A COMPARATIVE EVALUATION OF THE DIFFERENTIAL-PRESSURE-BASED 

RESPIRABLE DUST DOSIMETER WITH THE PERSONAL GRAVIMETRIC 

RESPIRABLE DUST SAMPLER IN UNDERGROUND COAL MINES 

R.V. Ramani 

The Pennsylvania State University

J.M. Mutmansky 

Honglin He 

The Pennsylvania State University 

J.C. Volkwein 

National Institute for Occupational Safety and 

Health 

V.A. Marple 

B. A. Olson 

P.C. Luna 

University of Minnesota

ABSTRACT 

The development of a sampling instrument for the assessment of an underground coal miner’s exposure to airborne respirable 

coal mine dust on a continuous and real-time basis has been long identified as essential for timely initiation of control actions. 

A respirable dust dosimeter (RDD) which operates on the principle of increasing pressure across a filter media with increasing 

dust mass on the filter has been developed by the National Institute for Occupational Safety and Health. Comparisons of the 

performance of the RDD with an U.S. approved gravimetric respirable dust sampler (GRD) have shown that the RDD may 

meet the requirements for measuring miners’ exposures on a cumulative, near real-time basis such as mid-shift and end of shift 

exposures. Recently, the performances of the RDD and GRD were compared by conducting side-by-side area sampling 

experiments in a controlled experimental environment in the laboratory and in underground coal mines under normal operating 

conditions. In this paper, the results from the in-mine study are presented and discussed. The experimental design for the inmine study included two mines in different coal seams in different geographic coal regions. To ensure a wide range of 

concentrations, the experiments were conducted in a continuous miner section in Mine 1, and a longwall face in Mine 2. 

Airborne dust sampling was conducted for four different shifts at each mine. In each shift, two samples of different exposure 

durations were collected from two different locations. Each sample consisted of the readings of three dosimeters and the 

exposed filters from the three paired GRD samplers. As a result, a total of 96 comparative samples were obtained, 48 for each 

mine. The data were analyzed for the precision of the RDD and GRD measurements and for the relationships between the 

differential pressure of the RDD and the mass of dust on the paired GRD filter. The analyses indicate that, on the average, the 

RDD and the GRD track the airborne respirable dust concentrations well, exhibiting both a high correlation between the two 

measurements and a reliable predictive relationship of one from the other. Details of the experimental design, data analyses 

procedures, results, conclusions and recommendations of the underground experiments are presented in this paper.

KEYWORDS 

Airborne respirable dust, continuous sampling, area sampling; real-time sampling, respirable dust dosimeter, personal 

gravimetric sampler, underground and laboratory experiments 

INTRODUCTION 

Since the enactment of the Coal Mine Health and 

Safety Act of 1969, the assessment of airborne respirable 

dust (ARD) concentrations in U.S. underground coal 

mines has been a subject of much discussion. The issues 

have centered around such topics as personal, 

occupational, and area sampling; continuous versus 

discrete sampling; sampling accuracy; adequacy of 

sampling; and timeliness of results. The need for the 

development of a real-time continuous respirable dust 

monitor, which can provide an assessment of the miner’s 

exposure on a continuous basis, has been apparent for a 

longtime and identified in several recent reports by Mine 
 

 

Safety and Health Administration (MSHA, 1992), 

National Institute for Occupational Safety and Health 

(NIOSH, 1995), and the Secretary of Labor’s Dust 

Advisory Committee (MSHA, 1996). The respirable dust 

dosimeter (RDD) described by Volkwein et al. (1997, 

2000) appears to be a promising development in dust 

exposure measurement. 

The respirable dust dosimeter (RDD) consists of: (1) 

a detector tube which contains a respirable-size 

classifier and a pressure-drop-filter media, [Figure 1], 

and (2) a low-flow pump which pulls the dust-laden air 

through the tube and which has an integral pressure 

transducer with display. As the dust mass loading on the 

filter increases, the pressure drop (i.e. the differential 

pressure) across the filter increases. NIOSH’s 

comparison of the RDD differential pressure increases 

with personal gravimetric mass loadings appear to fit 

well a regression relationship of the type y=axb

, where 

y=differential pressure, x=mass loading, and a and b are 

constants (Volkwein et al., 2000). The fit is better at 

higher mass loadings. 

Recently an independent evaluation of the RDD’s 

performance in comparison to that of the approved 

gravimetric respirable dust sampler (GRD) was 

performed. The evaluation consisted of an assessment 

of the correlation that exists between RDD differential 

pressures and GRD mass loadings when the two types 

of instruments (RDD and GRD) are mounted side by 

side in the laboratory and in mines. Penn State, in 

cooperation with the University of Minnesota 

(UMINN), performed the laboratory and in-mine 

evaluations of the NIOSH-developed respirable dust 

dosimeter (Ramani, 1998). 

The laboratory evaluations were performed at the 

University of Minnesota’s Particle Technology 

Laboratory and the in-mine evaluations at two 

underground coal mines in Pennsylvania. Investigators 

from both Penn State and UMINN were involved in the 

laboratory and in-mine evaluation stages and in the 

interpretation of the results. In this paper the details, 

results and conclusions of the underground experiments 

are presented. 

Figure 1. Respirable Dust Detector Tube 

Figure 2. Photograph showing two gravimetric samplers and one respirable dust dosimeter 
 

EXPERIMENTAL DESIGN 

The underground mine experiments were designed to 

obtain area samples with side-by-side dosimeter and 

gravimetric samplers under a variety of operating 

conditions and dust concentrations. To achieve this 

objective, field tests were performed at two mines in 

two different coal seams. The first mine (Mine A) 

utilized a room-and-pillar system of mining, a singlesplit ventilation system, and a dust scrubber on the 

continuous miner. The second mine (Mine B) used the 

longwall mining system with a shearer for coal 

production. Two sampling locations in each mine were 

chosen so that one was in a position with a high dust 

concentration and the second in a location with a low to 

moderate dust concentration. The locations, while out of 

the path of moving equipment, were in the main flow of 

air through the section. 

The airborne respirable dust concentrations at the two 

locations were sampled for four shifts, each shift lasting 

about six hours. At each location, there were three 

dosimeters and six gravimetric samplers in specially 

designed baskets. Essentially each dosimeter was matched 

with two gravimetric samplers (Figure 2). The sampling 

baskets were hung either on roof bolts or on shields. 

The dosimeters were read several times during the 

shift. However, the most important readings were those 

used in the side-by-side comparisons with the 

gravimetric samplers. The first of these comparison 

readings, taken after approximately three hours of 

sampling, is matched with the mass of dust on the first 

gravimetric sampler to be turned off. The dosimeter and 

gravimetric readings taken at this time are called the 

half-shift readings. The second comparison is made 

after approximately six hours of operation. These 

values are termed the full-shift readings. Essentially, 

one half-shift reading and one full-shift reading were 

associated with each dosimeter used. Each dosimeter 

was used for only one shift during the field experiments. 

This plan results in 48 dosimeter data measurements 

at a mine, each matched with the mass of dust on a 

corresponding gravimetric sampler filter. Further, this 

sampling arrangement allowed the calculation of the 

averages of the three dosimeter readings, and compare it 

to the average of the masses on the three GRD sampler 

filters. There were sixteen pairs of averages for the 

comparative analysis. 

The data obtained from the mines were analyzed for 

ascertaining the association between the dosimeter 

(RDD) pressure increase and the mass of dust on the 

filter of the corresponding personal gravimetric sampler 

(GRD). Specifically, three analyses were performed. 

1) The pressure increase observed in each dosimeter 

was compared with the mass on the filter of the 

corresponding gravimetric sampler. 

2) The average pressure increase observed in a group of 

three dosimeters was compared with the average 

mass on the filters of the three gravimetric samplers. 

3) From the three observations of the RDDs at a station, 

the values for the standard error of the mean (SEM) 

and the relative standard deviation (RSD) were 

calculated. Similarly, from the three observations of 

the GRDs at a station, the values of SEM and RSD 

were calculated. The global averages for SEM and 

RSD were calculated from the individual data. 

For each analysis, the procedures included (i) drawing 

scatter plots of the pairs of data, (ii) fitting least-square 

linear and non-linear equations to the data, and (iii) 

calculating the prediction and confidence intervals for 

the fitted equation. 

Mine A Experiments

Mine A was a room-and-pillar operation in Indiana 

County, PA, located in the Lower Freeport coal seam. 

Two sections were sampled in this study. Both sections 

utilized a Joy continuous miner to mine the coal and a 

Long-Airdox full-dimension mining system to provide 

section coal transport. The full-dimension mining 

system utilized three bridge conveyors and two mobile 

carriers to transfer the coal from the face to the section 

belt conveyor. No pillaring was performed. 

The section layout and the ventilation plan of the first 

section are shown in Figure 3. The intake in this section 

comes up the #1 entry and returns via the #5 entry 

unless it is diverted into the adjacent section. The 

second section sampled used a similar single-split 

ventilation plan except that the air was coursed from 

right to left rather than left to right. Both of the sections 

were planned to have 18,000 cfm (8.5m3

/s) moving 

through the section. The face ventilation was controlled 

by brattice with most of the faces having 3000 to 5000 

cfm (1.4 to 2.4 m3

/s) in the face area. 

The layout shown in Figure 3 indicates the location of 

the intake and return sampling stations. The intake 

baskets were placed in the #3 entry beside the conveyor 

belt. The baskets were located at breathing level near 

the ribline opposite from where the full-dimension 

conveyor system was operating. The dust levels at that 

location were considered to be appropriate for collection 

of small to moderate masses of dust. 

The return sampling station was typically set up 

around one to four breaks downwind of the continuous 

miner location. In this mine, the return sampling station 

was thus about 50 to 200 ft (15 to 60 m) from the 

continuous miner. A typical location is shown in Figure 

3. Note that the return air in the section sampled was 

coursed through an adjacent panel. The continuous 

miner was moving from face to face. Thus, the return 

sampling station was occasionally moved to keep the 

samplers at about the same position relative to the 

continuous miner. The return location was chosen to 

obtain higher masses of dust in the gravimetric samplers 

and dosimeters. Total ventilation in the section was 

measured at 17,300 cfm (8.1 m3

/s) in the crosscut where 

the air was diverted into the next panel and was 

measured at 3000 to 4000 cfm (1.4 to 1.8 m3

/s) in the 
 

 

faces. Measurement was difficult in the face area due to 

a restricted cross-sectional area. 

Figure 3. Typical location of the intake and return 

sampling stations in Mine A 

In the second section, second ventilation went from 

right to left (entry #5 to entry #1) instead of from left to 

right. Face ventilation details were similar to that in the 

first section. The ventilation quantity in this section was 

measured at 18,000/cfm (8.5 m3

/s) in the return. 

Quantities at the face were not measured. 

The production varied from about 460 tons (363 t) to 500 

tons (454 t) for the periods sampled. The sampling in this 

mine proceeded without major problems with the sampling 

instruments. However, a limitation on the duration of 

sampling was imposed by mantrip logistics. As a result, 

the dust loadings were not as high as was desired. 

Experimental Results

The data obtained from Mine A experiments are 

presented in Table 1. In all, 48 sets of comparative data 

were obtained. The examination of all the data after the 

laboratory mass weighing and dosimeter pressure drop 

calculations indicated two consistency problems with 

the collected data. The masses on two gravimetric 

personal samples were inconsistent with the other two 

personal samples at the same locations. The cause was 

not known, but these samples were not utilized in the 

Table 1. Raw Data on Dosimeter Pressure Increase and Sample Mass for Mine A Experiments 

INTAKE RETURN 

 Day Half Shift Full Shift Half Shift Full Shift 

Pres. 

Inc 

Sample 

Mass 

Pres. 

Inc. 

Sample 

Mass 

Pres. 

Inc. 

Sample 

Mass 

Pres. 

Inc. 

Sample 

Mass 

0.4 0.00017 0.4 0.00028 0.5 0.00016 0.7 0.00030 

Mon. 0.5 0.00020 0.7 0.00027 0.6 0.00014 0.9 0.00026 

0.7 0.00016 0.9 0.00028 0.7 0.00013 0.9 0.00029 

0.9 0.00039 0.9** 0.00048 0.7 0.00026 0.9 0.00045 

Tues. 0.9 0.00036 0.9** 0.00049 0.9 0.00030 1.1 0.00049 

1.8 0.00003*** 1.8** 0.00042 1.1 0.00021 1.6 0.00043 

0.9 0.00017 1.1 0.00030 0.9 0.00029 1.1 0.00043 

Wed. 0.4 0.00014* 0.6 0.00006*** 0.9 0.00027 1.2 0.00042 

0.7 0.00025 0.9 0.00030 0.8 0.00030 1.3 0.00046 

.05 0.00007 0.7 0.00011 0.7 0.00022 0.9 0.00021** 

Thur. 0.5 0.00008 0.5 0.00017 0.6 0.00017 1.1 0.00018** 

0.3 0.00009 0.3 0.00010 0.9 0.00026 1.1 0.00005** 

Dosimeter pressure increase (pres. inc.) is in millimeter of mercury (mm Hg) and sample mass in gram (g). 

* This reading is suspect because the hose was found to be disconnected during the experiment. 

** These data are inconsistent as dosimeter pressure readings or gravimetric mass readings did not change from half 

 shift to full shift sampling. 

*** These data are inconsistent with the data read from the other gravimetric samplers in the same group or basket. 
 

analytical procedures. In addition, two groups of fullshift personal samples were nearly identical to the 

matching half-shift samples. As a result of the specific 

problems with these samples they were also excluded 

from further analysis. In summary, only 39 sets of 

comparative data from Mine A were used in the 

subsequent data analyses procedures. 

Results

The scatter plot of 39 pairs of data (side-by-side 

comparison of individual RDD and GRD observations) 

revealed the problem in reading the dosimeter scale in 

mm of mercury (Hg). For small changes in the mass on 

the GRD filter, the scale reading is not sufficiently 

sensitive to show the changing pressure differences. 

This problem is particularly acute in Mine A as the 

amount of the mass on a filter was not only small but 

also within a small range, from 0.05 mg to 0.55 mg. 

Further, at mass loadings less than 0.5 mg, the precision 

of GRD measurements is less (Kogut et. al., 1997) and 

this is reflected in low coefficient of determination of 

the data from this mine. However, the trend for pressure 

difference to increase with increase in the mass is 

evident. The best-fit linear equation is y = 1.9x + 0.30, 

where y = pressure increase in mm of Hg, and x = mass 

in mg and has a coefficient of determination (R2

) of 

0.59. The best-fit non-linear equation is y=1.70 x0.57 

with an R2 value = 0.56. 

The averages of the three dosimeter pressure increases 

and of the corresponding three gravimetric sampler masses 

were calculated for side-by-side comparison of the 

averages. Ideally, for the comparison of the averages, there 

should have been 16 data pairs. Due to the problems 

detected during data collection and analysis stages, only 14 

pairs were available for this purpose. The relative standard 

deviation (RSD), calculated from the 14 gravimetric 

samples, was 0.1 (10 percent). The RSD values from the 

14 dosimeter samples was 0.21. 

A scatter plot of the averages indicates a strong linear 

trend which is confirmed by the linear regression 

equation (y1=2.23x1+0.22) where y1 is the average of 

the three dosimeter pressure increases in mm of Hg and 

x1 is the average of the mass on the filters of the three 

gravimetric samplers in mg. The non-linear regression 

equation fitting the same data is (y1=1.92x1

0.64). The R2 

values for both the equations are about 90%. 

Conclusions

The higher average relative standard deviation (RSD) 

of the dosimeter pressure increases as compared to that 

of the gravimetric mass values indicates the higher 

variability in the dosimeter values. The side-by-side 

comparison of the individual dosimeter and individual 

gravimetric sampler observations resulted in a lower R2

value for the fitted equation as compared to that from 

the comparison of the averages. This is to be expected 

as the averages smooth the individual variabilities. 

However, the lower resolution of the dosimeter pressure 

scale in mm of Hg and the low range of the masses 

collected on the filters may be additionally responsible 

for the low R2

 value in Mine A. Yet, it can be concluded 

that the dosimeter pressure increases as the mass on a 

gravimetric filter increases. 

MINE B EXPERIMENTS 

Mine B was a longwall operation mining coal in the 

Pittsburgh seam in Greene County, PA. The longwall at 

the mine was about 920 ft. (280m) long with 184 shields 

present on the face. The production was accomplished 

with bi-directional cutting by a Joy double-drum 

shearer. The shearer took 42” (1.1m) deep cuts of coal 

ranging from 5 ft. (1.5 m) to 6 ft. (1.8 m) in height. The 

variation in height was due primarily to ability to hold 

the immediate roof of the seam. 

The layout of the longwall panel is shown in Figure 4. 

The two sampling stations were along the longwall face 

with the baskets attached to the shields. The baskets 

were hung on the shield side of the walkway with the 

inlets facing the walkway and in the main flow of 

ventilation air. The intake sampling station was located 

at shield #9. This location was considered to have 

moderate dust loading. The return sampling station was 

positioned at shield #140. The location was selected to 

allow the sampling crew to visit the baskets while the 

shearer was downwind. The dust loadings at this 

location were expected to be very high. The ventilation 

plan for the longwall is also shown in Figure 4. 

The ventilation plan was designed to bring about 

35,000 cfm (16.5 m3

/s) into the section. The intake air 

was measured to be about 28,800 cfm (13.6 m3

/s) at 

shield #9 and at about 11,200 cfm (5.3 m3

/s) at shield 

#140. The loss of air between the two stations is due to 

flow through the gob near the tailgate entries. The 

number of passes of the shearer along the face varied 

from 5 to 10 on the four sampling days. The coal mined 

during the sampling periods varied from about 3000 

tons (2700 t) to about 6000 tons (5400 t) Some 

problems were encountered during the four days of 

sampling at this mine due to which some observations 

from the instruments were lost. 

Figure 4. Location of intake and return sampling station 

in Mine B 
 

Experimental results

The data obtained from Mine B experiments are 

presented in Table 2. As before, 48 sets of comparative 

data were collected. As a result of the problems 

experienced during the experiments which are indicated 

in the table, only 45 sets were useful for subsequent 

analyses. 

The RDD and GRD data from Mine B was subjected 

to the same analysis procedures as the data from Mine 

A. The mass in the gravimetric filters ranged from about 

0.35 mg to 4.5 mg, and the pressure increase in the 

dosimeters, from 0.5 mm of Hg to 20 mm of Hg. As 

with Mine A observations, an increasing trend of 

dosimeter pressure with increasing sample mass is 

evident in Mine B observations as well. 

The scatter plot and the least-square linear regression 

of the gravimetric sample mass versus the dosimeter 

pressure increases for the side-by-side comparison of 

individual observations is shown in Figure 5. The linear 

and non-linear equations and their respective R2

 values 

are y=1.75x + 0.29 (R2

 = 0.90), and y=1.96x0.99 (R2 = 

0.90), where y = dosimeter pressure increase in mm of 

Hg, and x = gravimetric mass in mg. Both equations 

have a high coefficient of determination (R2

=0.90), 

indicating a very good fit. The value of the exponent in 

the non-linear equation is 0.99, indicating that, within 

the range of values, the two variables have a high 

degree of linear association. 

The averages of the three dosimeter pressure 

increases, and the corresponding three gravimetric 

masses were calculated. In the comparison of the 

averages, all 16 data pairs were utilized. In the case of 

samples 8, 15, and 16, only two observations were 

available for the calculation of the averages. The 

average relative standard deviations, calculated from the 

GRD and RDD averages, are 0.10 and 0.21. The scatter 

plot of the GRD mass versus RDD pressure increase, 

and the associated linear equation are shown in Figure 

6. The linear and non-linear least -square regression 

equations are respectively y1=1.76x1+0.28; and 

y1=1.98x1

0.99. As before, y1 and x1 respectively stand for 

the averages of the pressures increases in the three 

dosimeters and the average of the masses on the three 

gravimetric filters at a station. Both equations have R2

values of 95%. Clearly, the average pressure increase 

across the RDD filters is a good predictor of the average 

mass on the GRD filters. Further, the exponent of the 

non-linear equation is close to unity. Therefore the 

relationship is strongly linear in the range of mass 

loadings that was experienced in Mine B. 

Table 2. Raw Data on Dosimeter Pressure Increase and Sample Mass for Mine B Experiments 

Shields 8-9 Shields 140-141 

 Day Half Shift Full Shift Half Shift Full Shift 

Pres. 

Inc 

Sample 

Mass 

Pres. 

Inc. 

Sample 

Mass 

Pres. 

Inc. 

Sample 

Mass 

Pres. 

Inc. 

Sample 

Mass 

0.6 0.00044 1.1 0.00064 3.9 0.00100 5.1 0.00180 

Mon 0.75 0.00045 1.12 0.00066 3.2 0.00121 4.3 0.00207 

0.93 0.00047 1.31 0.00064 2.24 0.00114 3.36 0.00187 

0.9 0.00038 2. 0.00091 3. 0.00141 5.1 0.00357 

Wed 0.9 0.00035 1.1 0.00073 3.1 0.00183 6. 0.01520* 

0.9 0.00043 1.3 0.00085 2.9 0.00148 5.6 0.00354 

0.8 0.00044 1.1 0.00091 5.3 0.00252 7.6 0.00429 

Fri 1.4 0.00049 1.6 0.00093 4.5 0.00255 7.2 0.00448 

1.1 0.00037 1.6 0.00080 5.5 0.00226 8.2 0.00396 

0.5 0.00040 0.7 0.00044 ** 0.00128 ** 0.00192 

Thur 0.9 0.00034 1.2 0.00057 2.2 0.00099 4.2 0.00208 

0.6 0.00035 0.6 0.00053 2.7 0.00091 4.7 0.00193 

Dosimeter pressure increase (pres. inc.) is in millimeter of mercury (mm Hg) and sample mass in gram (g). 

* This reading is suspect because the hose was found to be disconnected during the experiment. 

** In these two cases, the dosimeter pressure readings could not be obtained. 
 

y = 1,749x + 0,2945

R2

 = 0,9037

0,00

1,00

2,00

3,00

4,00

5,00

6,00

7,00

8,00

9,00

0,00 1,00 2,00 3,00 4,00 5,00

Sample Mass (mg)

Pressure Increase (mm Hg)

Figure 5. Scatter Plot of the One to One Sample GRD Mass and RDD Pressure Increase data, and the Associated 

Least Square Linear Regression Equation for Mine B Data 

y = 1,7598x + 0,2836

R2

 = 0,9479

0,00

1,00

2,00

3,00

4,00

5,00

6,00

7,00

8,00

9,00

0,00 1,00 2,00 3,00 4,00 5,00

Sample Mass (mg)

Pressure Increase (mm Hg)

Data for Mine B

No. of Stations/Mine: 2

No. of Samples / Station / Shift: 2

No. of Shifts Sampled:4 

Total No. of Samples:16 

No. of Useful Samples: 16

Figure 6. Scatter Plot of the Averages of the Sample Masses and Pressure Increases, and the Associated 95% 

Error Bars, and the Least Square Linear Regression Equation for Mine B Data 

Conclusions

The results from Mine B confirm that the dosimeter 

(RDD) readings have a higher variability than the 

gravimetric readings. The side-by-side comparison of 

the individual readings from the two instruments 

through regression analysis shows a much higher R2

value (90%) compared to that from the Mine A reading 

(59%). It is likely that, when subjected to a wider 

range of dust loadings, the problem with the low coefficient of correlation between the RDD and GRD is 

decreased. 

The comparison of the averages of the readings of the 

two instruments also confirms the existence of a high 

degree of predictability of the average of the mass 

loadings on gravimetric filters from the average of the 

pressure increases in corresponding dosimeters. The 

linear and non-linear relationship derived from Mine B 

readings also have high R2

 values (95%), as compared 

to those (R2

=90%) from Mine A readings. 

The comparison of the side-by-side, one-to-one 

measurements, and that of the averages of the 

combined data set of Mine A and Mine B data reveal 

that the predictive linear relationship between the RDD 

and the GRD data is quite strong. The value of the 

coefficient of variation (R2

) for the regression equation 

is 93%, which is higher than those for Mine B (90%) 

and Mine A (56%). Caution must be exercised in 

extrapolation of this finding to different coals. Firstly, 

the amount and the range of mass loadings in Mine A 

were rather small (0.05 mg to 0.55 mg) as compared to 

that for Mine B (0.35 mg to 4.50 mg). Secondly, the inmine variations in Mine A may be higher on the factors 

that influence the RDD and GRD performances than the 

mine-to-mine variations between Mine A and Mine B. 

The controlled experiments in the laboratory may 

provide more reliable information on the impact of 

different coal dusts on the RDD and GRD 

performances. 
 

Table 3. Ranges of the Relative Standard Deviations of the Personal Gravimetric Sampler (GRD) and the Respirable 

Dust Dosimeter (RDD) from Mine A, Mine B and Mine A andMine B Combined Data. 

 Instrument Mine A Data Mine B Data Mine A and Mine B Data

 Min Max Average Min Max Average Min Max Average

Personal Gravimetric 

Sampler, (GRD) 0.021 0.299 0.100 0.006 0.184

 

0.006 0.299 0.100 

Respirable Dust 

Dosimeter (RDD) 0.0670 0.433 0.214 0.033 0.386 0.214 0.033 0.433 0.214 

Table 4. List of the Linear and Non-linear Equations from Mine A and Mine B Data 

 Data From Analysis Number of 

 Data Pairs Linear Equation Non-Linear Equation 

One-to-One 39 y=1.90x +0.30 R2=0.59 y1=1.70x0.57 R2 Mine A =0.57 

Average 14 y1= 2.23x1+0.22 R2

=0.91 y1=1.92x1

0.64 R2

=0.89

One-to-One 45 y =1.75x+0.29 R2=0.90 y=1.96x0.99 R2 Mine B =0.90

Average 16 y1=1.76x1+0.28 R2

=0.95 y1=1.98x1

0.99 R2

=0.95

One-to-One 84 y=1.74x+0.33 R2=0.93 y=2.09x0.76 R2 Mine A and =0.86

Mine B Average 30 y1=1.74x1+0.32 R2

=0.96 y1=2.14x1

0.77 R2

=0.93

SUMMARY 

In underground mine experiments, the performance of 

a total of 96 respirable dust dosimeters (RDD) was 

evaluated by comparing the pressure increase across 

each dosimeter filter to the mass of dust collected on the 

filter of a matching personal gravimetric sampler 

(GRD). The dosimeters were equally split between two 

mines, Mine A and Mine B. The samplers were 

exposed to additional temporal and spatial variability of 

airborne dust concentrations as sampling was conducted 

at each mine for four different days at two distinct 

locations with at least six hours of sampling per day. At 

each location, there were three dosimeters and six 

gravimetric samplers. 

Some of the limitations of the data must be recognized. 

The data for the study came from only two mines. 

Further, the dust loadings in Mine A were rather small, 

and varied only over a small range. Even with the most 

careful experimental design and execution, some data 

collected during the experiments were found to be 

questionable. However, sufficient data were available for 

the analyses needed by the study. Therefore, the 

conclusions drawn from these analyses are valid. 

From the three RDD and GRD readings at a location, 

the coefficients of variation [or the relative standard 

deviation (RSD)] of the RDD and GRD were calculated. 

The range of the individual RSD values calculated from 

the Mine A, Mine B, and the combined Mine A and 

Mine B data are shown in Table 3. The RSDs for both 

the GRD and the RDD vary over a wide range. The 

average of the calculated RSDs for GRD is 0.0999 

(nearly 10%), and that for the RDD is 0.2136 (over 

21%). Clearly, on the average, a respirable dust 

dosimeter reading is associated with greater uncertainty. 

The linear and non-linear regression equations and 

associated coefficients of determination (R2

) of the sideby-side, one-to-one, comparison of the RDD (y) and 

GRD (x) readings as well as of the average RDD (y1) 

and GRD (x1) readings obtained from Mine A, Mine B, 

and combined Mine A and Mine B data are shown in 

Table 4. As already indicated, the data from Mine A 

encompassed not only very small mass loading but also 

a very narrow range of mass loadings. Even then, the 

linear equation based on the averages has a R2

 of 91%, 

indicating that a very high degree of linear association 

between the GRD and RDD averages. The 

representation of the relationship between the GRD and 

RDD by a linear equation appears to be appropriate 

since the values of R2

 for the non-linear relationship are 

loweror at most equal, and in several cases, the 

exponent values are close to unity. On the basis of this 

experimental study, it is concluded that the pressure 

increase across the respirable dust dosimeter filter is 

strongly related to the mass of dust on the 

corresponding personal gravimetric sampler 

filter.Further, it is concluded that this relationship is 

strongly linear in the range of mass loadings 

experienced in the two mines. Therefore, the dosimeter 

reading is a good surrogate of the mass of dust on a 

personal gravimetric filter, and can be used to 

approximate the cumulative dust exposure, calculated 

either as a mass or a time-weighted concentration. The 

development of an appropriate calibration curve for use 

in the field with the dosimeters must take into account 

the several influencing factors discussed here.Controlled 
 

experiments in the laboratory should provide additional 

insights to this challenging but very rewarding task. 

ACKNOWLEDGEMENTS 

The financial support from the National Institute for 

Occupational Safety and Health, and the co-operation 

from the mining companies are gratefully appreciated 

and acknowledged. 

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