .......... –0.05 0.06 14 20 –0.16 0.05 22 27 

110 .......... –0.06 0.03 11 15 –0.16 0.05 23 27 

111 .......... 0.00 0.04 8 11 –0.20 0.04 25 28 

112 .......... –0.03 0.03 7 10 –0.01 0.03 5 8 

113 .......... –0.07 0.05 14 19 –0.09 0.01 10 11 

114 .......... –0.08 0.04 13 18 –0.18 0.02 20 22 

115 .......... –0.08 0.06 17 22 –0.11 0.02 14 15 

116 .......... 0.00 0.04 7 11 –0.10 0.05 16 21 

119 .......... –0.02 0.05 10 15 –0.07 0.02 9 11 

120 .......... –0.06 0.04 12 16 –0.04 0.03 8 11 

122 .......... –0.04 0.05 11 16 –0.07 0.02 11 13 

123 .......... –0.01 0.03 7 10 –0.05 0.02 8 10 

124 .......... –0.10 0.04 16 20 –0.06 0.01 7 7 

125 .......... –0.01 0.07 14 21 –0.03 0.06 12 18 

126 .......... –0.06 0.03 10 14 –0.09 0.04 15 20 

127 .......... –0.06 0.05 14 20 –0.05 0.02 8 10 

128 .......... 0.01 0.02 4 6 –0.08 0.02 11 12 

130 .......... –0.01 0.07 13 20 –0.11 0.04 17 21 

131 .......... –0.09 0.04 14 18 –0.13 0.07 22 28 

132 .......... –0.02 0.03 7 10 –0.15 0.05 22 26 

133 .......... –0.18 0.04 22 25 –0.17 0.04 22 25 

135 .......... –0.04 0.07 16 24 –0.12 0.05 19 24 

Even though some of the units’ postmine sampling accuracy results were inconclusive, the mean 

accuracy values of pre- and postmine testing are statistically equal. Results from an independent 

samples t-test show mean accuracy (premine) was 12.27 (95% CL = 10.52, 14.03) and postmine 

was 14.67 (95% CL = 12.21, 17.08) (t-value (df = 48) = –1.63, p-value = 0.11). The null 

hypothesis that the mean premine accuracy is equal to the mean postmine accuracy was not 

rejected. 

One PDM failed to meet the 95% UCL of accuracy during the premine testing and was returned 

to the factory for examination and recalibration. We were unable to verify that the factory’s 

recheck restored accuracy; consequently, this unit was not used for underground precision 

determination. However, the postmine verification testing showed that the sampler in question 

was within the accuracy criterion. 

Calibration Constant K0 

We investigated why some instruments did not meet the posttest 95% UCL. Table 5 presents the 

results of the laboratory measurement of the constant factor (K0) that the instrument uses to 

calculate mass from the change in frequency of the TE. The RSD of replicate measurements of 

K0 conducted with two of the instruments was 0.0038 and 0.0027. 

21
 
Table 5.—Comparison of PDM measured K0 and programmed K0 

Unit 

No. 

Premine lab tests Postmine lab tests 

Measured 

K0 

Programmed 

K0

K0

difference, 

%

Upper 95% Accuracy, confidence % limit Upper 95% Accuracy, confidence % limit 

119........... 10 15 9 10 15368 15427 –0.4 

127........... 14 20 8 9 15138 15552 –2.7 

112........... 7 10 5 8 15827 16028 –1.3 

112........... Rep Rep Rep Rep 15719 16028 –2.0 

112........... Rep Rep Rep Rep 15724 16028 –1.9 

110........... 11 15 23 27 15166 15284 1.14 

131........... 14 18 22 28 15138 14827 2.1 

133........... 22 25 23 26 15107 14361 4.9 

132........... 7 10 22 26 14534 13846 4.7 

132........... Rep Rep Rep Rep 14537 13846 4.8 

132........... Rep Rep Rep Rep 14466 13846 4.3 

Rep Replicate K0 measurement. 

 

 

We compared the K0 factor for units with higher and lower posttest accuracy. For three PDMs 

with lower or better UCL accuracy during the postmine testing, the programmed K0 was within 

2.7% of the measured K0. However, for four of the PDMs that did not meet the postmine test 

UCL accuracy (i.e., higher), the difference in the measured K0 from programmed K0 showed a 

reduction by as much as 4.9%. Further investigation of the data file logs also indicate that, for 

some of the PDM units, the programmed K0 factor was changed by the factory between the preand posttesting when the units were returned for repair. Not all units needed this recalibration. 

However, any instrument that had a repair in the TE module (i.e., temperature sensing) may have 

required the K0 to be recalibrated. Because the constant is directly proportional to mass, this 

recalibration may be one reason why the postmine testing did not meet the 95% UCL for 

accuracy. Bias introduced by the calibration constant may cause some of the inaccuracy 

observed. 

Limit of Detection and Quantification 

The traditional limit of quantification (LOQ) [Marple and Rubow 1983] required determining the 

standard deviation of weighing (SW) in nine consecutive weighings of a blank filter. Both 

balances were determined, coincidentally, to have an SW of 1.4 μg and a resultant LOQ of 14 μg 

in a single weighing. However, quality control procedures involving control room filters used 

only in the balance room document that the total standard deviation (ST) due to SW and the cyclic 

fluctuations in weigh room conditions during the course of this study resulted in an ST of 4.1 μg. 

Applying traditional formulas for propagation of error in the filter dust weight gains, we obtained

 Sfilter = 2ST = 8.2 μg (5) 

The factor 2 results from the fact that there are four weighings required to determine the mass 

gain of the sample: the pre- and postweighing of both the sample and the control filter average. 

Similarly, for the calculations derived from the impactor, given that there are nine stages 

involving 36 weighings, we obtained 

Simpactor = 6SΤ = 24.6 μg (6) 

22
 
Battery Depletion Effects 

There was no detectable effect on instrument accuracy, as batteries were intentionally run to 

failure. The frequency measurement by the TE was unaffected by small drops in battery voltage. 

Comparing the mass accumulation rate of an individual PDM with a corresponding TEOM 

1400a, there was no change in the slope as batteries failed. The most significant effect measured 

as battery power failed was the decreased flow associated with the pump. Figure 5 shows that 

the flow diminished from full nominal flow rate of 2.2 L/min ± 5% to 0 L/min in less than 2 min. 

The resulting change in the cyclone classification as a result of the low flow condition 

represented about 0.3% of an 8-hr sample time. The data also showed that one instrument failed 

518 min into the test. The battery charger cable to this instrument was faulty and was replaced 

prior to additional testing. 

23
 

Flow rate, L/min

2.3 

2.2 

2.2 

2.1 

2.1 

2.0 

2.0 

1.9 

0 100 200 300 400 500 600 700 800 900 

TIME, minutes 

113 

112 

115 

126 

128 

132 

PDM # 115 stopped after 512 minutes due to a 

defective battery charger cable. After 

replacing the cable and charging, PDM #115 

ran for 720 minutes. 

Legend 

Figure 5.—Battery testing to failure using flow rate as an indicator. 
Detailed In-mine Testing 

Performance Over Project Duration 

Testing was conducted from November 2004 to August 2005. Results in Table 6 show the total 

number of PDM samples taken in each of the MSHA districts sampled, the number of valid 

samples recorded, the percentage of valid samples, and a breakdown of whether NIOSH 

personnel were present or absent on the property. Valid concentration data for each occupation 

at each of the detailed mine sites are in Appendix A. The data were collected during typical 

mining operations, and data collection was not associated with any type of negative 

consequences for the mines. The data represent an overall performance rate of the software, 

electrical, mechanical, and physical subsystems of the PDM. At the first mine site, a significant 

error in the internal instrument software resulted in multiple errors and an instrument availability 

for valid data collection of 51%. All instruments were returned to the manufacturer for 

reprogramming. Subsequent testing proceeded with average instrument availability of 93%, 

ranging between 86% and 97%. 

Table 6.—Total samples taken during detailed mine sampling and number of valid samples 

when NIOSH was present or absent from the mine property 

NIOSH present NIOSH absent MSHA No. No. No. No. district % valid % valid samples valid samples valid 

DETAILED MINE TESTING 

9.............. 31 17 55 64 31 48 

No. 

samples 

95 

Total 

No. 

valid 

48 

% valid 

51 

3.............. 30 29 97 37 33 89 67 62 92 

4.............. 27 22 81 45 40 89 72 62 86 

11............ 40 39 98 64 59 92 104 98 94 

2.............. 36 34 94 60 53 88 96 87 91 

10............ 35 35 100 68 63 93 103 96 93 

6.............. 30 28 93 30 28 93 

5.............. 33 32 97 33 32 97 

8.............. 38 37 97 38 37 97 

7.............. 23 22 

2(1).......... 

9(1).......... 

2(2).......... 

9(2)a......... 

9(2)b......... 

1

For the extended mine testing w

district 9, company 2 sampled at 

96 23 

EXTENDED MINE TESTING1 

 9 4 44 9 

 22 20 91 22 

 26 23 88 26 

 7 7 100 7 

 9 3 33 9 

ithin MSHA districts 2 and 9, each district had two companies ("

two mines ("a" and "b"). 

22 

4 

20 

23 

7 

3 

96 

44 

91 

88 

100 

33 

1" and "2"). Within 

After testing at the sixth mine site, the percentage of valid samples with NIOSH present or 

absent showed little difference. NIOSH, in consultation with the PDM Partnership, concluded 

that the remaining detailed mine testing did not require the second week of testing, and the 

remaining detailed mine site testing was conducted for only the one week with NIOSH present. 

Testing concluded in May 2005, followed by a period of extended mine testing. 

24
 
Extended Testing 

A period of extended mine sampling was conducted from June to August 2005. Results of 

instrument availability in Table 6 are similar, but more variable than the previous detailed mine 

results. This was caused primarily by one PDM at mine 2(1) and another PDM at mine 9(2)b 

that failed for the entire trial periods, where mine staff were untrained to recognize such 

problems. Consequently, mine staff continued to run instruments that normally would not have 

been used. The problem with each instrument was, however, obvious when downloaded data 

files were examined. 

Feedback from the miners using the PDM during the extended mine testing was consistent with 

the feedback received during the detailed mine testing, although not all mines provided written 

feedback to NIOSH. Comments from miners are in the “Discussion” section of this report. 

A new issue raised during this testing was that the side entry of the power cord into the cap lamp 

was not compatible with the flip clip used on the personal air purifying respirators in use at one 

mine. The flip clip relies on the in-line tension of the cap lamp power cord to maintain the light 

position when the face shield is raised. The side entry of the PDM cap light creates an offbalance situation. 

Maintenance Results 

The 25 precommercial PDM instruments logged 10,926 hr of testing, of which 8,023 hr were 

conducted underground. The average logged use per instrument was 437 hr, with a maximum of 

644 hr and a minimum of 246 hr. Hours of use varied based on the type of sampling for which 

each particular unit was used. The earliest repair episodes before the firmware upgrade were not 

counted in final PDM repair summaries, as they were regarded only as factory adjustments to the 

released product. 

Table 7 presents the summary of PDM use and repair. Each PDM unit is listed with actual total 

hours and categorized repairs. Total repair rates and critical repair rates per 1,000 hr of projected 

instrument use are presented in the table. Data for individual PDMs are ordered first by best 

critical repair rate and next by best total repair rate. The 25 PDMs are divided into quintiles of 

5 PDMs each, with best repair rates at the top of the table. Summary averages are recorded by 

quintile groups and also for the full set of all 25 PDMs. 

Repair frequency varied among the precommercial PDMs. Those in the top two quintiles needed 

little service, while those in the bottom two quintiles required more repairs by the manufacturer. 

The bottom quintiles required both remedial and critical repairs, while the top quintiles only 

required repairs of a remedial nature. The PDM instruments in the top quintile averaged 506 hr 

of use without needing a critical repair. Their ultimate reliability could not be calculated because 

no critical repairs were required for them over the full timespan of the project. 

Table 8 presents the summary of PDM run success rates for all PDM sampling. Each PDM unit 

is listed with its count of total runs and successful runs. An invalid run can be caused by human 

error, such as poor filter placement, in addition to a mechanical failure. Data are ordered by best 

success rate, with highest percentage rates at the top of the table. Data are again organized by 

25
 
quintile groups, with summary data for all 25 PDMs also recorded. The overall average success 

rate was 90.18% based on 1,202 total runs. The run success rates for the top two quintiles 

ranged from 92.42% to 100.00%. Data from Tables 7–8 are independent assessments of 

instrument reliability. Consequently, repair rates do not correspond to run success rates in part 

because of researcher intervention to prevent accumulation of unsuccessful samples. In addition, 

the causes of failed runs were often minor and readily correctable without manufacturer repair. 

26
 

Table 7.—Summary of PDM use and repair by quintile 

PDM No. Total 

repairs 

Remedial 

repairs 

Critical 

repairs 

Total 

hours 

run 

Total 

repairs/ 

1,000 hr 

Critical 

repairs/ 

1,000 hr 

111.................................... 

114.................................... 

135.................................... 

126.................................... 

130.................................... 

 Means ............................ 

1 

1 

1 

1 

1 

1.00 

1 

1 

1 

1 

1 

1.00 

0 

0 

0 

0 

0 

0.00 

612.25 

512.00 

505.00 

482.25 

418.50 

506.00 

1.63 

1.95 

1.98 

2.07 

2.39 

2.01 

0.00 

0.00 

0.00 

0.00 

0.00

0.00 

125.................................... 

124.................................... 

115.................................... 

116.................................... 

127.................................... 

 Means ............................ 

1 

1 

1 

2 

1 

1.20 

1 

1 

1 

2 

1 

1.20 

0 

0 

0 

0 

0 

0.00 

392.50 

390.75 

315.25 

581.25 

246.00 

385.15 

2.55 

2.56 

3.17 

3.44 

4.07 

3.16 

0.00 

0.00 

0.00 

0.00 

0.00

0.00 

112.................................... 

120.................................... 

131.................................... 

128.................................... 

133.................................... 

 Means ............................ 

2 

2 

2 

3 

2 

2.20 

2 

2 

2 

3 

1 

2.00 

0 

0 

0 

0 

1 

0.20 

445.75 

416.25 

384.50 

328.25 

643.75 

443.70 

4.49 

4.80 

5.20 

9.14 

3.11 

5.35 

0.00 

0.00 

0.00 

0.00 

1.55

0.31 

102.................................... 

122.................................... 

123.................................... 

105.................................... 

113.................................... 

 Means ............................ 

2 

3 

2 

2 

3 

2.40 

1 

2 

1 

1 

2 

1.40 

1 

1 

1 

1 

1 

1.00 

581.00 

515.25 

408.25 

406.00 

399.25 

461.95 

3.44 

5.82 

4.90 

4.93 

7.51 

5.32 

1.72 

1.94 

2.45 

2.46 

2.50

2.22 

119.................................... 

132.................................... 

110.................................... 

109.................................... 

108.................................... 

 Means ............................ 

2 

3 

4 

3 

3 

3.00 

1 

2 

3 

1 

1 

1.60 

1 

1 

1 

2 

2 

1.40 

383.50 

373.00 

361.00 

503.50 

321.25 

388.45 

5.22 

8.04 

11.08 

5.96 

9.34 

7.93 

2.61 

2.68 

2.77 

3.97 

6.23

3.65

 Summary means......... 1.96 1.44 0.52 437.05 4.75 1.24 
Table 8.—Overall success rate by quintile 

PDM 

No. 

Total 

count 

No. 

valid 

% 

valid 

131...................... 42 42 100.00 

135...................... 56 55 98.21 

108...................... 36 35 97.22 

127...................... 33 32 96.97 

105...................... 43 41 

 Mean................................................ 

95.35

97.55
 

126...................... 49 46 93.88
 

116...................... 61 57 93.44
 

125...................... 45 42 93.33
 

114...................... 55 51 92.73
 

111...................... 66 61 

 Mean................................................ 

92.42

93.16
 

132...................... 39 36 92.31
 

102...................... 64 59 92.19
 

112...................... 51 47 92.16
 

128...................... 33 30 90.91
 

119...................... 39 35 

 Mean................................................ 

89.74

91.46
 

123...................... 47 42 89.36
 

122...................... 56 50 89.29
 

115...................... 42 37 88.10
 

133...................... 70 61 87.14
 

109...................... 54 47 

 Mean................................................ 

87.04

88.18
 

130...................... 46 40 86.96
 

110...................... 37 31 83.78
 

120...................... 46 38 82.61
 

124...................... 45 36 80.00
 

113...................... 47 33 

 Mean................................................ 

70.21

80.71
 

 Total.............. 1,202 1,084
 

 Mean............................................. 90.18
 

Underground Precision 

Statistical results from the ANOVA in Table 9 show RSDs of the instruments in the Lippmann 

chamber used in the detailed mine sampling. All data used in this analysis are in Appendix B. 

The PDM had an RSD of 0.078 with a 95% CL of 0.066–0.095. Kissell and Sacks [2002] state 

that for normally distributed data, a 25% accuracy criterion is met with an RSD of 0.125 or less. 

The CMDPSU at a flow rate of 2.0 L/min had an RSD of 0.052, which can be compared to 

previous work by Kogut et al. [1997] where an RSD of 0.046 was determined for the same 

sampler at weight gains of greater than 0.5 mg/m3. The higher RSD of 0.082 for the CMDPSU 

at a flow rate of 1.7 L/min is caused by a few influential samples that looked anomalous, but had 

no physical reason to be excluded from the data set. 

27
 
Table 9.—Field precision results 

Instrument No. of

samples RSD 95% CL 

PDM...................................................... 88 0.078 .066–.095 

CMDPSU: 2.0-L/min flow rate.............. 89 0.052 .044–.063 

CMDPSU: 1.7-L/min flow rate.............. 90 0.083 .070–.101 

DISCUSSION 

Instrument Bias 

Mass measurement is determined by the PDM using first principles of physics according to 

equation 1. Theoretically, therefore, we would expect mass measurement based upon this to be 

unbiased. However, with many electronic instruments we can measure a systematic discrepancy 

between the mean of the distribution of measurements and the true mass being measured. This 

bias was determined for the PDM and, according to Bartley et al. [2003], a bias correction can be 

made and the expanded uncertainty and accuracy limit can be equivalent to the original 

determinations. Adding a bias correction to the PDM mass measurement will further improve 

the accuracy of the instrument. 

At the outset of this work, certain technical tradeoffs were made to make the measurement of 

coal mine dust exposure both functional and accurate. One acknowledged tradeoff is the loss of 

respirable dust in the tube from the cap light to the cyclone. This source of loss was minimized 

through the use of conductive tubing, which minimized electrostatic losses, and by the use of an 

optimized transport velocity. Peters and Volkwein [2003] calculated and measured this loss to 

be about 2% of the total respirable fraction. Another source of particle loss may occur in the 

heater between the cyclone and PDM filter. This has not been quantified directly, but is a part of 

the overall measurement of bias. The measured bias of the PDM is negative and thus consistent 

with the physical loss of a small amount of particulate mass in the transition zone between the 

cyclone and filter. This loss will be variable depending on the respirable size distribution of the 

dust. Results from both the laboratory and the detailed testing in this work indicate that various 

particulate losses within the PDM are trivial. The technical tradeoffs made to create a more 

functional instrument have had a minimal impact on instrument comparison to established 

sampling techniques. 

The cause of the increase in the bias of the postmine accuracy verification testing may have 

arisen from three separate or combined sources. The first is the K0 calibration value differences. 

These are associated with high bias values of some but not all of the instruments. Secondly, the 

manufacturer discovered that the gasket between the cyclone and PDM could expand (creep) into 

the airway area, disrupting the flow and likely causing particulate loss. Finally, it was observed 

in one of the units that did not meet the 95% UCL that a sealant had contaminated the conical 

cyclone outlet, which would contribute to the creation of turbulence and particulate loss. 

Regardless of the cause, periodic calibration, inspection, and cleaning of the instrument 

are advisable. 

28
 
Precision 

It has been suggested that the field precision of the PDM should be adjusted to account for 

instruments that may be delivered from the manufacturer that did not meet the initial NIOSH 

accuracy criterion. The logic for this adjustment is that most users would be unable to detect 

such flaws and that this would actually be a contributing factor in the precision calculation. 

The adjusted RSD would be calculated from 

⎛ n RSD ⎞⎞

RSDnew =
 ⎜RSD field +
 fail ⎛

⎜ field ⎟⎟ ⎜ ⎜ ⎟ ⎝ 100n ⎟

total ⎝ RSDlab ⎠⎠ (7)

Only one PDM failed to meet the initial 95% UCL accuracy criterion. The high precision 

of the lab measurements results in a small change of field precision from 0.0780 to 0.0786. 

Furthermore, these first instruments were in the precommercial stage of production, and one 

might expect the manufacturer’s quality control to improve with experience, further reducing 

this impact on the field precision. Therefore, the suggestion that field precision be adjusted is 

not merited. 

Training and Comments 

Training sessions on how to use the PDM at each mine were 30–45 min long. This training was 

important not only to ensure that miners knew how to use the PDM, but also to offer the 

opportunity for NIOSH to address miners’ concerns and objections. Miners were encouraged to 

provide their opinions and feedback on their experience with the PDM. 

A key feature of the PDM is that it be suitable for use by miners. In addition, miners for the first 

time have a timely way of accurately knowing the dust levels in their work environment. During 

the course of the study, NIOSH had an opportunity to informally listen to miners’ opinions about 

the PDMs while they were wearing and working with the units. This part of the discussion 

relates anecdotes recorded by the researchers during the testing. The initial reaction to the PDM 

during the introduction and training session of the detailed mine visits was one of skepticism and 

doubt about the size, weight, cap light, and overall benefit of the instrument. By the end of 

the detailed mine testing, most miners felt that they would prefer their dust monitoring to be 

done with the PDM mainly because it did not interfere with their work in the way the current 

sampler does. 

The reaction of miners varied from total disinterest, where they treated the PDM just like their 

cap lamp, to active involvement, where they were correlating what they were doing with what 

the instrument was telling them. One miner operator said that he glanced at the display after 

every shuttle car of coal. The data from the PDM offered some surprises to the miners. Some 

roof bolters expressed surprise that they were “getting dust when they could not see it.” A rock 

duster said he was surprised that his levels were so low when conditions appeared particularly 

dusty. Most of the miners who paid attention to the PDM thought it was a useful tool. One 

29
 
foreman used the results of the shuttle car operators to vary the haulage routes to minimize 

exposures. 

There were several comments that the curved design of the PDM offsets the slight increase in the 

weight of the unit over the weight of the lead-acid cap lamp batteries currently used by all of the 

mines in these trials. One complaint, particularly by the mechanics, was that the PDM was 

bulkier than the lead-acid batteries and that there was less room for tools on the belt. Miners 

commented that the quality and brightness of the cap lamp was good, but many did not like the 

nonfocusable lens system, particularly if the light was not focused correctly. Miners generally 

preferred the old-style, full-size backup bulb in the cap light over the white light-emitting diode 

(LED) lamp in the PDM. One mine suggested that the LED bulb should be green to help see in 

smoke. Unlike feedback during the prototype testing, there were few complaints about the noise 

of the pump. Workers in outby areas were more likely to comment about the noise than face 

workers. Noise was more noticeable during dinner break, but not objectionable. The pump 

outlet that produces most of the noise is highly directional and easily muffled with a coat without 

affecting the flow. Frequent complaints were made that the cap lamp cord was too long. The 

longer-length cord was selected for these trials to ensure that the length would accommodate the 

largest miners. In fact, when shorter cords were installed for the extended mine testing, 

complaints resulted that the cords were too short. Cord length of production units should be 

easily exchangeable. Another complaint about the cords was that they were stiff and chafed the 

necks of miners in warmer mines. 

Screen Presentation of Data 

The data display screens, shown in Figure 6, show the miner his or her exposure data in different 

formats. Miners responded differently to this information. Some found value in the graphic 

format; others preferred one of the numeric formats. The nomenclature used to describe of each 

of the numeric formats caused confusion. Based on observations in this testing, the cumulative 

concentration (CUM0), which is mathematically the mass divided by volume sampled to this 

point in time, becomes a good predictor of the EOS concentration about midway through the 

shift, provided that conditions do not change. On the other hand, the projected concentration 

(PROJ), which is mathematically the mass divided by the volume to be sampled for the entire 

shift, is not a direct estimate of a miner’s EOS concentration. Perhaps a better name for this 

value is “limit concentration.” Regardless of the name, the worth of the “PROJ” value is that it 

will not fluctuate with changes in the concentration; rather, it steadily progresses to the true EOS 

concentration. If CUM0 exceeds the permissible exposure limit (PEL), steps can be taken to 

reduce the exposure to stay within the PEL before the EOS. Once the limit (PROJ) is exceeded, 

it becomes impossible to meet the PEL. Despite the apparent confusion in nomenclature, miners 

watching the screens quickly learned to identify the meaning of the various formats in relation to 

their activities. 

30
 
 Figure 6.—Basic PDM screen display formats and information presented. Left: graphic format; 

right: numeric format. 

Performance Issues 

During mine testing, small engineering and operational issues occurred that may have affected 

the availability of the instrument for use or were reported as a nuisance by the miners. Table 10 

reports those issues and steps taken to resolve them. As with any new system, especially those 

used by miners in the challenging underground environment, operational issues such as these 

will only be discovered through use of the device. The introduction of the currently used 

CMDPSU into the mining industry underwent several years of issue discovery and problemsolving until the technology matured. The testings of the prototype and the current 

precommercial PDM have probably not identified all of the possible issues with this new 

technology, but hopefully have helped shorten the time in which full maturity will be reached. 

31
Table 10.—PDM performance issues and comments 

Performance issue Comments 

Control of TE temperature...................................... Resolder connection of temperature sensor; heater was OK.
 

Display malfunction................................................ Poor quality control from supplier; hired new supplier – 

 replaced all keypads or fuses.
 

Button malfunction ................................................. Part of display assembly replaced.
 

PDM failed to communicate to computer ............... Software/firmware bug fixed by TEC after first mine trial.
 

Battery failure ........................................................ Replaced battery.
 

Premature cap lamp bulb failure ........................... Reengineer filament thickness. Resubmit for MSHA approval.
 

Flat line in data file ................................................. Intermittent problem; unresolved – possible incorrect filter 

placement. 

Low power.............................................................. Associated with charging problems; bad battery cell or 

 insufficient charging. 

Charger problem, contacts give false indication Clean contacts, design contacts to be self-cleaning. Improve 

of charge status. charger-sensing firmware.
 

High filter load at start of test.................................. Incorrect filter placement.
 

Broken cyclone inlet ............................................... Add better strain relief at inlet.
 

Cut tube at cyclone inlet......................................... Add better strain relief at inlet.
 

Bad focus on cap lamp........................................... Reshim bulb; instruct technician on focus procedures.
 

TE not detected...................................................... Design tighter TE connection.
 

Failed leak checks.................................................. Connection between cyclone and PDM leaks; resealed with 

 silicone grease, needs redesign. 

Incompatible with new remote controls .................. TEC to redesign power output cable of PDM to remote to be 

 compatible with new devices. 

Cable to cap lamp too long or too short ................. TEC to offer alternative lengths or be capable to field retrofit. 

Data Files 

Download 

When WinPDM software is used to download data from the PDM to the computer, several 

options are available to the user. The first option is to print a “dust data card” (Figure 7), which 

looks similar to the currently used dust data card, but contains the final EOS exposure of the 

instrument and any error codes recorded by the instrument. In this case, the actual exposure was 

0.73 mg/m3

. The instrument currently reports how each sample was terminated in the error code 

field. In this example, a normal “Program end of sample” message appears in the error code 

field. Since normal termination of a sample is not an error, this message is inappropriate for that 

field. The next option during downloading is to visually examine graphs of various parameters 

such as concentration, mass, flow, pressure, or tilt versus time. This option was not frequently 

used in this testing, but was useful to provide a quick summary of the day’s events. Finally, the 

data can be saved by the computer in a comma-separated version (.CSV) text file for archiving or 

more detailed examination using common spreadsheet software. 

32
 
 Figure 7.—Example of data printout. (MMU = mining machine unit. DA = designated area. SA = surface area.) 

33 
Interpretation 

Data graphs can be constructed from the text files. Figure 8 shows the results of a plot of the 

data created from a saved file associated with the dust data card from Figure 7. These data 

illustrate the effect of a short-term dust spike at 9:00 on the cumulative and projected dust 

concentrations. The cumulative concentration decreases after the spike, but the projected 

concentration continues to increase. At the end of the shift, the cumulative and projected 

concentrations are equal. 

34
 

0 

0.5 

1 

1.5 

2 

2.5 

3 

3.5 

4 

4:48 6:00 7:12 8:24 9:36 10:48 12:00 13:12 14:24 

Time 

Concentration (mg/m3)

30 Min 

Cumulative 

Projected 

Figure 8.—Detail of results from sample shown in Figure 7. 

Error Codes 

Meaning and Interpretation 

The PDM automatically senses and has the capability to report many useful instrument and 

environmental parameters. These parameters may be selected by the factory or authorized user 

and can be stored in memory with the frequency or change interval desired. TEC provides a 

basic template or digital file of instrument-controlling parameter settings, in addition to a 

diagnostic template for troubleshooting the device. Templates may be configured to report error 

flags at various sensitivities and time intervals. 
Distinguishing Valid Data 

How these error code parameters are set to distinguish valid from invalid samples is an important 

question. The criteria for selecting the validity of a sample will ultimately lie with the end use of 

the instrument. A difference between the prototype and precommercial PDM was the way in 

which errors were determined. The original thinking to distinguish sample validity was to use 

the tilt sensor to determine if the instrument was inverted and if this action dislodged oversize 

particles from the cyclone grit pot onto the mass sensor (a rare occurrence based on the data in 

Appendix C). Prototype results indicated that this was not a reliable method since it gave 

frequent false indications. In addition to being nonrespirable, oversize particles invalidate a 

sample under the current system because they result in an excessive, instantaneous mass increase 

to the filter. As an alternative to using the tilt function, a new algorithm was written for the 

precommercial PDM in which the rate of filter mass increase would result in a mass offset (MO) 

error being reported. Thus, the result of the tilt event—oversize particles changing the mass on 

the filter—rather than the event itself becomes the reason for invalidating a sample. 

In this testing, the MO sensitivity settings were initially set to report an error when the mass 

loading increased by 50 μg over a 2-min time interval. At this setting, MO errors were 

frequently reported when in fact valid data were being recorded, such as when entering a return 

airway. This setting was changed after the second mine trial to only report errors when a level of 

100 μg over a 1-min time interval was sensed. This change greatly reduced the frequency of MO 

errors. However, valid data were still being reported as an error, and an even higher mass 

loading setting is probably warranted. 

In addition, when the sample inlet tube is pinched closed, the resulting sudden decrease in 

pressure in the TE environment is sensed and is reported as a rapid change in mass, resulting in 

an MO error. This is evident in Figure 9 where the differential pressure and mass are plotted. 

Note that when the pinch is relieved, the mass returns to the original level so that the EOS 

concentration measurement is unaffected by the event. Also note that these pinch events may 

momentarily reduce the flow rate of the instrument. With this information, the manufacturer 

should be able to refine the MO algorithm to ignore events when a downward pressure spike 

occurs. If the resulting pinch continues for 2 min, a flow error will occur and the sample may be 

invalidated for that reason. Similarly, the algorithm could be refined such that if an MO event 

occurs in conjunction with a tilt event, then a tilt error could be recorded as the reason to 

invalidate a sample. 

35
 
0 

0.5 

1 

1.5 

2 

2.5 

7:12 8:24 9:36 10:48 12:00 13:12 14:24 15:36 16:48 

Time 

F lo w ra te (L /m in ) o r m a s s (m g ) 

-600 

-500 

-400 

-300 

-200 

-100 

0 

D iffe re n tia l P re s s u re (m m H g ) 

Flow rate 

Mass 

Differential 

pressure

 Figure 9.—Mass offset "error" resulting from pinched tube and subsequent recovery of correct 

mass measurements. 

MSHA currently uses a system of void codes to detect events such as those just mentioned. 

Analysis of MSHA data (Appendix C) for the 10-year period from 1994 to 2004 shows 

conventional filter sampling success (nonvoid) rates for inspector and operator samples of 92.3% 

and 83.1% on total samples of 381,335 and 487,713, respectively. Based on the type of void 

rates and the expanded capabilities of the PDM, we estimate that about half of the MSHA voided 

samples could have been valid samples using PDM technology. 

Maintenance 

Ongoing refinements to instrument design make remedial type of service, required in this study, 

less likely for future manufactured instruments. It is reasonable to expect that further 

refinements to design and manufacturing quality will ultimately cause all PDM units to perform 

in a manner consistent with the higher quintiles of these preproduction units once all issues 

related to minor design remediation and manufacturing practice are addressed. 

36
 
Calibration 

Flow 

PDM flow rates did not require frequent calibration. The initial flow calibration of each PDM 

occurred in late fall of 2004, when all units were returned to the manufacturer for firmware 

upgrades. Hours logged before this calibration are not included in this analysis. Recalibrations 

and hours logged are counted from the firmware upgrade service date onward. Two error 

standards for flow variance from the 2.2-L/min nominal flow rate were maintained for this 

testing. A ±1% standard was used for laboratory and precision testing, and a ±5% standard was 

used for the other detailed mine testing because this is the current allowable variance for 

CMDPSU sampling. Table 11 shows the calibration, flow error, and hours-logged histories for 

the 10 PDMs with complete flow calibration histories. Each PDM has an initial manufacturer 

flow calibration. A few units also experienced subsequent researcher recalibration of flow. Only 

one PDM required recalibration to maintain ±5% flow rate. Three PDMs were recalibrated to 

meet the more stringent ±1% calibration requirement for the research portion of the testing. 

A total of 3,354 hr were logged for the 10 units compiled in the table. 

Table 11.—Flow calibration history 

PDM 

No. 

1%–5% flow 

recalibration 

>5% flow 

recalibration 

Total hr 

run 

111................... 

114................... 

135................... 

126................... 

130................... 

125................... 

124................... 

115................... 

116................... 

127................... 

Totals............... 

0 

0 

0 

0 

0 

0 

0 

1 

0 

2 

3 

0 

0 

0 

0 

0 

0 

1 

0 

0 

0 

1

459.25 

455.50 

392.25 

321.75 

299.75 

339.25 

264.50 

204.25 

419.75 

197.75 

 3,354.00 

Hours per calibration to maintain ±1% flow............ 

Hours per calibration to maintain ±5% flow............ 

239.57
 

838.50
 

Currently, MSHA inspectors and mine operators calibrate flows for personal sampling pumps 

after each 200 hr of use. Although Table 11 cannot indicate a definitive timespan for scheduling 

periodic instrument flow calibrations, it does provide a reasonable range. For the 10 PDMs 

examined, approximately 240 hr occurred per calibration to meet a ±1% criterion and 

approximately 840 hr occurred per calibration to meet a ±5% criterion. Based on this 

information, flow calibration should occur between 240–840 hr. PDM flow stability is at least as 

reliable as current pumps and should not require more frequent calibration than current operator 

sampling procedures. 

37
 
 

Mass 

Routine laboratory measurement of mass requires that the balances be periodically calibrated to 

ensure the validity of the measurement. The PDM will likewise need to be periodically audited 

to ensure its legitimacy. The change in bias with use observed in this testing suggests that the 

calibration be done on a periodic basis; however, there are insufficient data to determine the 

calibration period. If a simple audit procedure can be implemented, it makes sense to perform 

this calibration check at the same time that the flow rates are checked. As more experience with 

the PDM is gained, this time period for checking mass calibration could be revised. 

CONCLUSION 

An accurate direct-reading dust monitor for use in coal mines has been demonstrated in 

laboratory and underground coal mine environments. Through a protocol developed by a 

partnership of labor, government, and industry, this work verified that the PDM laboratory 

accuracy met the criterion with 95% confidence that individual PDM measurements were within 

±25% of the reference measurements. In addition, accuracy after an extended period of mine use 

did not differ from the initial accuracy measurements. However, some individual units did 

exceed the 95% UCL after testing, and a shift in the bias of the instrument was a suspected 

cause. This leads to the recommendation that a periodic calibration check of the instrument mass 

measurement be considered in the operating procedures. 

Mine testing of the PDM, when worn by miners during normal work, demonstrated durable 

performance with about a 90% availability rate, which is similar to existing dust sampling 

devices. Many miners commented that they would prefer to use the PDM over the current 

sampler for dust measurements because of the integration of the sampler into the cap lamp that 

they normally wear. They further appreciated the immediate feedback of the screen-displayed 

exposure information. Some miners quickly learned to use the information to take action to 

minimize their exposures. 

Mine data demonstrated that the precision of the PDM operating in coal mines had an RSD of 

0.078. The final demonstration of equivalency to the MRE standard will be the subject of a 

subsequent publication. 

Future work includes how miners might make use of the data from the PDM to actually lower 

exposures. A study will be conducted to document how miners make use of the new dust 

exposure information they receive from their PDMs. Structured interviews will be conducted 

with approximately 50 miners representing each major category of underground mining job. 

Effective strategies for using PDM information will be documented, published, and shared 

throughout the coal industry. Although data were collected to measure the equivalency of the 

PDM to the MRE, as required by U.S. law, the analysis of these data was more complex than 

originally anticipated because the variance with increasing concentration required use of a more 

sophisticated statistical model than originally planned. Another publication containing a detailed 

analysis comparing the PDM samplers used in this work to MRE and ISO standards is 

in progress. 

38
 
ACKNOWLEDGMENTS 

The authors thank and acknowledge the support and technical advice provided by the joint 

Health and Safety Committee of the Bituminous Coal Operators’ Association and the United 

Mine Workers of America, co-chaired by Joe Lamonica and Dennis O’Dell, respectively. 

We also thank MSHA for its active support and participation in the collaborative research effort 

by purchasing units for testing and collecting vital test data at some 180 mechanized mining 

units around the country. We thank the individual mine managers for their hospitality and 

gratefully acknowledge the miners from the underground trials who worked hard to enable valid 

field data to be collected. We appreciate the generous engineering support provided by Erich 

Rupprecht, Business Development Manager, and Dan Dunham, PDM Project Manager, from 

Thermo Electron Corp. Finally, we thank Erica E. Hall, Calvin D. Garbowsky, Shawn E. 

Vanderslice, and Jeanne A. Zimmer of the NIOSH Pittsburgh Research Laboratory for their 

conscientious support in managing the logistics of the equipment for both the laboratory and 

mine measurements. 

39
 
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MSHA [2003]. Statement of David D. Lauriski, assistant Secretary of Labor for mine safety and 

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41
 
 

 

 

APPENDIX A.—DETAILED MINE PDM CONCENTRATION DATA
 

42
 

MSHA DISTRICT 9 

Date 

Occupation and MSHA code 

Shearer Mechanic Shearer Shift foreman Faceman Faceman Faceman Faceman Mechanic Headgate Dust sampler Fixed return Fixed return 

64 4 64 49 41 41 41 41 4 40 414 61 61 

Nov. 2 2.51 1.87 1.37 0.73 0.62 1.72 1.68 

Nov. 3 2.03 1.81 2.17 0.61 2.24 2.8 2.73 1.62 

Nov. 4 0.87 1.75 0.47 0.57 1.32 1.24 0.976 1.74 1.48 

Nov. 51 0.44 0.28 0.59 0.37 0.57 0.32 0.23 0.23 0.64 

Nov. 61 0.25 0.12 0.17 0.15 0.17 

Nov. 71 0.82 0.99 0.66 0.86 

Nov. 8 0.92 0.48 0.8 0.91 1.35 0.77 

Nov. 9 1.6 2.35 3.35 3.41 3.19 3.13 

Nov. 10 2.42 2.68 

Nov. 11 0.91 1.52 1.37 1.47 

1No production. 

MSHA DISTRICT 3 

Date 

Occupation and MSHA code 

 Miner 

operator 

Tube side 

bolter 

Intake side 

bolter 

Loader 

operator 

Standard Off-standard 

shuttle car shuttle car Mechanic Foreman Center bolter Center bolt 

helper 

36 48 19 43 50 73 4 430 46 47 

Dec. 14 0.38 0.69 0.31 1.09 0.26 0.37 0.35 0.5 0.35 0.33 

Dec. 15 0.55 0.49 0.54 0.41 0.28 0.33 0.32 0.93 0.6 0.46 

Dec. 16 0.48 0.72 0.45 0.37 0.26 0.31 0.4 0.45 0.54 

Dec. 17 0.37 0.31 0.35 0.35 0.33 0.36 0.4 0.92 

Dec. 20 0.69 0.57 0.44 0.33 0.36 0.4 0.48 0.07 

Dec. 21 0.32 0.39 0.27 0.24 0.3 0.19 0.72 0.87 

Dec. 22 0.31 0.41 0.4 0.24 0.24 0.19 0.23 0.66 ( 

2 ) 

2Cyclone broken, but ran in office. 

Shearer head Date operator 

064 

Jan. 4 0.84 

Shearer tail 

operator 

040 

0.66 

MS

Mechanic 1 

004 

0.66 

HA DISTRICT 4 

Occupation and MSHA code 

Mechanic 2 Jack setter 1 Jack setter 2 

004 041 041 

0.55 0.97 0.72 

Utility 

053 

0.7 

Foreman 

049 

0.79 

Jan. 5 1.41 1.07 0.69 1.4 1.29 1.3 

Jan. 6 1.52 1.53 0.57 0.8 1.58 1.69 1.07 1.2 

Jan. 7 1.4 0.64 0.56 0.66 1.43 1.33 1.13 1.71 

Jan. 10 1.47 1.53 1.36 0.85 1.54 1.51 1.27 1.63 

Jan. 11 1.86 1.84 0.25 1.02 2.07 1.56 1.42 1.88 

Jan. 12 0.85 0.75 0.59 0.13 1.01 0.97 0.96 0.77 

Jan. 13 1.45 1.44 1.05 0.85 1.21 1.24 1.07 1.56 

MSHA DISTRICT 11 

Date 

Occupation and MSHA code 

Miner 

operator 

36 

Miner helper 

35 

Intake side 

bolter 

12 

Return side 

bolter 

14 

Ram car 2 

50 

Ram car 3 Ram car 4 Foreman 

50 50 49 

Scoop 

54 

Curtain 

8 

Bratticeman 

32 

Outby intake 

bolter 

12 

Outby return 

bolter 

14 

Jan. 25 

Jan. 26 

Jan. 27 

Jan. 28 

Jan. 31 

Feb. 1 

Feb. 2 

Feb. 3 

 

0.73 

0.61 

0.58 

0.53 

0.5 

0.63 

0.77 

0.85 

1.23 

0.67 

0.95 

0.64 

0.78 

1.16 

1.35 

0.9 

0.65 

1.5 

0.51 

0.78 

1.06 

1.22 

2.63 

1.26 

0.9 

1.31 

0.43 

0.79 

1.05 

1.4 

1.65 

0.57 

1.17 

0.64 

0.7 

0.89 

0.32 

1.13 

1.05 

0.46 

0.98 

0.67 

0.6 

0.92 

0.27 

1.01 

0.69 

0.58 

1.16 

0.61 

0.58 

0.96 

0.36 

0.86 

0.86 

1.23 

1.01 

0.39 

0.59 

0.66 

0.96 

0.51 

0.92 

0.67 

0.88 

0.7 

0.65 

0.45 

1 

1.09 

0.58 

1.67 

0.41 

1.01 

1.53 

1.28 

0.66 

0.6 

0.64 

0.36 

 

1.3 

0.54 

0.64 

0.22 

0.68 

0.56 

0.49 

0.52 

1.43 

0.21 

0.52 

0.69 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 MSHA DISTRICT 11—Continued 

Date Occupation 

Guest Beltman Utility Motorman 

Jan. 25 

Jan. 26 

Jan. 27 

Jan. 28 

Jan. 31 

Feb. 1 

Feb. 2 

Feb. 3 

 

 

 

0.88 

0.48 

 

0.33 

 

 

0.84 

0.46 

 

0.57 
Date Standard 

shuttle car Center bolter Left return 

side bolter 

Off-standard 

shuttle car 

MS

Outby 

utilityman 

HA DISTRICT 2 

Occupation and MSHA code 

Center bolter Mechanic helper 

Miner 

operator Foreman Load machine 

operator 

Right intake 

side bolter 

Tubeman 

brattice 

Feb. 8 

50 

0.23 

46 

0.21 

14 

0.67 

73 

0.38 

53 

0.42 

47 4 

0.19 

36 

0.50 

49 

0.25 

43 

0.27 

12 

0.65 

32 

Feb. 9 0.14 0.19 0.55 0.21 0.19 0.17 0.19 0.41 0.31 0.18 1.74 0.86 

Feb. 10 0.42 0.4 0.78 0.25 0.48 0.24 0.31 0.42 0.31 0.89 0.73 

Feb. 11 0.18 0.25 0.23 0.29 0.41 0.30 0.40 0.45 0.27 0.51 0.64 

Feb. 14 0.22 0.20 0.79 0.16 0.24 0.21 0.43 0.29 0.22 0.66 0.55 

Feb. 15 0.15 0.24 1.63 0.29 0.21 0.19 0.38 0.52 0.87 0.58 

Feb. 16 0.24 0.26 0.82 0.42 0.04 0.26 0.34 0.39 0.42 0.63 0.93 0.96 

Feb. 17 

Date 

0.17 

Right miner 

operator 

0.18 

Left miner 

operator 

1.06 

Right bolt 

opposite 

operator 

0.28 

Right bolter 

operator 

MS

Left bolter 

opposite 

operator 

0.32 

HA DISTRICT 10 

Occupation and MSHA code 

Left bolter Shuttle car 1 operator 

0.54 

Shuttle car 2 

0.51 

Shuttle car 3 

0.41 

Shuttle car 4 

0.79 

Foreman 

1.17 

Mechanic 

Mar. 1 

36 

0.86 

36 

1.63 

12 

0.76 

14 

0.55 

12 

1.33 

14 50 

1.76 0.82 

50 

0.74 

50 

0.66 

50 

0.63 

49 

0.6 

4 

0.59 

Mar. 2 1.12 1.23 1.1 0.98 1.34 0.99 0.75 0.75 0.72 0.67 0.69 0.57 

Mar. 3 1.07 1.73 1.71 0.6 2.48 2.46 0.77 0.83 0.7 0.78 0.56 

Mar. 4 0.68 1.58 0.62 0.6 1.57 32.45 0.85 0.97 0.79 0.86 0.52 1.35 

Mar. 5 0.31 1.62 0.59 1.29 1.5 1.32 0.68 0.8 0.76 1.04 

Mar. 7 1.31 0.32 1.08 2.09 0.77 0.78 0.77 0.66 0.62 0.88 

Mar. 8 1.64 0.73 0.92 1.32 0.74 0.89 0.8 0.78 0.89 

Mar. 9 1.96 1.96 0.84 1 1.55 1.03 1.08 0.95 0.87 0.7 1.08 

Mar. 10 

3Data valid, voided for cause. 

0.67 1.64 0.7 312.12 36.32 0.75 0.76 0.53 

 

1.11 

MSHA DISTRICT 6 

Occupation and MSHA code 

Roof bolter Left miner Left bolter Right miner Right miner Date Shuttle car Electrician Shuttle car Foreman Left bolter Shuttle car operator operator operator operator operator 

12 36 50 2 14 36 50 49 12 50 36 

Mar. 15 1.57 1.53 0.66 0.29 1.9 1.08 0.26 0.82 2 0.23 

Mar. 16 1.22 1.7 0.9 1.47 1.65 0.56 1.75 1.7 0.52 0.98 

Mar. 17 1.14 1.6 0.52 1.68 0.34 0.71 0.33 1.16 

 

MSHA DISTRICT 5 

Occupation4 

Date Left bolter/ Right bolter/ Right bolter/ Left bolter/ Miner #1 Bridge Mechanic #2 Bridge MSHA Scoop #3 Bridge Foreman right side left side right side left side operator 

Mar. 29 1.42 1.25 0.63 0.58 1.19 1.31 NS 1.02 1.38 0.85 1.04 5.84 

Mar. 30 0.34 1.62 1.48 0.87 3.43 NS 3.52 3.01 1.61 2.18 1.26 1.63 

Mar. 31 0.32 0.72 0.5 1.17 NS 1.34 0.98 0.7 1.01 0.54 0.84 

NS Not sampled. 4MSHA code not available. 

MSHA DISTRICT 8 

Occupation and MSHA code 

Right miner Left miner Right intake Right return Left intake Left return Coal hauler Coal hauler Date Foreman Utility Mechanic Mechanic operator operator side bolter side bolter side bolter side bolter 67 69 

36 36 12 14 12 14 50 50 49 53 4 4 

Apr. 19 NS 1.61 0.95 2.92 1.64 1.6 1 1.19 1.37 1.05 

Apr. 20 NS 1.46 1.75 2.72 1.58 2.52 1.08 1.09 1.68 0.96 0.5 0.54 

Apr. 21 0.42 4.24 2.19 3.34 1.15 2.84 1.74 1.74 1.46 1.08 0.74 0.83 

 

MSHA District 8—Continued 

Occupation and MSHA code 

Coal hauler Date Safety 66

 50 

Apr. 19 0.72 1.6 

Apr. 20 0.69 1.27 

Apr. 21 NS NS 

NS Not sampled. 

 

MSHA DISTRICT 7 

Occupation and MSHA code 

Miner Pinner Standard Off-standard Date Electrician Scoop Foreman NIOSH 1 NIOSH 2 MSHA operator operator shuttle car shuttle car 

36 12 50 73 2 54 49 

May 17 0.35 0.24 0.29 0.24 0.34 0.23 0.17 0.47 

May 18 1.27 0.32 0.3 0.58 0.25 0.29 0.963 0.7 

May 19 1.01 0.6 0.26 0.28 2.67 0.27 

43 
APPENDIX B.—DETAILED MINE LIPPMANN SAMPLER DATA 

44 

Date PDM 

No. 

Conc. 

mg/m3 

PDM 

Avg. 

mg/m3 

Std. 

mg/m3 RSD Mass, 

mg 

Time, 

min 

Dorr-Oliver 2 L/min MRE 

equiv. Conc. Avg. Std. RSD conc. mg/m3 mg/m3 mg/m3 

mg/m3 

Mass, 

mg 

Dorr-Oliver 1.7 L/min 

Conc. Avg. Std. 

mg/m3 mg/m3 mg/m3 RSD 

Size distributions 

Inst. MMAD GSD No. 

TWENTYMILE MINE, MSHA DISTRICT 9 

Nov. 2 102 1.367 0.731 1.030 0.753 1.248 1 9.38 2.65 

122 1.475 1.397 0.068 0.049 0.750 355 1.056 1.046 0.014 0.013 1.443 0.711 1.178 1.228 0.044 0.036 2 9.35 2.51 

108 1.349 0.746 1.051 0.760 1.259 3 8.85 3.00 

Nov. 3 102 1.630 0.787 1.234 0.788 1.453 4 10.00 2.99 

122 1.771 1.662 0.097 0.058 0.788 319 1.235 1.204 0.052 0.043 1.662 0.777 1.433 1.432 0.021 0.015 5 7.13 2.58 

108 1.586 0.730 1.144 0.765 1.411 6 8.27 2.59 

Nov. 4 102 1.239 0.645 0.849 0.658 1.019 7 8.67 2.84 

122 1.307 1.215 0.106 0.087 0.664 380 0.874 0.842 0.036 0.043 1.161 0.667 1.033 1.010 0.027 0.027 8 7.48 2.57 

108 1.099 0.610 0.803 0.633 0.980 9 7.43 2.74 

BLACKSVILLE MINE, MSHA DISTRICT 3 

Dec. 14 115 0.365 0.059 0.271 0.062 0.335 7 8.68 2.34 

130 0.363 0.358 0.012 0.033 0.053 109 0.243 0.245 0.025 0.103 0.338 0.058 0.313 0.309 0.027 0.088 8 8.17 2.89 

135 0.344 0.048 0.220 0.052 0.281 9 8.19 3.06 

Dec. 15 115 1.506 0.614 1.023 0.679 1.331 10 6.56 2.59 

130 1.602 1.479 0.137 0.093 PF 300 1.045 0.031 0.029 1.442 0.636 1.247 1.252 0.077 0.061 11 7.32 2.90 

135 1.331 0.640 1.067 0.601 1.178 14 7.26 2.39 

Dec. 16 115 0.755 0.331 0.522 0.319 0.592 16 7.08 2.58 

130 0.826 0.764 0.058 0.076 0.342 317 0.539 0.515 0.029 0.057 0.710 0.314 0.583 0.622 0.060 0.096 17 7.53 2.57 

135 0.711 0.306 0.483 0.372 0.690 19 7.54 2.44 

HARRIS MINE, MSHA DISTRICT 4 

Jan. 4 115 2.655 0.954 2.129 0.866 2.273 1 5.49 2.83 

120 2.472 2.549 0.095 0.037 0.906 224 2.022 2.087 0.057 0.028 2.880 0.851 2.234 2.302 0.086 0.038 2 6.11 3.13 

135 2.519 0.946 2.111 0.914 2.399 3 5.34 3.02 

Jan. 5 115 1.988 0.447 1.519 0.413 1.651 4 6.06 2.92 

120 2.151 2.051 0.088 0.043 0.444 147 1.509 1.481 0.058 0.039 2.043 0.413 1.651 1.687 0.062 0.037 5 6.13 2.87 

135 2.013 0.416 1.414 0.440 1.759 6 5.92 2.90 

Jan. 6 115 1.812 0.517 1.520 0.451 1.559 7 5.96 2.90 

120 1.887 1.868 0.049 0.026 0.498 170 1.464 1.457 0.066 0.046 2.010 0.481 1.663 1.629 0.060 0.037 8 7.17 2.66 

135 1.905 0.472 1.387 0.481 1.663 25 6.24 3.27 

PITTSBURG & MIDWAY MINE, MSHA DISTRICT 11 

Jan. 25 115 2.129 0.745 1.816 0.699 2.005 1 7.10 3.21 

120 2.147 2.228 0.156 0.070 0.735 205 1.792 1.774 0.054 0.030 2.448 0.692 1.985 2.023 0.050 0.025 2 6.93 3.23 

127 2.407 0.703 1.714 0.725 2.079 3 6.03 3.18 

Jan. 26 115 0.609 0.267 0.474 0.256 0.535 4 10.09 3.87 

120 0.599 0.626 0.038 0.061 0.264 281 0.469 0.461 0.019 0.042 0.636 0.262 0.548 0.546 0.011 0.019 5 9.21 3.23 

127 0.670 0.247 0.439 0.266 0.556 6 9.15 3.47 

Jan. 27 115 1.732 0.761 1.435 0.700 1.553 7 6.67 3.29 

120 1.794 1.760 0.031 0.018 0.771 265 1.454 1.418 0.047 0.033 1.957 0.700 1.553 1.558 0.009 0.006 8 6.21 3.48 

127 1.754 0.724 1.365 0.707 1.569 25 6.08 3.32 

EMERALD MINE, MSHA DISTRICT 2 

Feb. 8 115 0.750 0.156 0.630 0.138 0.656 16 8.19 2.61 

120 FL 0.827 0.109 0.132 0.142 124 0.574 0.594 0.031 0.053 0.820 0.141 0.670 0.685 0.038 0.055 17 10.89 2.82 

127 0.904 0.143 0.578 0.153 0.727 18 10.68 2.44 

Feb. 9 115 2.310 0.735 1.802 0.681 1.965 19 7.23 2.68 

120 2.300 2.373 0.118 0.050 0.749 204 1.837 1.779 0.073 0.041 2.454 0.708 2.042 2.017 0.045 0.022 20 7.25 2.89 

127 2.510 0.692 1.697 0.708 2.042 21 6.91 2.78 

Feb. 10 115 0.660 0.213 0.539 0.204 0.607 22 11.44 3.20 

120 NF 0.710 0.071 0.100 0.217 198 0.549 0.529 0.027 0.051 0.729 0.213 0.634 0.631 0.022 0.036 23 13.15 3.16 

127 0.760 0.197 0.498 0.219 0.652 24 11.60 3.34 

FREEDOM MINE, MSHA DISTRICT 10 

Mar. 1 115 1.839 0.518 1.727 0.461 1.808 7 7.33 3.08 

124 1.879 1.861 0.020 0.011 0.486 150 1.620 1.659 0.059 0.036 2.289 0.476 1.867 1.841 0.030 0.016 8 9.02 3.62 

127 1.865 0.489 1.630 0.471 1.847 9 6.82 3.08 

Mar. 2 115 1.255 0.554 1.045 0.269 0.597 10 5.44 2.84 

124 1.322 1.308 0.048 0.036 0.559 265 1.055 1.045 0.010 0.010 1.442 0.545 1.210 0.995 0.345 0.347 11 5.75 2.87 

127 1.347 0.548 1.034 0.531 1.179 12 5.40 2.97 

Mar. 3 115 1.749 0.768 1.542 0.708 1.673 13 5.56 3.29 

124 1.770 1.800 0.072 0.040 0.768 249 1.542 1.524 0.031 0.021 2.103 0.735 1.736 1.693 0.038 0.022 14 6.02 3.26 

127 1.882 0.741 1.488 0.707 1.670 15 5.35 3.20 

PF 

FL 

 Pump failure. 

 PDM file data was a constant value. 

NF Filter not installed. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


 

PDM Dorr-Oliver 2 L/min MRE Dorr-Oliver 1.7 L/min Size distributions 

Date PDM 

No. 

Conc. 

mg/m3 

Avg. 

mg/m3 

Std. 

mg/m3 RSD Mass, 

mg 

Time, 

min 

Conc. 

mg/m3 

Avg. 

mg/m3 

Std. 

mg/m3 RSD 

equiv. 

conc. 

mg/m3 

Mass, 

mg 

Conc. 

mg/m3 

Avg. 

mg/m3 

Std. 

mg/m3 RSD Inst. 

No. MMAD GSD 

JOHN'S CREEK MINE, MSHA DISTRICT 6 

Mar. 15 115 2.550 1.094 2.223 1.037 2.479 1 6.52 2.90 

124 

127 

2.704 

2.796 

2.683 0.124 0.046 1.040 

1.058 

246 2.113 

2.150 

2.162 0.056 0.026 2.983 0.988 

1.043 

2.362 

2.493 

2.445 0.072 0.030 2 

3 

6.27 

6.93 

3.01 

2.95 

Mar. 16 

Mar. 17 

115 

124 

127 

115 

124 

127 

3.955 

4.181 

2.347 

4.400 

4.534 

4.960 

3.494 

4.631 

1.000 

0.292 

0.286 

0.063 

0.874 

0.812 

0.859 

1.072 

0.982 

1.002 

121 

127 

3.610 

3.354 

3.548 

4.219 

3.865 

3.944 

3.504 

4.009 

0.134 

0.186 

0.038 

0.046 

4.836 

5.533 

0.815 

0.784 

0.782 

0.953 

0.967 

0.980 

3.960 

3.810 

3.800 

4.413 

4.477 

4.538 

3.857 

4.476 

0.090 

0.063 

0.023 

0.014 

4 

5 

6 

7 

8 

9 

5.14 

5.94 

6.37 

7.44 

9.85 

8.86 

3.74 

3.56 

3.46 

3.02 

3.46 

3.17 

FORK RIDGE MINE, MSHA DISTRICT 5 

Mar. 29 124 12.149 

127 13.241 12.370 0.785 0.063 

1.128 

1.141 60 

9.400 

9.508 9.578 0.221 0.023 13.217 

1.171 

1.125 

11.480 

11.029 11.261 0.226 0.020 

1 

18 

5.80 

5.66 

2.86 

2.67 

130 11.719 1.179 9.825 1.150 11.275 19 5.89 2.97 

Mar. 30 124 3.633 0.810 3.045 0.759 3.357 20 4.12 2.66 

127 3.741 3.668 0.064 0.017 0.595 133 2.237 2.774 0.466 0.168 3.829 0.761 3.366 3.351 0.018 0.005 21 4.24 2.80 

130 3.629 0.809 3.041 0.753 3.330 22 4.19 2.95 

Mar. 31 124 2.165 

127 2.287 2.184 0.094 0.043 

0.753 

0.804 228 

1.651 

1.763 1.722 0.062 0.036 2.377 

0.703 

0.632 

1.814 

1.631 1.786 0.144 0.081 

23 

24 

4.03 

4.40 

3.03 

3.15 

130 2.101 0.799 1.752 0.742 1.914 25 3.97 2.68 

AIR QUALITY MINE, MSHA DISTRICT 8 

Apr. 19 111 3.332 1.312 3.066 1.164 3.200 1 4.04 4.86 

114 3.188 3.241 0.079 0.024 1.246 214 2.912 3.012 0.087 0.029 4.157 1.149 3.159 3.179 0.021 0.006 2 3.71 4.63 

126 3.203 1.309 3.059 1.156 3.178 3 3.52 4.75 

Apr. 20 111 4.549 1.114 4.253 0.949 4.263 4 3.89 3.90 

114 

126 

4.492 

4.443 

4.495 0.053 0.012 1.100 

1.094 

131 4.200 

4.177 

4.210 0.039 0.009 5.810 0.991 

0.916 

4.451 

4.115 

4.276 0.169 0.039 5 

6 

4.14 

3.56 

3.70 

3.49 

Apr. 21 111 6.881 1.274 6.372 1.075 6.325 7 4.55 3.52 

114 6.779 6.748 0.151 0.022 1.218 100 6.092 6.095 0.275 0.045 8.411 1.124 6.614 6.525 0.174 0.027 8 3.95 3.46 

126 6.584 1.164 5.822 1.128 6.637 9 3.90 3.63 

PANTHER MINE, MSHA DISTRICT 7 

May 17 111 

114 

126 

4.269 

4.218 

4.334 

4.274 0.058 0.014 

1.122 

1.151 

1.184 

169 

3.320 

3.405 

3.503 

3.409 0.092 0.027 4.705 

1.138 

1.129 

1.102 

3.961 

3.930 

3.836 

3.909 0.065 0.017 

7 

8 

9 

4.32 

4.36 

2.47 

2.86 

May 18 

May 19 

111 

114 

126 

111 

114 

6.529 

6.342 

6.405 

2.594 

2.566 

6.425 

2.565 

0.095 

0.029 

0.015 

0.011 

1.399 

1.437 

1.500 

0.741 

0.719 

139 

181 

5.032 

5.169 

5.396 

2.047 

1.986 

5.199 

2.044 

0.184 

0.057 

0.035 

0.028 

7.175 

2.821 

1.437 

1.344 

1.375 

0.709 

0.699 

6.081 

5.688 

5.819 

2.304 

2.272 

5.863 

2.277 

0.200 

0.025 

0.034 

0.011 

10 

11 

12 

13 

14 

4.35 

4.27 

4.52 

5.91 

2.89 

2.91 

2.29 

3.02 

126 2.536 0.760 2.099 0.694 2.255 15 6.25 2.38 

45
 
 

 

APPENDIX C.—ANALYSIS OF VOIDED RESPIRABLE COAL MINE DUST SAMPLES
 

COLLECTED, 1995–2004 

The causes for void samples in the table below include factors in addition to mechanical faults of 

the samplers. Samples collected by both inspectors and coal mine operators are listed. Use of 

the PDM may significantly reduce the number of samples voided for a number of different 

causes. The types of causes amenable to prevention by the PDM are those that relate to 

documentation, timing, and, in some cases, sample weight issues. The PDM generates a unique 

data file for each sample that includes the date, time, and various instrument operating 

parameters, eliminating many documentation issues. The PDM is also programmable to start 

and stop at specific times, avoiding excess sample times. In addition, the PDM provides EOS 

mass and concentration values, eliminating shipping, holding, and some laboratory issues. 

Causes that are considered amenable to reduction by the PDM are indicated by a footnote in the 

table below. Note that certain codes apply only to either inspector or operator samples. 

Inspector Operator 

samples samples 

Total samples collected................................................................... 381,335 487,713 

Nonvoided samples......................................................................... 357,936 (93.9%) 430,710 (88.3%) 

Voided samples............................................................................... 23,399 (6.1%) 57,003 (11.7%) 

BREAKDOWN OF VOIDED SAMPLES 

Abnormal tamper-resistant .............................................................. NA 14 

Abnormal white center..................................................................... NA 6 

Broken1 ........................................................................................... 

Cassette did not match card1 .......................................................... 

204 

63 

1,452 

897 

Cassette not received1 .................................................................... 2 45 

Contaminated1 

................................................................................. 

Dated before notice1 

........................................................................ 

1,166 

NA 

3,023 

1,459 

Designated area not in producing status ......................................... 3 2,123 

Designated work position not in producing status ........................... 

Discarded sample (too old)1 ............................................................ 

Dust data card not received1 ........................................................... 

2 

NA 

3 

919 

2,487 

5 

Excess sample1 

............................................................................... 1 17,431 

Inspector void; rain.......................................................................... 264 NA 

Insufficient dust observed................................................................ 189 867 

Insufficient weight gain.................................................................... 27 3,966 

Invalid certification number.............................................................. 76 610 

Invalid initial weight1 ........................................................................ 108 320 

Invalid occupation code................................................................... 

Invalid or missing date1 ................................................................... 

Invalid or missing time1 ................................................................... 

4 

2 

5,407 

NA 

2 

4,477 

Invalid Part 90 miner ident............................................................... NA 1 

Invalid production ............................................................................ 11,359 9,923 

Invalid sample type.......................................................................... 547 1,410 

Invalid work position........................................................................ 21 1 

Invalid work shift.............................................................................. 

Malfunctioning pump1 

...................................................................... 

2,473 

1,115 

20 

15 

Mine not in producing status ........................................................... 2 NA 

Mining machine unit not in producing status ................................... NA 1,101 

Nonapproved equipment ................................................................. NA 5 

Occupation code–meth mining mismatch........................................ 4 NA 

Operator void; equipment................................................................ 10 2,083 

NA Not applicable. 

1

Amenable to prevention by the PDM. 

46
 
BREAKDOWN OF VOIDED SAMPLES—Continued 

Operator void; location .................................................................... 2 

Operator void; miscellaneous.......................................................... 36 

Operator void; production................................................................ 30 

Operator void; rain........................................................................... 6 

Operator void; time.......................................................................... 13 1 Oversize particles .......................................................................... 263 

Part 90 miner not available.............................................................. NA 

Predated1 ........................................................................................ 4 

492
 

116
 

470
 

15
 

385
 

390
 

8
 

88
 

Quartz laboratory void..................................................................... 7 

Sample not voided........................................................................... 357,936 

Sample received while in hold1

........................................................ NA 

Unacceptable timeframe1 ................................................................ NA 

Unauthorized work position ............................................................. 6 

 Total ............................................................................................ 381,355 

45
 

430,710 

191
 

4
 

137
 

487,713
 

Voided samples potentially prevented by PDM ............................... 8,338 

Percent of voided samples potentially prevented by PDM .............. 35.6 

32,286 

56.6 

NA Not applicable. 1

Amenable to prevention by the PDM. 

Source: MSHA [2005]. 

47
 
Delivering on the Nation’s Promise: 

Safety and health at work for all people 

through research and prevention 

For information about occupational safety and health topics contact NIOSH at:

1–800–35–N IOSH (1–800–356–4674)

Fax: 513–533–8573

E-mail: pubstaft@ cdc.gov

www.cdc.gov/niosh

S AFE R • H E ALT H IE R • P E OP L ET M

DHHS (NIOSH) Publication No. 2006–145