Benchmarking longwall 


dust control technology and practices
 

by James P. Rider and Jay F. Colinet 

Abstract n Significant advances in longwall mining technology and equipment have occurred

over the last decade. By the late 1990s, longwall mine output accounted for 40% of all

underground output in the U.S. and today longwall mines account for approximately 50% of

coal produced underground in the United States. A 51% increase in average shift production

rates has occurred over the last 15 years. This increased longwall productivity has meant that

far more dust is being produced and controlling respirable coal dust presents an ongoing

challenge for coal mine operators. The National Institute for Occupational Safety and Health

(NIOSH) conducted a series of benchmark surveys at longwall operations across the country

to identify current operating practices and the types of controls being used. Gravimetric and

instantaneous dust sampling was completed to quantify the dust levels generated by major

sources on the longwall section and to identify different control technologies in use today.

Substantial reductions in dust levels were realized at sampling locations on the face when

compared with ongwall surveys conducted in the 1990s. Results from the underground dust

surveys and current longwall dust control technology and operating practices will be discussed.

Introduction 

The longwall mining industry has 

seen remarkable and significant improvements in longwall mining equipment and mining practices since the 

mid-1990s. Average shift production 

has increased from 3,266 t (3,600 st) per 

shift in 1994 to approximately 4,990 t 

(5,500 st) per shift in 2008. A dramatic 

decrease in working faces from 80 to 

46 has occurred over the same time 

period. Today, the average face width 

has increased to 318 m (1,043 ft), with 

one longwall operation reporting a face 

width of 549 m (1,800 ft) compared to 

an average of 229 m (750 ft) in 1994 

(Fiscor, 2009). Panel lengths in 2008 averaged 3,276 m (10,749 ft) compared 

to 2,134 m (7,000 ft) in 1994. Also, the 

average cutting height was 2.7 m (8.5 

ft) with a range between 2.1 and 3.4 m 

(7 and 10 ft).The power made available 

to the shearer has increased dramatically.Today, the average power installed 

on the shearer is 1,185 kW (1,589 hp) 

compared to 940 kW (1,260 hp) just five 

years ago. Overall production from U.S. 

longwall mines peaked in 2004 and decreased by approximately 10 percent in 

2007 with over 160 Mt (176 million st) 

mined (Energy Information Administration, 2008). These production rates 

continue to challenge dust control efforts of the industry. 

Longwall personnel can be exposed 

to harmful respirable dust from multiple dust generation sources including: 

intake entry, belt entry, stageloader/ 

crusher, shearer and shield advance. 

For a five-year period ending in 2008, 

valid compliance sampling for longwall 

designated occupations or high-risk occupations, taken by mine operators and 

U.S. Mine Safety and Health Administration (MSHA) inspectors, indicated 

that 11% of the samples exceeded 2.1 

mg/m3 (Niewiadomski, 2009). In addition, MSHA inspector sampling results 

for the same five-year period showed 

that longwall face workers were exposed to elevated levels of respirable 

silica dust. For MSHA occupation 

codes 044 (tail-side shearer operator) 

and 041 (jack-setter), which are subject 

to reduced dust standards due to silica 

levels, 31% and 21% of the samples, respectively, exceeded the reduced standard (MSHA, 2009). 

NIOSH initiated a surveillance program to quantify the levels of dust being generated by major sources found 

on today’s longwalls, identify the types 

of controls in use and quantify the levels of application for these control technologies. Survey results were compared 

to results from a U.S. Bureau of Mines 

(USBM) study conducted in the 1990s 

(Colinet et al., 1997). 

Sampling methodology 

Gravimetric dust samplers, identical 

to those used in compliance sampling, 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

were operated at 2 L/min (0.071 cu ft/min) in conjunction 

with 10-mm (0.04-in.) Dorr-Oliver nylon cyclones. Samplers 

were utilized at stationary and mobile sampling locations to 

quantify the levels of respirable dust generated at prominent 

sources along the longwall face. Gravimetric sampling was 

conducted for four to six hours and calculated concentrations 

were not converted to mining research establishment (MRE) 

equivalent dust levels and should not be compared to compliance sampling concentrations. 

Personal DataRAMS (pDRs) were used adjacent to the 

gravimetric samplers at select sampling locations to obtain a 

time-related profile of dust levels generated during each sampling period. The pDR is an MSHA-approved, instantaneous 

dust measuring device in which dust-laden air passes through 

a sampling chamber and a light source. The amount of light 

deflection in the chamber is measured and provides a relative 

measure of the dust concentration. Instantaneous dust levels 

were stored at 10-second intervals in an internal data logger 

and then downloaded onto a computer for analysis. Dust 

levels measured with the pDR can be calculated for any time 

period of interest (e.g., head-to-tail or tail-to-head passes). 

Mobile dust sampling to determine the amount of dust 

generated by the shearer and by movement of advancing 

shields was conducted by a three- or four-member NIOSH 

sampling team. Ideally, the upwind sampling location was 

approximately 4.6-7.6 m (15-25 ft) upwind of the headgate 

cutting drum and measured intake dust levels reaching the 

shearer. The shearer sampling location was located between 

mid-shearer and upwind of the tailgate drum. This sampling 

crew member tried to position himself within a shield or 

two of the tailgate shearer operator. Sampling data from 

this location provided an indication of the amount of dust 

generated by the headgate drum that migrated into the walkway. If permitted, the downwind sampling location was approximately 4.6-7.6 m (15-25 ft) downwind of the tailgate 

drum. Each team member maintained their relative position 

with the shearer as it moved across the face. Differences 

in dust levels between the upwind and downwind sampling 

locations can be attributed to dust generated by the shearer. 

Also, whenever possible, sampling was conducted upwind 

and downwind of shield movement on head-to-tail passes to 

determine dust liberated during shield advance. 

At each mobile sampling location, sampling crew members wore a specially designed sampling vest that contained 

two permissible sampling pumps and four cyclone sampling 

units with appropriate filter cassettes, along with tygon tubing 

used to connect the sampling units to the pumps. The respirable dust fraction was deposited onto preweighed 37-mm 

(0.15-in.) PVC filters. All filters were pre- and post-weighed 

in an environmentally controlled NIOSH laboratory in Pittsburgh and respirable dust concentrations were calculated. 

The sampling units were fastened to the upper chest area 

near the shoulders, two units on the left side of the chest 

area and two units on the right side. One sampling unit on 

the right and left side of the chest area were connected to 

the permissible pumps and used to sample dust levels during 

head-to-tail passes. When the shearer reached the tailgate 

area, the tubing from these sampling units was disconnected 

from the pumps and tubing from the other two sampling 

units was connected to the pumps and used to monitor dust 

levels for tail-to-head passes. If the shearer was stopped for 

an extended period (approximately greater than 3 minutes), 

the gravimetric pumps were paused, so that mobile sampling 

along the face was representative of dust levels during active mining. Along with the gravimetric sampling package, 

members of the sampling crew carried a pDR sampler. Gravimetric concentrations were compared to the associated pDR 

data and correction factors were calculated by dividing the 

concentrations from the gravimetric samplers by the pDR 

average concentration. The correction factors were then 

applied to the instantaneous readings from the pDRs, as 

recommended by the pDR manufacturer. 

Mobile sampling was augmented with stationary sampling packages. At each stationary sampling location, two 

gravimetric samplers were located adjacent to one another 

and operated over the same sampling period. Stationary 

sampling locations included the intake, belt entry, shield 10, 

and approximately 10 shields from the tailgate. Intake samplers were typically located in the last open crosscut and 

used to isolate the dust contamination from sources outby 

the longwall face. If the mine was using the belt entry for 

additional intake air, gravimetric samplers were located in 

the belt entry at least 15.2 m (50 ft) outby the stageloadercrusher unit. Shield 10 samplers were hung in the walkway 

close to the shield legs and used to monitor the respirable 

dust moving onto the face. The difference between dust levels measured at shield 10 and outby sources (intake and belt) 

represent an estimate of dust liberated by the stageloader/ 

crusher dust source. The tailgate sampling package provided 

an indication of the total dust generated along the face. The 

sampling units were typically started after arrival upon the 

longwall face and operated continuously until sampling was 

completed. 

In addition to dust measurements, sampling personnel 

monitored airflow quantities on the longwall section. During 

each shift of sampling, spot air velocity readings were taken 

with handheld anemometers at 10-shield intervals down the 

face. These measurements were one-minute readings taken 

approximately 0.3 m (1 ft) above the spill plate of the face 

conveyor. Also, an estimate of the area at each velocity sampling location was calculated to estimate the air quantity 

present. If possible, water flow meters were installed in the 

water line supplying the shearer and the line supplying the 

stageloader/crusher sprays. Periodic readings were taken 

from each of these meters to monitor the quantity of water 

being used to suppress dust. 

Longwall conditions and controls 

Approximately 25% of the active longwall faces in the 

U.S. were surveyed to quantify dust generation from major 

sources and determine the relative effectiveness of the different control technologies. Respirable dust surveys were 

completed at longwall mining operations located in Alabama, 

Colorado, New Mexico, Pennsylvania and West Virginia to 

collect data representative of mining conditions found in 

the mining regions across the country. Five longwalls were 

located in the eastern United States and five longwalls were 

surveyed in western states. Seven of the mines utilized a bidirectional cutting sequence and three were taking unidirectional cuts. Mining heights ranged between 2.3-3.7 m(7.5-12 

ft), while face widths varied between 229 and 305 m( 750 and 

1,000 ft). 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Velocity readings were recorded approximately every 

10 shields along the longwall face. Face velocities are seldom uniform and may not be representative of average face 

velocities but, with a ventilation profile, the mine operator 

may discover problem areas and more accurately assess the 

ventilation parameters on the face. Average face velocities 

increased by 28% (0.71 m/sec or 140 ft/min) when compared 

to air velocities reported in the mid 1990s longwall study 

(Colinet et al., 1997). The average velocity of the surveyed 

longwalls was 3.4 m/sec (637 ft/min). Eight of the longwalls 

had average air velocities greater than 3.0 m/sec (600 ft/min) 

and two mines averaged over 4.1 m/sec (800 ft/min).Average 

air quantities increased approximately 51% when compared 

to the mid-1990 longwall study. The average volume along 

the face was approximately 30.7 m3/sec (65,100 cu ft/min), 

with a range between 24.3 to 39.1 m3/sec (51,600 to 83,000 cu 

ft/min). Air quantity observed for seven of the longwalls was 

greater than 30.2 m3/sec (64,000 cu ft/min). 

Along with an escalation of air down the face, the use of 

water to the shearer has also increased in an effort to control 

dust liberated from the face. An average of 492 L/min (17.3 

cu ft/min) of water volume was observed at the shearer. The 

number of shearer drum sprays ranged between 35 and 62, 

and the average drum spray pressure was approximately 

1,034 kPa (150 psi). Half of the mines surveyed utilized crescent sprays on the ranging arms, with the number of sprays 

ranging between 7 and 10. 

Headgate splitter arm directional spray systems were 

observed on 90% of the surveyed longwalls. The exact type, 

number and location of these sprays varied significantly between mines, but all were operating on the principle of splitting the ventilating air as it reaches the headgate side of the 

shearer and holding the dust-laden air near the face. The 

length of the splitter arms varied between 2.7 m (9 ft), and 4.6 

m (14 ft), while the number of sprays ranged between 6 and 

19. Thirty percent of the surveyed longwalls utilized venturi 

sprays, which were mounted on top of the splitter arm and 

operated with spray pressures in excess of 1,551 kPa (225 

psi). Average spray pressures were approximately 690 kPa 

(100 psi) when hollow cone sprays were used. Sprays were 

directed downwind and oriented in the direction of the roof, 

toward the face or face conveyor. Extension arms attached 

to the end of splitter arms were observed on three longwall 

faces.The lengths of the extension arms ranged between 45.7 

to 61.0 cm (18 to 24 in.) and were angled between 30 and 45 

degrees toward the face. 

Water spray manifolds positioned between the drums 

or sprays located on deflector plates spanning the length of 

the shearer were observed on all longwall surveys. Various 

types of spray manifolds were observed at the eastern longwall sites. Three or four manifolds consisting of four or five 

sprays were evenly spaced across the length of the shearer. 

The manifolds were either located on the face side of the 

shearer or on the top of the shearer close to the face. At one 

longwall operation, spray manifolds were located toward the 

middle of the shearer and elevated 15.2 to 30.5 cm (6 to 12 

in.) above the shearer body. Sprays were oriented downwind 

toward the face, roof or floor. Deflector or sloughing plates 

were observed at 80% of the western longwalls. The primary 

function of the shearer deflector plates is to protect shearer 

operators from debris flying off the face. 

However, in a raised position, the deflector plates seem to 

enhance the directional spray system effectiveness by providing a physical barrier that helps to confine contaminated air 

close to the face. Deflector plates were either a single plate 

that covered the length of the shearer or were split into three 

independent sections that spanned the length of the shearer. 

All deflector plates were equipped with sprays located near 

the center or top of the plate and evenly spaced across the 

length of the plate.The type of sprays were mine-specific and 

were either venturi or hollow cone sprays. 

Manifolds located above the lump breaker or on the 

shearer body to control dust in the tailgate drum area were 

observed on all but two longwalls. A minimum of four and 

maximum of 16 sprays were directed toward the cutting drum 

or down onto the conveyor.The use of the tailgate-side splitter arm has declined when compared to the 1990s longwall 

surveys (Colinet et al., 1997). Tailgate-side splitter arms were 

observed on 20% of the surveyed longwalls. An alternative 

to the tailgate-side splitter arm is a spray manifold on the tailgate end of the shearer that was seen on two surveys. These 

sprays were oriented parallel to the tailgate ranging arm or 

angled slightly toward the tailgate drum and act as a water 

curtain confining the dust cloud near the face. These sprays 

carried water a distance of 4.6 to 7.6 m (15 to 25 ft) downwind 

of the shearer and seemed to enhance the air split created by 

the shearer’s directional spray system. 

Shield sprays were mounted on the underside of the 

shields on one-fifth of the longwalls. These sprays were automatically activated by the shearer with the intent to create 

a moving water curtain to contain the dust cloud near the 

headgate and tailgate drum areas. Each shield was equipped 

with one or two rows of two sprays located near the tip of the 

shield.The sequencing of when the sprays were activated and 

deactivated was mine-specific. Proper sequencing of shield 

sprays is critical for these sprays or a negative impact on controlling dust level may occur as observed during the surveys. 

Shield sprays interacted with the upwind splitter arm sprays, 

creating turbulence that resulted in a dust and mist cloud 

rolling into the walkway. 

Longwall dust concentrations 

Table 1 summarizes gravimetric dust concentrations from 

both the stationary and mobile sampling locations.The minimum, average and maximum dust levels for mobile and stationary sampling locations along with shield dust are shown 

in Fig. 1. Intake dust levels averaged 0.20 mg/m3, with 70% 

of the longwalls below 0.25 mg/m3

. Six of the longwall faces 

utilized belt air to supplement the intake air on the longwall 

face. Dust levels ranged between 0.30 mg/m3 and 0.72 mg/ 

m3. The average dust concentrations from these two outby 

sources researching the stageloader area was 0.23 mg/m3 and 

ranged between 0.03 mg/m3 and 0.44 mg/m3. The dust level 

monitored at shield 10 is a good indication of the dust entering the face from the stageloader/crusher along with outby 

sources from the intake and belt.Average dust concentration 

found at shield 10 was 0.70 mg/m3

. The difference between 

shield 10 dust levels and the outby dust sources is primarily 

dust generated by the stageloader-crusher unit. On average, 

the amount of dust that can be attributed to the stageloader/ 

crusher was 0.47 mg/m3 . 

A good indication of the amount of total dust generated 
 

Table 1 

Summary of average gr

Mine Intake 

A 0.18

B 0.22

C 0.34

D 0.16

E 0.03

F 0.17

G 0.04

H 0.26

I 0.42

J 0.20

avimetric du

Belt 

NA

0.35

0.55

0.42

NA

NA

NA

0.30

0.50

0.72

st concent

Shield 10

0.80

0.78

0.99

0.91

0.26

0.48

0.26

0.86

0.89

0.72

ration for 

 U

H to T 

2.68

4.19

1.33

1.96

0.43

2.96

0.84

1.05

2.42

1.42

stationar

pwind

T to H 

1.50

1.53

1.53

1.87

0.43

0.81

0.38

1.30

1.15

0.80

y and mo

 S

H to T 

2.23

3.36

1.94

2.15

2.27

2.12

0.79

3.09

3.17

1.35

bile samp

hearer

T to H 

1.68

1.42

2.37

2.29

1.59

1.08

0.73

2.29

1.44

1.60

ling loca

 Downwind 

H to T 

4.03

4.91

4.30

3.56

4.26

2.46

NA

3.92

3.56

2.10

T to H 

4.35

1.57

7.23

2.91

6.24

2.98

NA

2.45

1.29

2.51

tions (mg/m3

). 

Tailgate 

2.36

3.88

3.80

2.21

3.16

1.04

2.33

1.72

1.91

2.34

Figure 1 

Range of dust levels measured for stationary and mobile sampling locations. 

along the face was monitored 

at the tailgate sampling location. Dust levels ranged between 1.04 mg/m3 to 3.88 mg/ 

m3 and averaged 2.48 mg/m3. 

Overall dust levels were below 

2.5 mg/m3 for 7 of the 10 longwalls. Shield dust could only 

be isolated on half of the longwall faces, due to either shield 

movement occurring downwind of the shearer or adverse 

roof conditions, where shield 

advances were random and 

unpredictable. Average dust 

generation attributed to shield 

movement was 1.18 mg/m3

. 

Comparing dust levels 

at shield 10 with the upwind 

samples from the tail-to-head 

passes showed an increase of 

0.43 mg/m3 near the shearer. 

Dust liberated by face spalls, 

from the face conveyor and 

dust migrating from the gob 

may be causing the increase 

in dust levels. As air velocities increase, it is important to 

ensure that sufficient wetting 

of the coal is provided to minimize the potential of increased 

entrainment with the higher air 

velocities. 

An assessment of the dust 

levels when shields were advanced outby the shearer com­
 

Table 2 

Comparison of dust levels when shields were advanced upwind of the shearer vs. downwind. 

Shield movement outby shearer (mg/m3

) 

Head-to-tail Tail-to-head 

Upwind Shearer Downwind Upwind Shearer Downwind 

Minimum 0.43 0.79 2.46 0.38 0.73 1.29

Average 2.17 2.40 3.81 1.12 1.57 3.11

Maximum 4.19 3.36 4.91 1.87 2.29 6.24

Shield movement inby shearer (mg/m3

) 

Head-to-tail Tail-to-head 

Upwind Shearer Downwind Upwind Shearer Downwind 

Minimum 1.33 1.35 2.10 0.80 1.60 2.51

Average 1.38 1.65 3.20 1.17 1.99 4.87

Maximum 1.42 1.94 4.30 1.53 2.37 7.23

Figure 2 

Comparison of average dust concentration for stationary sampling locations and shield 

dust from the 1990s and 2000s surveys. 

pared to shields movement inby the shearer is shown in Table 

2. A prominent increase in dust levels occurred at the upwind and shearer sampling locations on head-to-tail cuts 

when shields were advanced outby the shearer. This result 

supports the hypothesis that much of the dust liberated during head-to-tail passes is generated by advancing shields. On 

the recently completed surveys, shields were shearer activated and advanced between two and five shields outby the 

headgate drum. These advancing shields are the only major 

dust generation source between the stageloader-crusher unit 

and the shearer on head-to-tail cuts.A good indication of the 

amount of dust attributed to shield movement is to compare 

head-to-tail upwind samples when shields were activated 

upwind of the shearer with tail-to-head upwind samples.The 

tail-to-head samples include dust generated by face spalling 

and conveyor dust and are a good indicator of dust levels 

outby the advancing shields. Evaluating these upwind sampling locations showed a substantial increase of 1.05 mg/m3 

that may be directly attributed to fugitive dust generated by 

advancing shields. Also, a comparison of head-to-tail upwind 

samples from shield movement outby and inby the shearer 

showed an increase of 0.79 mg/m3. 

The difference in average dust levels between the upwind 

and shearer sampling position isolates the dust generated by 
 

Figure 3
	

Comparison of average dust concentration for mobile sampling locations from the 1990s and 2000s surveys. 

the headgate drum. Increases of 0.32 mg/m3 and 0.52 mg/m3 

occurred for head-to-tail and tail-to-head cuts, respectively. 

During tail-to-head cuts, the headgate drum is the primary 

cutting drum, which resulted in a 0.20 mg/m3 increase in dust 

levels compared to the dust levels from the headgate drum 

on cleaning passes. On tail-to-head passes, the cutting drum is 

exposed directly to the airflow, which may result in increased 

turbulence and the potential to elevate dust levels. Calculating dust levels generated by the shearer is accomplished by 

subtracting the upwind sampling concentrations from the 

downwind concentrations. Average shearer-generated dust 

was found to be 1.75 mg/m3 when mining headgate to tailgate. 

Identifying shearer dust for tail-to-head passes could not 

be performed because of the close proximity of the shield 

movement to tailgate drum. Dust samples locations varied 

between inby and outby advancing shields; consequently, 

shield dust could not be separated out of some of the downwind samples. As expected, downwind dust levels were approximately 1.1 mg/m3 higher than the dust measured at the 

tailgate sampling location. Downwind dust levels represent 

dust generated during mining, while the tailgate samples 

include dust levels for the entire sampling period, including 

downtime. 

Discussion 

Figure 2 compares average dust levels at the stationary 

sampling locations and shield dust with the survey data from 

the 1990s study (Colinet et al., 1997). Reductions in dust 

levels ranged between 20% and 47%.A significant reduction, 

47%, in intake dust levels and reduced dust levels on the face 

may be attributed to a 22% increase in air velocity on the 

face observed in the recently conducted surveys compared 

to 1990s surveys. Past research efforts (Jankowski and Colinet, 2000) have shown that higher velocities provide greater 

quantities of air to the face for better dilution of intake dust, 

as well as dust generated during support movements.A 37% 

reduction in dust levels at the shield 10 sampling location is a 

good indication that the enclosed stageloader-crusher units 

with installed water sprays systems and scrubbers have had 

a positive impact at reducing face workers’ dust exposure 

levels. 

An evaluation of the average dust levels at mobile sampling locations for the surveys conducted in the 1990s and 

the recently completed surveys is shown in Fig. 3. Substantial reductions have occurred at all three sampling locations 

for both cutting directions. A greater-than 22% increase in 

air velocity and air volume on longwall faces in the current 

survey results, along with much improved directional spray 

systems, had a positive effect at reducing face dust levels. 

Upwind dust levels were reduced between 24% and 45%. 

Although a reduction was seen at head-to-tail upwind and 

shearer sampling locations, these dust levels may be influenced by the number of operations performing bidirectional 

cuts, the close proximity to the shearer shield movement is 

occurring and the increase in the number of shields activated 

per shift. Past research (Tomb et al., 1992) has shown that 

higher air velocities provide better dilution of fugitive dust. 

If roof conditions allow, advancing shields as far outby the 

shearer as possible when mining toward the tailgate may allow for better dilution of the shield-generated dust and may 

lower dust levels for the shearer operators. A 58% reduction 

in dust levels can be seen at the shearer sampling location for 

tail-to-head cuts when comparing surveys from 1990 and the 

current surveys. Reductions of 45% and 39% were realized 

at the downwind sampling position, once again confirming 

that an increase in air and much improved directional spray 

systems had a positive effect on lowering longwall face dust 

levels. 

Identifying the contribution level of respirable dust 

sources was accomplished by calculating the difference between dust levels immediately upwind and downwind of the 

known source. As in previous surveys, dust contributions 

from the shearer, shield movement, intake and stageloadercrusher were used to calculate the percentage of dust attributed to each source. Pass times calculated from time study 

data collected at each mine were used to weight the contribution of each source. For example, if 55% of the total time 

to complete a pass across the face can be attributed to the 
 

tail-to-head pass, then tail-to-head shearer dust levels would 

receive a weighting of 55%, while head-to-tail shearer dust 

along with shield dust would receive a 45% weighting. Contribution levels from the surveys where shield and shearer 

data was collected are displayed in Fig. 4. The percentage of 

dust contributed by the shearer was 43% and remained the 

largest source of dust on the face but decreased by 10% when 

compared to the source contribution data (Fig. 5) from the 

1990s study. Improved directional spray systems coupled with 

higher face velocities have resulted in keeping fugitive dust 

close to the face and out of the walkway. 

Figure 4 

Average dust contributions from major dust sources from the 

2000s surveys. 

Figure 5
	

Average dust contributions from major dust sources from the 

1990s surveys. 

Higher production levels, along with a 39% increase in 

the width of longwall panels, have resulted in a dramatic 

increase in the number of shields advanced and the amount 

of coal passing through the stageloader crusher, as seen by 

the increased potential for dust exposure from shield and 

stageloader sources. 

Significant increases in coal extraction rates have occurred over the last 10 years and, consequently, the potential 

to liberate respirable dust is much greater. Mine operators 

have made substantial strides in the application of dust control technology.Although average shift production rates rose 

approximately 53%, dramatic reductions in average dust 

levels, between 20% and 58%, were realized at each face 

sampling location when dust levels were compared to the 

1990s study. Significant increases in both face air velocity 

and quantity, along with a vastly improved directional spray 

system, help create an envelope of clean air in the walkway 

around the shearer, resulting in lower dust levels. n

Disclosure 

The findings and conclusions in this report are those of 

the authors and do not necessarily represent the views of 

the National Institute for Occupational Safety and Health.

Mention of any company or product does not constitute endorsement by NIOSH. 

References 

Colinet, J.F., Spencer, E.R., and Jankowski, R.A., 1997, “Status of dust control technology on U.S. longwalls,” Proceedings of the 6th International 

Mine Ventilation Congress, May 17-22, 1990, Pittsburgh, PA, Chapter 

55, pp. 345-351. 

Energy Information Administration, 2007, Annual Coal Report 2007, Report No. DOE/EIA 0584, p. 17. 

Fiscor, S.J., 2009, “Total number of longwall mines drops below 50, US 

Longwall Census,” Coal Age, February, p. 24. 

Jankowski, R.A., and Colinet, J.F., 2000, “Update on face-ventilation research for improved longwall-dust control,” Mining Engineering, 

March, pp. 45-52. 

MSHA, 2009,“Program evaluation and information resources,standardized 

information system,” Arlington, VA: U.S. Department of Labor, Mine 

Safety and Health Administration. 

Niewiadomski, G.E., 2009, Mine Safety and Health Administration, private 

communication. 

Tomb, T.F., Ondrey, R.S., Stolz, R.T., Haney, R.A., Chiz Novakowski, D.L., 

Atchinson, D.J. and Gerbec, E.J., 1992,“Evaluation of respirable dust 

control on longwall mining operations,” SME Transactions, Vol. 288, 

pp. 1874-1878.