INVESTIGATION INTO THE PRACTICAL USE OF BELT AIR AT US LONGWALL OPERATIONS 

R. B. Krog, NIOSH, Pittsburgh, PA 

C. J. Bise, West Virginia Univ., Morgantown, WV 

ABSTRACT 

The use of belt air as an intake source at longwall operations has 

greatly changed over the past decades. The practical considerations 

for the use of belt air are controlled by a variety of factors including 

airflow quantity and velocity, coal methane content, methane 

desorption rates, coal mining rate, belt length, stopping leakage, and 

the number of gateroad entries. 

At longwall operations, the advantages and disadvantages of belt 

air are different for gateroad development and longwall panel 

extraction. During gateroad development, the use of belt air to 

ventilate the working section will reduce the leakage from the intake to 

the belt compared to the belt air being ventilated outby the working 

sections because of lower pressure differentials. A greater quantity of 

airflow will reach the last open crosscut with belt on intake than outby, 

given the same amount of pressure and airflow available at the mouth 

of the section. 

This paper will investigate the current ventilation practices 

regarding the use of belt air during gateroad development and longwall 

panel extraction. Operating considerations regarding air quantities and 

pressures to deliver the required airflow will be investigated using 

ventilation network modeling. 

INTRODUCTION 

In December, 2007, the Technical Study Panel on the Utilization 

of Belt Air released a report concerning the use of belt air in US coal 

mines (Mutmansky JM, et al., 2007). The panel’s report covered a 

wide range of topics and their recommendations should be considered 

in all longwall ventilation systems. The ventilation system for each 

longwall primarily depends on the number of entries used in the 

gateroad development. As of February, 2008, there are approximately 

48 operating longwall panels in the United States mining coal (Fiscor, 

2008): 

• 5 – Four-entry (Blue Creek - Mary Lee seams in Alabama / 

Pocahontas #3 seam in Virginia / Powelton seam in West 

Virginia) panels 

• 39 – Three-entry panels 

• 4 – Two-entry (Utah) panels 

The four-entry gateroad longwalls are characteristically located in 

the gassiest coal seams in the United States. To handle high methane 

emissions during development, the outer two entries are placed on 

return air with the middle two entries on intake air. 

The most common three-entry system generally consists of a belt 

entry (ventilating the working section or not), a middle intake, and a 

dedicated return (Figure 1). Belt air can either be directed to the 

working section or not. For the rest of this paper airflow in the belt that 

is sent to the working section will be called ‘belt air’ and airflow in the 

belt that is not used to supply the working section but moving away, 

will be called ‘belt outby’. The middle travelway entry may or may not 

have an installed track but is the primary escapeway unless trolley 

haulage is being used. 

All two-entry gateroads are located in Utah where ground control 

issues preclude the use of developments with more than two entries. 

The yielding pillars that are required to control possible bump 

conditions cannot easily and safely be developed with a three-entry 

system. During development, the belt is located in the return and the 

travelway is in the intake. During panel extraction both entries are 

used to supply intake air to the end of the longwall section. It is 

important to remember that there are several safety considerations that 

must be instituted as conditions for granting a petition for modification 

to allow the belt entry to be used as a section return on development 

and as an intake split on retreat. 

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Return entry

Last Open Crosscut

Belt entry with air to working section

Leakage

Intake entry

Figure 1. Model layout (belt air used to ventilate working section). 

The airflow requirements for gateroads are controlled by a 

number of factors, primarily methane emissions at the face and along

the solid ribs. Emissions from the active face are assumed to be 

independent of the length of the gateroad and require sufficient fresh 

airflow at the last open crosscut for dilution. If the intake air contains 

methane, a greater airflow is required. 

For shorter gateroads, development methane liberation in the 

face area is the primary factor influencing airflow requirements. As 

gateroad distance increases, however, the exposed rib length 

increases and a greater amount of methane flows into the ventilation 

system mainly from the outer coal ribs. This methane inflow rate is a 

function of the coal’s methane content and desorption rate. However, 

for long gateroads, rib emissions can far exceed the methane liberated 

at the development face. In this case, the total amount of air available 

at the section mouth for dilution of the rib emissions limits gateroad 

development distance. All of these methane emission sources can be 

affected by pre-mining or in situ methane drainage. 

Model set up 

VnetPC 2007 (Mine Ventilation Services, Fresno, CA) ventilation 

simulation software was used to analyze gateroads of various lengths 

using 300-meter long segments (984-ft) each with 6 crosscuts. Total 

pressure across the mouth of the section was held constant at 1 kPa 

(4.1 inches water gauge). Entry sizes of 4.7 m x 2.4 m (15.5 ft x 8 ft) 

or 6.1 m x 1.82 m (20 ft x 6 ft) both yield a similar resistance of 0.025 

Ns2

/m8 (22.4 x10-10 in·min2/ft6) per 300-m (984-ft) segment using 

common k-factors (Hartman et al., 1997). The belt entry because of 

the high equipment blockages was given a resistance 20% higher 

0.030 Ns2

/m8 (27.9 x10-10 in·min2/ft6) than the other entries. Stopping 

resistances were set at 2000, 2500, 3500, 5000, 7500 and 10,000 

Ns2

/m8 (179, 223, 313, 448, 671 and 895 x10-10 in·min2/ft6) to represent 

poor to excellent stopping construction (Oswald, 2008). Total lengths 

of gateroads modeled ranged from 300 m (984 ft) to 6300 m (20,670 

ft). Crosscuts were set on 50-m (164-ft) centers with 6 stoppings 

grouped together to indicate standard gateroad crosscut layouts. 

Longer 60-m (197-ft) centers were also modeled to indicate the 

longwall operation with crosscuts farther apart, but the results did not 

differ that much from the basic case if a higher stopping resistance was 
used. For example, six-5000 Ns2

/m8 (448 x10-10 in·min2/ft6) stoppings 

are almost identical to five-3500 Ns2

/m8 (313 x10-10 in·min2/ft6) stoppings 

if placed in parallel over the same 300-m (984-ft) segment (Table 1) 

where equivalent parallel resistance is equal to stopping resistance / 

(number of stoppings)2

. 

Table 1. Equivalent parallel resistances. 

Resistance

Ns2

/m8 654

(50 m apart) (60 m apart) (75 m apart)

10000 278 400 625

7500 208 300 469

5000 139 200 313

3500 97 140 219

2500 69 100 156

2000 56 80 125

Parallel Stoppings 

AIRFLOW AT THE LAST OPEN CROSSCUT 

The amount of airflow reaching the last open crosscut is 

controlled by several factors: 

1. Number of entries and their layout. 

2. Stopping resistance. 

3. Number of stoppings. 

4. Entry resistance. 

5. Pressure differential across the entries. 

6. Limitations in entry velocities or pressures across stoppings. 

With the same pressure differential at the section mouth, a threeentry system can deliver more air to the last open crosscut using ‘belt 

air’ towards the working sections rather than ‘belt outby’ the face 

(Figure). Using ‘belt air’ to ventilate the working sections reduces the

quantity of leakage from the middle intake into the belt, but increases 

the possibility that the belt entry may eventually carry more airflow than 

the intake or be at a higher pressure relative to the intake. This 

establishes a limit to the maximum gateroad length that can be 

developed with the belt on intake air. Figure illustrates that a 

maximum development distance of 3300 m (10,800 ft) is obtained 

when placing the belt entry on intake air and using a stopping 

resistance of 2000 Ns2

/m8 (179 x10-10 in·min2/ft6). For gateroad lengths 

exceeding 3300 m (10,800 ft), total pressure or airflow in the belt entry 

exceeds those values in the intake entry. For all six curves, the 

resistances of the entries are shown in the previous section and the 

pressure at the mouth of the section is 1 kPa (4.1 in w.g.). The relative 

pressure of the belt to the intake was 75% for the ‘belt air’ curves and 

20% for the ‘belt outby’ curves. As the stopping resistances increase 

or if the belt entry is placed on ‘outby’ airflow, maximum development 

distances can increase. The ideal cases of no leakage through the 

stoppings are also shown in Figure 2. 

In addition to stopping resistance, maximum gateroad 

development length is impacted by the pressure differential between 

intake and belt entries at the section mouth. Figure 3 shows the 

maximum gateroad development distance that keeps intake entry 

airflow higher than belt entry airflow. The percentages in the graph are 

the total pressures in the belt entry relative to those in the intake 

airway measured at the section mouth. “LOC” (last open crosscut) and 

“Mouth” refer to the locations that limit gateroad development. 

Total pressure in the belt airway cannot be lowered too much; in 

that a lower relative pressure translates to a lower belt airflow 

measured at the section mouth. With total pressure in the belt entry at 

70% of the total pressure in the intake entry, gateroad development is 

not restricted by the high belt airflow at the last open crosscut but, 

rather, by low belt airflow at the section mouth. Using the guidance of 

the Technical Study Panel on the Utilization of Belt Air of a minimum 

air velocity of 100 ft/min (0.5 m/s) and an entry opening of 11.2 m2

 (120 

ft2

), the minimum airflow quantity is calculated to be 5.6 m3/s (12,000 

cfm) at the section mouth for these models. Using the above example 

of the belt entry pressure at 70% of the intake entry pressure and 

stopping resistances of 7500 Ns2

/m8 (671 x10-10 in·min2/ft6), the 

maximum gateroad development is not limited to 6000 m (19,700 ft) by 

airflow at the LOC, but by the low airflow at the mouth of the section 

when the gateroad is developed to 4800 m (15,700 ft). 

0

10

20

30

40

50

60

70

80

2000 3000 4000 5000 6000 7000

Development (m)

Airflow at Last Open Crosscut (m3/s)

Belt Outby 10,000 x Ns2/m8 

Belt Outby 2000 x Ns2/m8 

Belt Air 10,000 x Ns2/m8 

Belt Air 2000 x Ns2/m8 

Belt Air No Leakage

Belt Outby No Leakage

Figure 2. Airflow at last open crosscut with belt on intake and 

return with different stopping resistances (Ns2

/m8) 

The maximum distance for gateroad development occurs when 

both the restriction on airflow at the last open crosscut and minimum 

airflow entering the belt at the mouth of the section occur at the same 

time. The 75% LOC line represents the maximum development 

distance while balancing both requirements at the LOC and mouth of 

the section. In the above example of 7500 Ns2

/m8 (671 x10-10

in·min2

/ft6) stoppings, if the total pressure in the belt is 75% of the 

intake at the mouth of the section, the maximum development was 

calculated to be 5100 m (16,700 ft), not 4800 m (15,700 ft). 

The purpose of the gateroad development is the mining of the 

subsequent longwall panel. Ventilation of the gateroad development 

should not be the only consideration for using 3 or 4 entries. 

Ultimately, the gateroads provide important ventilation flow paths 

through the worked-out area and have significant impact on the 

bleeder system performance. While this paper covers belt air issues 

on gateroad development, the important future use of the gateroad and 

the bleeder system should be considered. 

0

2000

4000

6000

8000

10000

12000

0 1000 2000 3000 4000 5000 6000 7000

Gateroad Develpoment (m)

Stopping Resistances (Ns2/m8

)

90% LOC

80% LOC

70% LOC

70% Mouth

75% LOC

Figure 3. Theoretical maximum gateroad development using belt air 

on intake with relative pressure differentials and variable stopping 

resistances. 

LIMITATIONS OF BELT AIR 

Using belt air to ventilate the working sections does make it 

possible for a higher percentage of intake air to reach the last open 

crosscut because leakage is reduced. However, a new problem arises 

with the belt entry carrying more air than the intake entry. 
Using the same model parameter as before, the maximum 

gateroad length that can be ventilated using belt air is controlled by two 

factors: 1) leakage into the belt and 2) methane emissions. Excessive 

leakage into the belt near the start of the section and continued 

leakage from the intake into the return can cause the belt to be at a 

higher relative pressure than the intake at the end of the gateroad. 

Eventually the belt will be supplying a greater airflow than the intake to 

the working section, contrary to regulations (CFR 75.350(b)(6)) [Code 

of Federal Regulations, 2008]. When belt air starts leaking into the 

primary intake, the major concern is that a belt fire will contaminate the 

intake air split with CO and smoke and make escape more difficult. 

The belt entry will have a higher resistance than the intake entry due to 

obstructions such as belt structure, belt take-ups, etc. Air from the belt 

entries will leak into the intake entries long before the belt is carrying 

more air than the intake as shown in Figure 4. Figure 5 shows that 

once leakage into the return from the intake approaches 41%, the 

ventilation system, regardless of stopping resistance, has a problem 

with the belt entry being at a higher pressure than the intake. 

Figure 4. 4200-m model with 1 kPa of pressure at the mouth of the 

section and 5000 Ns2

/m8 stoppings showing leakage from belt into 

intake entry (0.02 and 0.04 m3

/s) before belt entry transporting more 

airflow than intake. 

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

50%

0 1000 2000 3000 4000 5000 6000

Limit of Development (m)

Leakage %

10000 Ns2/m8

7500 Ns2/m8

5000 Ns2/m8

3500 Ns2/m8

2500 Ns2/m8

2000 Ns2/m8

Figure 5. Gateroad development limit using belt air at 75% of 

pressure of intake entry with different stopping resistance, leakage 

total is from intake into return. 

The use of point-feeding the belt entry is a common practice and 

a beneficial one for shorter gateroad developments. This paper is 

concerned with calculating the maximum distance that a gateroad can 

be developed if ventilation is the limiting factor. The use of pointfeeding will decrease the maximum distance that can be ventilated 

before the belt is at a higher pressure then the intake. For this reason, 

point-feeding is not modeled in this paper. 

Increased Belt Resistance 

The belt resistance was set at 20% higher than the other two 

entries but the belt resistance was also modeled at 0% and 40% 

greater than the other two entries to represent the increased 

obstruction of the belt assemblage. There was no significant change 

to the pattern of airflow in the belt or in the leakage quantity from belt 

to intake. The two controlling factors for the development of very long 

gateroads are stopping resistance and pressure differential at the 

mouth of the section. 

The Mixing Problem 

The ventilation models show that a higher percentage of airflow 

will reach the working section if the belt is placed on intake rather than 

return assuming similar resistances. The methane loading of the 

intake air will be quite different and will affect the ability to ventilate the 

active workings. The main assumption is that little methane will enter 

into the middle intake while methane will bleed into the outer entries off 

of the solid coal rib. When the outer belt entry is used to ventilate the 

working section, methane emissions from the rib will be carried to the 

active face and can increase the starting methane concentrations at 

the working section. Higher starting methane levels for the combined 

intake and belt air would require a higher airflow quantity to dilute the 

methane liberated in the working places. The final methane emissions 

at the last open crosscut can be calculated by the following formula: 

(CI ×QI )+ (CB ×QB ) CF = QI +QB

Where: 

CI

 = Intake concentration 

QI = Intake air quantity 

CB = Belt concentration 

QB = Belt air quantity 

CF = Concentration where the belt air and intake air mix 

The quantity of methane released by the coal transported on the 

belt changes during panel development and panel extraction. The 

quantity of coal mined by the continuous miner is less than 10% of 

what a shearer produces and is more cyclical during the shift. 

Methane emission rate of the mined coal on the belt during panel 

development is low when compared to the rib emissions rate. For 

example, 26 m3

/s (55,000 cfm) supplied by the intake track entry, 

compared to 14 m3

/s (30,000 cfm) of intake air and 12 m3/s (25,000 

cfm) of belt air, may not have the same diluting ability. Assuming the 

intake track entry has a methane concentration of 0.1%, and the belt 

0.3%, the final mixed methane concentration will be 0.19% using the 

above equation. This represents a reduction of 10% of the fresh air to 

dilute the working places of methane on a per m3

 (ft3) basis but this 

example does not have a higher airflow quantity usually associated 

with using belt air to ventilate the working sections. In gassy 4-entry 

longwall operations, adverse rib emissions preclude the practice of 

bring outer entry airflow towards the working section. 

Panel Extraction 

During longwall panel extraction, the belt can be fully loaded with 

coal that can add a significant amount of methane to the air used to 

ventilate the longwall headgate. With so much methane being 

liberated by the coal, it may be more appropriate to ventilate the belt 

airflow outby the longwall section and convert the gateroad 

development return entry into a secondary intake. This has a number 

of benefits, such as increasing safety with two semi-isolated 

escapeways and supplying a greater quantity of airflow to the 

headgate end of the longwall face at a higher pressure. 

For example, a longwall panel with a length of 4270 m (14,000 ft) 

was initially ventilated with belt air and one intake entry. Upon longwall 

panel startup, airflow was reduced to the return entry to maintain 

adequate airflow across the longwall face. Soon thereafter, a problem 

arose with high methane concentrations in the belt entry once the 

shearer had been operating for one cut cycle to load the belt with coal. 

A methane concentration of 0.7% on 12 m3

/s (25,000 cfm) airflow at 

the working section of the belt entry necessitated a major change to 

the ventilation system (Figure 6). The belt was switched to return 

airflow and the return entry was converted into a secondary intake. 

This enabled 62 m3

/s (131,000 cfm) to reach the headgate end of the 

longwall face rather than 50 m3

/s (106,000 cfm) before the switch 

(Figure 7). The methane emissions from the solid coal rib of the 

converted return entry are now coursed to the longwall face. The 

higher air quantity outweighed this added methane loading. 

Entry Resistance 

Entry resistance plays a significant role in determining how much

air is delivered to the last open crosscut. By doubling the resistance of 

the entries, the expected flow rate should decrease to approximately 

71% of the original airflow. 
C

R C

12

14

38

21

26

Belt air to headgate 0.7% CH4

Gob

Figure 6. 4270-m longwall panel at startup with belt air. 

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C

12

24

38

28

38

Gob

Figure 7. 4270-m longwall panel at startup with dual intakes. 

R

P Q ∝

In the ventilation models, the stopping resistances are kept 

constant and therefore the system will have a higher leakage 

percentage. The above simplification will only hold true if stopping 

resistance also increases by the same ratio as the entries’ resistances. 

With the stopping resistances kept constant and the entries’ 

resistances doubled, the calculated airflow at the last open crosscut 

can be reduced to less than 50% of the base case. 

CASE STUDY 

A three-entry longwall panel was converted from using belt air on 

intake to return for gateroad development on subsequent panels. The 

mine indicated that everything was kept the same in the development 

of the two adjacent gateroads except for reversing the airflow in the 

belt and the higher pressure at the mouth of the section of the new 

gateroad. This conversion was possible because the mine had just 

connected to a new ventilation shaft. The initial measured airflow 

distribution is shown in Figure 8. The gateroad was 3670 m (14,000 ft) 

in length and had 65 crosscuts. The layout placed the belt in #1 entry, 

the intake in #2, and the return in #3. The supplied airflow to the last 

open crosscut was 26 m3

/s (55,000 cfm), with leakage from the intake 

entry into the belt entry. While there was still more airflow in the intake 

for the last 600 m (1970 ft), the 3600-m (11,800 ft) ventilation model 

showed that belt air may have been leaking into the track entry (as 

previously shown in Figure 4). 

The individual stopping resistances utilized were chosen to be 

3500 Ns2

/m8 (313 x10-10 in·min2/ft6) using a 3600-m (11,800 ft) VnetPC 

ventilation model constructed before. The modeled airflow pattern 

corresponds closely with Figure that represents both the measured 

airflow patterns of the actual 3670-m (12,000 ft) gateroad and the 

3600-m (11,800 ft) ventilation model. The second ventilation model of 

the gateroad shows the same 3600-m (11,800 ft) ventilation model 

gateroad but with the belt on return (Figure 9). The airflow at the last 

open crosscut reduced from 26 m3

/s to 16 m3/s (55,000 cfm to 34,000 

cfm). To deliver original airflow of 26 m3

/s (55,000 cfm) to the last 

open crosscut, the pressure differential at the mouth of the section had 

to be increased to 1010 Pa from 432 Pa (4.1 from 1.8 in w.g.). 

C

R

42

26

33

9

16

3

12

14

Figure 8. 3670-m gateroad with belt air on intake, plus 3600-m 

ventilation model (432 Pa). 

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31

16

48

17

15

13

4

20

Figure 9. 3600-m ventilation model with belt on return (432 Pa). 

Figure 10 shows modeled airflows with a pressure differential of 

1010 Pa at the section mouth and stopping resistances of 3500 Ns2

/m8

(313 x10-10 in·min2

/ft6) , 26 m3/s (55,000 cfm) at the last open crosscut, 

and the belt entry outby. There is too much leakage in Figure to match 

the field-measured airflow distribution pattern shown in Figure 11. 

Modeled stopping resistances were increased to 5000 Ns2

/m8 (448 x10-

10 in·min2

/ft6) to better match the actual airflow pattern after resealing 

the stoppings as shown in Figure 12. The mine site was contacted 

again and the authors were told that a second sealant coat was 

applied to the stoppings months after installation to reduce the air 

leakage that occurred because of the higher pressures and stopping 

deterioration. The stoppings were constructed using the same material 

but the higher pressures and leakage necessitated resealing. 

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49

26

73

24

23

19

5

31

Figure 10. 3600-m ventilation model pressure requirements to supply 

26 m3

/s at the last open crosscut using original stopping resistances of 

3500 Ns2

/m8 (1010 Pa). 

In this case study, converting the belt entry to return increased the 

pressure and airflow requirement from 42 m3

/s @ 432 Pa (89,000 cfm 

@ 1.8 in w.g.) to 62 m3

/s @ 835 Pa (131,000 @ 3.4 in w.g.) at the 

mouth of the section. This calculates to a 185% increase in static air 

power (Quantity x Pressure) to ventilate the same length gateroad. If 

the original stoppings were not resealed, the static air power would 

have increased 306% (73 m3

/s @ 1010 Pa) (155,000 cfm @ 4.1 in 

w.g.). Higher pressure requirements at the mouth of the gateroads will 

also result in higher leakages in the mains and submains and a further 

increase in pressure on the total mine ventilation system. 

Belt in middle entry for very long gateroad developments 

If an ideal three-entry gateroad is developed with equivalent 

resistances in all entries, no stopping leakage, intake air supplied 

through the belt entry, and with the airflow evenly split between the two 

intake entries, 80% of the head loss will occur in the return entry. The 

same holds true for a single intake entry with two return entries. This 
physical limitation of three-entry gateroads is the real restrictive factor 

in their development – no matter which choice, one entry will end up 

carrying the entire section airflow and have high head loss. 

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17

45

26

62

19

5

12

31

Figure 11. 3670-m gateroad with belt on return, better stoppings. 

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18

44

26

62

18

4

14

30

Figure 12. 3600-m ventilation model with belt on return, better 

stoppings (835 Pa). 

For example, consider a three-entry gateroad where Q m3

/s is 

brought up both the belt and intake entries. The return is required to 

remove 2Q. The head loss is = RQ2

 + R(2Q)2 = 5 RQ2. Alternately a 

four-entry system with two intakes would move Q each and the two 

returns would also remove Q each. The head loss is = RQ2

 + RQ2 = 2 

RQ2

 or 40% of the head loss compared to the three-entry example. A 

four-entry system could, therefore, theoretically develop a greater 

distance because of more airflow can be moved with less pressure and 

less leakage by the shared entries. This is the case for gaseous 

longwall operations choosing four-entry gateroads. 

An alternative way to develop very long gateroads is to place the 

belt in a middle entry as a low airflow belt outby entry or belt air to the 

working section entry (Figure 13). There is no difference to the 

quantity of airflow reaching the last open crosscut if the middle belt is 

operated on belt air or outby. The leakage into the belt from the intake 

entry will closely match the leakage from the belt to the return. One 

leakage path from the intake is eliminated and air leaking from the 

intake to the return has to pass through two sets of stoppings. Airflow 

would have to pass through a stopping to move from the intake into the 

middle belt entry and then pass through a second stopping to reach 

the return. There is no theoretical limit on development length when 

using the belt in the middle entry (Figure 14), just a practical limitation. 

The ‘Belt Middle’ designation is the example of the belt located in the 

middle entry ventilating airflow to the working section. The belt would 

have to be moved over to an outer entry after development before 

longwall panel extraction could commence. This is a costly and time 

consuming process but would allow for the development of extremely 

long gateroads. The final use of the gateroad to ventilate the longwall 

panel and bleeder system should also be evaluated. A longwall 

operation using a four-entry yield-stiff-yield pillar layout developed the 

gateroads with the belt in the #2 entry and then used the shearer to 

mine the yield pillar during panel extraction. 

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Return entry

Last Open Crosscut

Belt entry with air to working section

Leakage

Intake entry 

Figure 13. Belt in middle entry on intake. 

0

10

20

30

40

50

60

70

2000 3000 4000 5000 6000 7000

Development (m)

Airflow at Last Open Crosscut (m3/s)

Belt Outby 10,000 x Ns2/m8 

Belt Outby 2000 x Ns2/m8 

Belt Air 10,000 x Ns2/m8 

Belt Air 2000 x Ns2/m8 

Belt Middle 10000 x Ns2/m8 

Belt Middle 2000 x Ns2/m8 

Figure 14. Airflow at last open crosscut for different belt locations (#1 

entry or #2 middle entry), belt air used to ventilate the working section 

or belt outby, and for different stopping resistances Ns2

/m8. 

SUMMARY 

The use of belt air to ventilate the working section during gateroad 

development can increase the total airflow at the last open crosscut but 

with possible disadvantages. The physical ability to move more airflow 

to the last open crosscut can outweigh the added methane emission 

from the solid coal rib so long as it is not displacing fresh intake air. 

For long gateroad distances or poor stopping resistances, there could 

be situations where the belt air leaks into the intake entry. When belt 

air starts leaking into the primary intake, the major concern is that a 

belt fire will contaminate the intake air split with CO and smoke and 

make escape more difficult. This paper showed that ventilation 

pressure at the section mouth and stopping resistances are the limiting 

considerations for the maximum length gateroads that can be 

developed using intake belt air. In a case study a three-entry gateroad 

that converted from belt air ventilating the working section to belt 

airflow outby the working section increased the air power requirements 

at the mouth of the gateroad 185% to maintain the same airflow at the 

last open crosscut. 

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. 

REFERENCES 

1. Code of Federal Regulations, Title 30, Part 75:350(b)(6),

http://www.msha.gov/30cfr/75.350.htm. 

2. Hartman HL., Mutmansky JM., Ramani RV., Wang YJ. (1997), 

Mine Ventilation and Air Conditioning, Wiley Interscience. 

3. Fiscor S., (2008), US Longwall Census 2008 – February 2008, 

Coal Age, February 2008, 28 pp. 

4. Mutmansky JM., Brune JF., Calizaya F., Mucho TP., Tien JC., 

Weeks JL., (2007) The Technical Study Panel on the Utilization of 

Belt Air and the Composition and Fire Retardant Properties of Belt 

Materials in Underground Coal Mining, December 1999. 

http://www.msha.gov/beltair/BeltAirFinalReport122007.pdf. 

5. Oswald N., Prosser B., Ruckman R., (2008), Measured values of 

coal mine stopping resistance, 12th U.S./North American Mine 

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