Dev£~lopment of coal mine 


fac(~ ventilation systems 


dUI"ing the 20th century 


DUring the 20th century, the increased emphasis 

on worker health and safety and the advent of 

new mining equipment and methods led to many 

changes in mine face ventilation practices. Efforts by 

government and private industry to improve and modify 

ventilation practices resulted in better health and safety 

conditions for workers. 

This article focuses on U.S. Bureau of Mines (USBM) 

and National Institute for Occupational Safety and 

Health (NIOSH) research to examine factors that had 

a significant influence on mine (ace ventilation design 

during the past century. Several "milestone" events are 

discussed along with the impact they had on worker 

health and safety. Significant ventilation research efforts 

by government and private. industry are presented, This 

brief ventilation history highlights innovative face ventilation designs and a consistent commitment to mining 

health and safety, 

Ventilation bas always been a concern in underground 

coal mining. For many years, there was no appreciation 

of how ventilation could be used to remove harmful contaminants from the air or how to control airflow quantities. 

The first known problems '.vilh ventilation date back to 

the 14th century, when it was recognized that lack of air 

was a major impediment to the expansion of mines. The 

common method of solving ventilation problems at that 

time was to abandon the e.xisting mine and start a new 

one nearby, 

FIGURE 1 

Rescue woril:ers at the Derr Mine explosion, Jacobs Creek. 

PA. Doc.19, 1007. 

'IGURI2 


Historical summary of the Jacohs Creek Mine disaster 

(Humphrey, 19601. 

December 19. 1901: Dart Mine, Jacobs Creek. 


Pa.; 239 Killed 


I Pro", ,"'tn(c il"pt'ctor'. report, 1907. pp, .rt'!iii-z.zrii, 


869-8iO ) 

At 11::30 In th~ morning· •• liD an'iul t'tIlIlbJ[nl; 

followed by a loud r~port alld n oollcu,,,,,i,,n thll.t shook 

the of'or.by building:; "'4S felt \vlthln n radius uf 

I\e"erul nllle~, The Dan mlne wns lle\'er deemed 1\ 

rery dangerous mine as It ,ener!1ted only 11 small percentage of gn", Qud was worked wHh open lights, '!"be 

explosion bad'· •• terrillc (0n.'6 •• t, Progress by rescuers (fig, 4) wns rery slow ol\'lng to the fnet 

rhat all the IltoPllings were hlowo IIlIt, ••• Only 

one man es<:uIMMi ••• ; be was on h1s WilY to the en

gine roulII for oil, ••• Thl' cause may hllve been 

the projecthm of !lnme Into a gliseQUlf and dn,"Itr ntmosilhere ••• hy 0.0 III)tO light or a blowD-t')ut shot. 

• •• Tbe lCysttm ot workings· •• dOl'S not pro,-Ide 

Cur l'ffident "enrJlntlon •••, We re<.'Onllllend ••• 

the de,'el1lpment on n four-entry system, ••• tbat l'I~ntllnthJU be l:uotwlled by o,-erc:J,st1<; Instelld uf dooN!, 

• •• thot IIl1mele!l"~ explt>I'II'-~ he used tor all blastIng, •• • thllt competent IIhot IIrprs ••• prepare, 

!'Ilnrgf', 1\1\11 1\1'1" the sbon litter wurkmen are out of 

Ihe WhIP, ••• thnt all stl'mmlnl; be with clay or 

uther i11('OIllbu>'tlhle matl"rinl.·· • thllt a water 

SYI!tl'1D be In,.tailNl tur wl'tUng and lnyllll: the dust. • •• tlUlt nil 31."C\lrnulntlonl> of dust be IOllded out. 

• • • tlult the mine he worked eJll,:dust~ely 'lll"lth lockf'd 

l'I;tfl'I y hemp!!• ••• thllt eno1lgh Hrt'boAAfoli "hould be 

pmpln~"' 1 It) JUllke t'nreiul eJll,:lImlnntl(lo~ of tbe mine 

• ••, Qnd that thp mine tOM"mllll IIp\'nte thl" wbole 

ut hlii tlme.1O hl:1 !lutle!! II !! descrllH>d hrlnw lind mnlntllin ri~ld dillclpllne, ••• 

­

Ventilation in the early days of coal mining was accomplished by means of a natural draft. created principally 

by a difference in tbe weights of columns of air between 

the intake and return openings. Later, in the 18th and 19th 

centuries, a furnace was 

introduced underground 

to increase the updraft in 

tbe return shaft, This allowed fo r a larger quantity 

of air in circulation, When 

mines went deeper and 

became larger. mechanical 

ventilation became necessary and was first accomplished by steam-driven 

fans, These fans became 

more prevalent as furnaces 

were prohibited in underground mines, especially 

after tbe Avondale disaster 

in Pennsylvania in 1869 

(Roy, 1876), Eventually. 

these fans were replaced by 

more powerful, electrically 
driven centrifugal fans in the 20th century. (Forbes, 1929; 

Redmayne,1911). 

As mines went deeper, underground explosions began 

to occur. The source of the new danger was a mysterious 

gas called firedamp that exploded violently when it came 

in contact with open lights. Persons working in the vicinity of such ignitions were often killed by the force of the 

explosion or were burned to death. It was recognized in 

the 17th centwy that the buildup oftbis gas was tbe main 

cause of the underground coal mine explosions. But there 

was no way to prevent this gas. known as methane, from 

entering the mine because it was continuously liberated 

from the coal seam. It was not until the 20th century that 

ventilation techniques would be used to control the levels 

of methane. 

Conversely, coal dust was not recognized as a danger 

until the early 19th century (Redmayne, 1911; Lee, 1971). 

The health hazard from this dust was thought to be related to silica o r silicosis. It was not until 1934 that coal 

dust was recognized as a cause of a progressive and fatal 

respiratory disease in Britain. It was 30 years later before 

coal dust would be officially recognized as a health bazard 

separate from silicosis in the United States through the 

Federal Coal Mine Health and Safety Act of 1969 (Lee, 

1971). In the interim, ventilation was not thought of as a 

means to control this dust. The application of water was 

the primary means to reduce airborne dust levels. 

Up to and throughout the 20th century, mine explosions killed hundreds of miners at a time. The public 

outcry became loud enough in the United States that 

action was taken to form an agency that 

wouJd investigate ways to make mining 

safer. While discussions of the formation 

of this new agency were ongoing. four 

large underground explosions occurred 

in a short time period: 361 coal miners 

were killed in Monongah, WV. on Dec. 

6,1907; 239 were killed two weeks later 

at Jacobs Creek, PA (Figs. 1 and 2); 154 

were killed at Marianna, PA, Nov. 28, 

1908 and 259 were killed at Cherry, IL, 

on Nov. 13, 1909 (Kirk,I996). 

As a result of these explosions and 

fatalities, the U.S. Bureau of Mines 

(USBM) was formed on JuJy 1, 1910. Pan 

of the USBM mission was to investigate 

mine explosions and enhance the safety 

of miners by preventing accidents and 

imprOving working conditions in mines 

(Kirk, 1996). The USBM conducted 

many research investigations on underground coal mine ventilation. This 

research continues today at the National 

Institute for Occupational Safety and 

Health (NlOSH) under lhe Centers for 

Disease Control, U.S. Department of 

Health and Human Services. It is understood that ventilation research has 

been conducted by many agencies., public 

and private, worldwide. This overview 

focuses on research conducted by the 

USBM until 1997 and subsequently by 

NIOSH. It gives a picture of how this 

research has impacted face ventilation 

systems, which has led to safer mining 

with fewer fatalities and injuries due to 

explosions and face ignitions. This reo 

search has been shaped by a commitment 

to make mining safer while providing 

ventilation techniques that complement 

current mining technology. 

USBM ventilation research 

from incoption through tho 1940s 

Much of the early interest in mine 

ventilation research was related to a 

concern for the physical well-being of the 
miners who worked underground. The effects of dust and 

gases on the workers were understood and publicized, as 

were the impacts oftemperature and humidity of the ventilating air. Guidelines were published on recommended 

air velocities at certain air temperatures and humidity 

levels to maximize the comfort of the miner. The cost of 

maintaining the air at these temperature and humidity 

levels and velocities was shown to be recouped through 

the increased productivity of the miner (Sayers and Surgeon, 1922). An early recommendation from the USBM, 

"The quantity in cubic feet of pure intake air flowing per 

minute in any ventilation split should be at least equal to 

100 times the number of men in that split." 

This standard was based on the need to provide a 

working environment that would promote the health and 

productivity of the worker. All of this was accomplished 

by focusing on improving the overall mine ventilation 

system. . 

The lack of adequate and efficient 


ventilation was recognized as the pri­


mary cause of gas ignitions in coal mines. 


It was believed that explosive gas did not 


accumulate in properly ventilated mines 


(Harrington and Denny, 1938). How­


ever, most of the early slUdies to reduce 


methane ignitions were based more on 


removing the sources of ignitions rather 


than improving ventilation. Three of the 


major sources of ignitions were: 


• 	 Use of nonpermissible explosives 


or tbe improper use of permissible 


explosives. 


• 	 Improper installation, maintenance 


or use of electrical equipment. 


• 	 Use of open lights and misuse of 


safety lamps. 


Following the organization of the 


USBM, acceptance and use of permis­


sible explosives had a great effect on 


reducing the number of underground 


explosions. When the original tests on 


explosives were developed, very little 


was known about the mechanism of the 


ignition of methane-air mixtures. The 


USBM considered this one of its most 


fundamental research problems. The 


first approach to solving it was to view it 


as a Hame study. This was based on the 


belief that the longer the flame and the 


longer the time it endured, the greater 


is the chance that such a flame would 


ignite flammable mixtures of gas and air. 


Further methane and coal dust testing in 
 . the 19205, as shown in Fig. 3, studied the 

characteristics of the explosion process, 

such as the shock wave, gaseous products, 

type of flames involved and nature of 

ejected panicles (Fieldner, 1950). 

The danger of methane ignitions due 

to electrical sparks became an issue as 

more electrically powered eq uipment 

was introduced inlo mines. Because of 

this danger, the use of animal haulage or permiSSible storage-banery locomotives was recommended in other than 

pure inlake air and the use of booster and auxiliary fans 

was discouraged (Forbes and Ankeny, 1929; Harrington 

and Denny,l938).The USBM recommended that booster 

or auxiliary fans not be used for supplying air to working 

faces (Forbes and Ankeoy, 1929). Nevertheless-such fans 

were installed in gassy mines regardless of the hazards 

involved, sometimes with disastrous consequences (Harrington and Denny, 1938). It was not until many years later 

that the USBM enforced standards for pennissible fans. 

Open lights were a source of ignition throughout the 

early 20th century. The development of safety lamps in 

the 1800s reduced the danger of ao ignition due to the 

flame of an open light. However, for many years there 

remained a controversy about when it was necessary to 

use the "closed" versus the "open" lights.. This c1assifica­
tion was the precursor to nongassy and gassy mines. 

And, often, it was a question of whether a mine. or part 

of a mine, was gassy or had the potential to accumulate 

dangerous quantities of m~:thaDe gas. Mines were referred 

to as open- or closed-light mines depending on the relative ignition hazard. Additionally, some argued that the 

flame safety lamp was an underground hazard since there 

was the potential to misuse the lamp. There were many 

documented cases of workers taking a safety lamp apart 

underground and attempting to relight them with matches 

(Tomlinson, 1944). Manyexplosions with loss of life were 

due to this practice. Ignitions due 10 open lights became 

less of a problem as permissible electrical lights became 

more prevalent and the Harne safety lamp was delegated 

from a source of light to a means of methane detection. 

FIGURE 3 

Explosion from the Experimental Mine at th e U.S. Bureau of 

Mines Bruceton labo ratory. 

PlGURE 4 

Jey boom cutter used in conventional min ing. 

The first guidelines for ventilation design were presented in 1929.These guidelines included recommended 

airway velocities, minimum volumes of air fo r a split and 

the optimum amounts ofintake air that should reach the 

face. Itwas recognized that a ventilation system would be 

adequate if the following guidelines were followed. Airway velocities were not to exceed 9.1 mlsec (I,8OO fpm ) 

in smooth-lined airways, 4.1 mlsec (800 fpm) in Donnal 

ribbed entries and 3 mlsec (600 fpm) in main baulage 

airways. The minimum 

velocity was to never 

fall below 1 m1sec (200 

fpm). The recommended minimum volume for 

a split of air was 4.7 m3

/ 

sec (10,000 cu ftlmin). 

The amount of intake 

air from the shaft that 

should reach the face 

was recommended to 

be 50 percent, although 

80 percent to 85 percent 

was stated to be more 

desirable and attainable 

through proper installation and construction 

of stoppings:; doors and 

overcasts (Forbes and 

Ankeny, l929). 

The main focus oC 

ventilation studies was 

on proper design of the 

overall ventilation system with emphasis on 

the proper construction 

a?d installation of stoppmgs. doors and overcasts. 
USBM coal mine ventilation research from 1950 

to 1970 

The period between 1950 and 1970 was an important 

turning point in mine ventilation research. Before 1950, 

procedures for improving face ventilation were based 

on actual operating conditions observed in unde.rground 

coal mines. After 1950, many recommendations for 

improving face ventilation were based on controlled 

research experiments conducted in the laboratory and 

underground. .. . 

During this time, conventional an~ contm~o\lS m..m.J:Dg 

methods were used underground, With conUnuous mming becoming more common. Each mining technique 

presented specific ventilation requirements for meth

ane control. One of the first reports of this time period 

focused on the ventilation of a coal face undercut with 

a cutting machine, as shown in Fig. 4. It stressed the i~­

partance of keeping the line brattice close [0 the face an 

order to clear the kerf (undercut) of methane. For blowing brattice, this distance was no more than 1.5 m (5 ft) 

from the face. This practice was emphasized as a way to 

prevent future explosions; by eliminating the methane, 

the possibility of explosions was removed (Stahl and 

Dodge. 1956). 	 . . 

The continuous miner machine changed coal rrurung. 

These new machines advanced working faces rapidly. 

generating coal production tonnages never before seen. 

However, when using a continuous miner, methane was 

­

released more rapidly Crom the face. Additionally, the 

large size of these mining machines made it difficult to 

get enough air to the face to adequately dilute the methane.It became necessary to conduct research to develop 

improvements in face ventilation techniques that C?uJd 

reduce the dangerously high methane conc:nt~atlo~s 

that resulted from continuous mining. Ventilation, 10 

addition to water sprays, was important for dust control 

(Fieldner,I950). However,most studies during this ~e 

focused on ventilation controls to remove methane liberated at the face. 

The greatest problem was the challenge of providing 

sufficient quantities of air to the (ace using line brattice. 

Significant losses in air quantity were known to occur 

between the last open crosscut and the face end of the 

curtain or tubing. Guidelines for installing. line brat· 

lice systems were publicized by the USBM m the late 

1920.. 

,.GUIlI S 

Auxiliary fan used to provide fre.h lir to the faCI. 

The guidelines stipulated that the line brattice be 

constructed from the crosscut to within 1.5 to 1.8 m (5 to 

6 ft) of the face to conduct the air into the room and allow 

it to sweep the face. The line brattice also should be made 

of fireproof canvas material secured to wooden posts, 

anchored at the roof and fioor. The intake side of the 

line brattice should have a smaller, cross·sectional area 

than the return side in order to maintain higher intake 

velocities to correctly sweep the face of any gasses that 

appear. Additionally, it should be constructed as airtight 

as possible, thereby reducing the explosion potential at 

the face (Forbes and Ankeny, 1929). 

Additional work recommended that more durable 

and less combustible materials be used to replace ordinary canvas or jute brattice and ventilation tubes or 

conduits. These recommendations were made to increase 

the life of these materials, as they could be destroyed by 

fire, fungus rot or acid mine water. CoDSide~ation of ~he 

use of plastics, fiberglass, and other ceramtC matenals 

was suggested (Fieldner, 1950). 

Almost all other studies performed during this time 

period focused on face ventilation w~en us~g contin~­

ous miners. Some early recommendatIOns., which are stdl 

valuable today, for improved face ventilation include the 

following (Stahl, 1958; Schlick and Dalzell, 1963): 

• 	 Line brattice can be used effectively to convey the 

proper amount of air directly 10 the Cace if it is properly constructed. 

• 	 The liberation of methane varies considerably from 

location to location. 

• 	 Using a blowing fan and tubing. as shown in Fig. 5, to 

force air to the face is effective for removing methane. 

However the rib where the airfiow passes must be 

kepi wet ~r more dust will be ge.ne r~ted. . 

• 	 Using an exhaust fan and tubmg IS ~ffectlve for 

removing methane Crom the face, proVIded that the 

tubing is kept within 1.5 m (5 ft) of the face. 

• 	 A combination of blowing and exhausting fans works 

effectively under the following conditions: 

. The exhausting tubing should be located close 

to the face and inby the blOwing tubing. 

_The blowing tubing should be located 6.1 m 
(20 ft) or closer to the face but outby 

the exhaust tubing. 

-The two fans should not be balanced to allow 

airflow in the shuttle car entry. 

• 	 The fans used for face v~;ntilation should be permissible with the following guidelines: 

- Blowing fans should be installed on the intake 

side. 

- Exhausting fans should be installed on the 

return side. 

-The quantity of intake air available for face 

ventilation should be larger than the capacity 

of the fan. 

• 	 A blowing fan with a Y-shaped duct with the duct ends 

on either side of the continuous miner terminating 

at the face is effective. The Y-shaped duct is used to 

direct the air to either side of the miner as needed. 

• 	 Recirculation of air is not desirable: 

- When operations are idle, line brattice should 

be used to ventilate the face. 

- Ifthe main ventilation current is disrupted, 

the face ventilation fans should be shutdown. 

Other studies were completed to determine the ventilation properties ofline brattice systems and ventilation tubing. These studies evaluated the friction and shock losses 

for the material types and installation methods of each type 

of ve.ntilation system (Dalzell,l966; Peluso,l968). 

However, probably the most significant study completed during this time period was one that detennined 

the airflow distribution patterns for both blowing and 

exhausting face ventilation systems using line brattice. 

Figure 6 shows the airflow distribution patterns that have 

been established for blowing and exhausting face venti· 

lation systems. This figure shows how the blowing face 

ventilation line brattice, with setback distances of 3 and 6 

m (10 and 20 ft), is effective for removing methane concentrations from the face. However, the airflow palterns 

for the blowing system create turbulence and secondary 

airflow patterns, which are detrimental for dust control. 

It also shows the airflow patterns for the exhausting face 

ventilation system and corroborates the fact that the line 

brahice must be close to the face to remove methane 

effectively. Exhaust ventilation creates less secondary 

airftow and turbulence, particularly at the 3·m (10-ft) 

setback distance, which allows this system to minimize 

dust entrainment. By displaying the airflow patterns, the 

study demonstrated how the exbausting system becomes 

less effective as the curtain was moved further away 

from the face (Luxner, 1969). Figure 6 illustrates how 

a blowing face ventilation system can be beneficial fo r 

methane removal but detrimental for dust control, while 

the exhausting face ventilation system is advantageous for 

dust control, but disadvantageous for methane removal. 

FIGURE 8 

Airflow patterns for blowing and exhausting face ventilation systems. 

Exhausting Exhausting F.co 

! 

1' , 

,. 

: 

/.-.....

( : 

·

~ 

.... ··'·

i 

, \ 

l 

1 ~ \ •••• :: 20' 

\'., ''' ',:. ., . :.,~ /(. 

~. 

tt 

Une , 0-1.0 KEY

Botttice 

§ 

....."'",. 

10' 2' . >5

0"1<5 Blowing F",. 0<' pct

f,-~1 r~ 0-1.0 pet C) Turi:luIeoce

......... 1 
-+ Seo>nda'Y 

J ~ ~('" 20' ...­

t (::.j .--" Primary Uno airllow t tr- r

, ''\':"

,. 

J ""'-" 
 ~ ..... 

u~ 

Une ~ ~ 

""­

'0' T '0' T

Airflow patterns Methane, Pet 

F~. 

J 

'0' 

.....-' 

0-1.0 pd 


Methane 


t t 

Uno KEY a",_ 

'0' 2' . >5

0"1<5 

Face D <, pct

I C'} Turbulenca

M.O ,,' p<:t '0' 

Me1han. -+ Sea>ndwy -.J .irlIow 

Uno _.... Primary a..­ .m1ow §

, 

! ! 

'0'­ T

Methane, Pd 

I 

J ~ 10'

~ 1'1 

0-1.0 pet 


Methane 


t t I 


Lin.


-

2' '0' 

BlOwing 

I

Wt '0' -.J

UHJ

, .,
 }!::,. 

§

, 

""'''''' 

0-1.0pct 

Methane 

'0' 2' 

Ain'low patterns 
­

USBM coal mine ventilation research 

from 1970 10 1990 

The Federal Coal Mine Health and Safety Act of 

1969 had the most significant impact on face ventilation 

research. Prior face ventilation efforts were directed 

towards removing methane from the face. The new Act 

now added the burden of controlling respirable dust to 

the face ventilation systems. Mine operators now had to 

keep respirable dust below 2 mglmJ in addition to keeping methane levels below 1 percent. The use of blowing 

face ventilation, which had been recommended as the 

best method for methane removal, could result in higher 

dust levels. 

To maintain leve.ls of respirable dust and methane at 

permissible levels, new recommendations were made fo r 

face ventilation. Blowing face ventilation was acceptable 

as long as the end of the curtain was kept outby the COntinuous miner operator. However, this required a waiver 

to allow the end of the curtain to be more than 3 m (10 

ft). from the face. This practice, though, would not do any~ 

thlDg 10 reduce the dusllevels 10 the shuttle car operator 

positioned oUlby the mouth of the blowing ventilation. 

The best practice recommended an exhausting line brattice system for face ventilation with the end of the curtain 

mainlained within 3 m (10 ft) of the face. Still, with this 

system there was the disadvantage of methane buildup at 

the opposite corner to the line brattice due 10 recirculation of air and the inability of the airflow to penetrate the 

off-curtain side corner. To overcome this disadvantage, a 

diffuser fan could be mounted on a continuous miner with 

the fan's exhaust directed to the problematic corner. To 

operate this type of diffuser face ventilation system. the 

exhausting line brattice or vent tubing must be inby the 

diffuser intake, as shown in Fig. 7 (Mundell, 1977). 

FlGURI 7 

Diffuser fan with an llxhausting face ventilation system. 

Damper or Shutoff 

Mechanism 

Diffuser Fan 

Intake air 

t 

Inlake 

air Several studies were conducted to assess devices that 

would keep the (ine brattice within 3 m (10 ft) of the face. 

Some studies examined the use of extensible line curtain 

and ventilation tubing systems. The extensible line curtain, 

which was a device that allowed the line brattice curtain 

to be extended to the face without the miners having to 

go under unsupported roof, was better suited for use with 

blowing ventilation and could be used to increase face 

airflow (Thimons et ai., 1999). It failed to gain acceptance 

because il was difficult to maintain and it led to air leakage problems. Extensible tubing systems, as shown in 

Fig. 8, were extended either independently of the mining 

machine or by attaching the end of the lubing to the min~ 

ing machine. 

flGURIa 

Diffuser fan with an exhausting face venlilalion system. 

This system, while more readily accepted by 

the industry, tended to obstruct face visibility and restrict 

mobilily of the mining machine (Monaghan and Berry, 

1976; Muldoon, 1982). 

The use of auxiliary tubing that could be extended 

from an auxiliary fan without moving the fan was also 

investigated. Initially, tests were conducted with auxiliary 

fans that had no tubing attached. For a 12-m (4O-ft) setback 

distance, these free-standing fans delivered more air to 

the face than a blowing curtain (Goodman el aI., 1992). 

However, it would be difficult to use a freestanding fan 

during mining without interfering with the movement of 

equipment. 

Other studies evaluated novel devices such as air curtains and sideboard devices to improve face ventilation. 

The use of an air curtain was evaluated as an extension of 

the line brattice curtain. The air curtain consisted of a thin, 

hollow pipe with holes perforated on the topside of its 

surface. This device was located on the continuous miner. 

When connected to a small centrifugal fan, air emanated 

from the perforated surface creating a curtain of air that 

Howed from the device to the roof. This device did reduce 

respirable dust concentratio~s at .the continuous miner operator position. These reductIons In concentrations, though, 

did not justify the amount of effort to install and operate 

this system (Krisko, 1977). 

A sideboard device, which consisted of a 1.2· x 24·m (4­

x8-ft) sheet of plywood mounted on a continuous miner was 

also evaluated. This device was shown to be effective. But it 

required the use of additional water sprays that were used 

to seal the open area between the sideboard device and the 

end-of-the-line brattice. This device never became widely 
used because the extra water required for proper operation could cause floor 

problems. Additionally, there was the 

disadvantage that thesideboa: d blocked 

the operator's view of the side of the 

continuous miner on which the device 

is mounted (Divers et aI., 1979). 

Extensible brauice and tubing systems, air curtains and sideboards did not 

meet with much success because they 

were generally more difficult to implement than existing systems. Additionally, variances allowing the line curtain 

to be greater than 3 m (10 ft) from the 

face were easy to obtain as long as 

scrubbers and arrays of directed water 

sprays (spray fans) were in place (Mul

doon et at, 1982). However,subseque'nt 

research dealing with flooded-bed dust 

scrubbers did yield successful results. 

Face ventilation research continued 

on the use ofscrubbers and Oil methods 

for improving exhausting line brattice systems. During 

this time, scrubbers were becoming more prevalent, as 

they were effective in reducing respirable dust levels 

while assisting the face ventilation system to ensure that 

methane levels were acceptable. Additionally, with U.S. 

Mine Safety and Health Administration (MSHA) approval, they allowed llile brattice setback distances up 

to 6 m (20 ft). There was concern that recirculation of air 

caused by the scrubbers and auxiliary fans would lead to 

methane buildup at the face, which could potentially lead 

to expiosions.A study demonstrated that recirculation of 

air did not create methane buildup as long as fresh air was 

maintained to the face. The airflow patterns of the fresh air 

at the face were influenced through the use of a scrubber, 

but the scrubber itself did not cause methane to buildup. 

Problems only occurred when the flow from the scrubber 

exhaust interfered with fresh airflow to the face (Kissell 

and Bielicki, 1975). 

Further research was conducted to determine the best 

duct discharge configuration with the scrubber systems for 

methane dilution with an exhausting line brattice. There 

were three optimal discharge configurations for a twin 

scrubber configuration, shown in Fig. 9, with line brattice 

distances from the face varying from 1.5 t06 m (5 to 20 ft). 

:F~'~G~U~R~'~9~..,."",~~"",~"",~"",!",...._ .. ..""""",,,,,,___ • 

j

Plan and side views of a twin scrubber layoLrt on 8 continuous miner. 

c 

LEGEN D 

~,t"~;;;;i',"i ,,~g~\,:::-__jl,,';;:;[!~2:iS::1!! ~DlStharge air 

These configurations are, from lowest to highest methane 

removal efficiencies: left side perpendicular to the rib, 

right side 45° toward the face (looking towards the face); 

left side off (no flow), right side 45° toward the face; and 

left side 45° away from the face, right side 45° toward the 

face (Divers et a1., 1981). 

USSM coal mine ventilation research from 1990 

to 2006 

During the 199Os, the number of mines using remotely 

controlled continuous mining machines increased. Operating a mining machine f(:motely enabled a machine 

operator to cut to depths greater than 6 m (20 ft) without 

exposing workers to unsupported roof. Cutting depths of 

11 to 15 m (35 to 50 it) were common on many mining 

sections. With deep cutting, worker exposure to airborne 

respirable dust generally decreased as work locations 

became further removed fwm the face. However, with 

­

the deeper cuts it was more difficult to maintain curtain 

or tubing setback distances. The result was that a large 

percentage of the air delivered to the end of the curtain 

or tubing did not reach the face (Thimons et al., 1999). 

Consequently, face methane levels increased. 

Research focused on the development of improved 

face ventilation techniques for deep cutting mining sections In general, it was assumed that the amount of intake 

air supplied to a 'mining entry was sufficient to ventilate 

the face and maintain methane levels below 1 percent. 

Improvements in face ventilation would result if more of 

the available air could be delivered to the face. The follow

ing two approaches were taken in researching techniques 

for ventilating deep cuts: 

• 	 Maintain constant ventilation curtain/tubing setback 

distance (advance the curtain or tubing as the mining 

machine advanced). 

• 	 Use auxiliary means to better use available intake air 

(use fans/scrubbers to improve ventilation effectiveness). 

Earlier work showed that designs for extensible face 

ventilation· systems did not work and could not be adapted 

to a deep-cut mining sequence. However, previous work 

with water sprays and scrubbers did show that they were 

effective for dust control. And, because they moved air, 

they helped to dilute and remove methane liberated at the 

mining face (Volkwcin et at, 1985;Volkwein andThimons, 

1986). Tests evaluated how sprays and scrubbers might be 

used to improve airflow during deep cutting. 

Scrubbers are effective in removing methane and 

respirable dust from the face for blowing and exhausting 

face ventilation systems with the most effective methane 

removal occurring when using a blowing face ventilation 

system (Taylor et aJ., 1996). When using scrubbers, it is 

required tbat the airflow at the end-of-the-line curtain be 

equal to or greater than the scrubber capacity. For exhaust

ing face ventilation systems, this requirement bad no effect 

on dust capture. However, for sections using blowing face 

ventilation systems, this airflow was thought to overpower 

the scrubbers, allowing dust to bypass the scrubber inlets. 

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This resulted in a phenomenon called dust rollback. where 

excessive levels of dust move over the continuous miner 

into the mining section (Goodman e! ai., 2001?). Further 

research corrected this problem with the combmed use of 

scrubbers and water sprays. 

Again, tbere was considerable concern that usc of the 

scrubber might increase recircu!ation of air from the face, 

resulting in higher metbane levels, especially if scrubber 

capacity was larger than the amount of intake air available. Early and subsequent testing showed no increase in 

methane due to scrubber use as long as tbe quantity of 

intake air delivered to the end of the curtain or tubing 

did not decrease (Kissell and BIelicki, 1975; Taylor et ai., 

1997). Any recirculation that did occur was more than 

offset by improved dilution of methane due to increased 

airflow created by the scrubber (Taylor et ai., 1997;Taylor 

et ai., 2006). 

Water sprays, shown in Fig. 10, are most effective in 

reducing respirable dust levels. And their use can also improve dilution of methane within a couple feet of the face 

(Goodman et aI., 2000). 

FIGURI 10 

Diagram showing location of wetersprays on continuous 

miner. 

However, additional face How is 

needed to move the gas away from the face and into the 

return airfiow.Ang1ed sprays (30" angJe from perpendicular 

to face) directed towards the return side of the face were 

found to provide better methane removal than straight 

sprays (perpendicular to face) by providing this additional 

airflow (Taylor et al., 2006). Earlier work (Jayaraman, 1~) 

showed thai dust rollback in this situation could be mml

mized and face airflow maintained if a water pressure of 

approximately 690 kPa (100 psi) was maintained. 

The combined use of angled water sprays and the 

machine-mounted dust scrubber can be most effective for 

diluting and removing methane gas from the fa~. However,it was found that respirable dust concentratIons may 

not be reduced in the face area because the water sprays · 

produce increased turbulence al the face, which ~esulted 

in dust rollback (Taylor and Zimmer, 2001). This prob

lem was eliminated by adding more water sprays above, 

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below and on the sides of the Continuous miner boom. 

This configuration confines the dust cloud beneath the 

cutting boom allowing the scrubber inlets to remove the 

respirable dust. The additional sprays allow the co~bined 

use of the scrubber and water sprays of the contmuous 

miner to be effective at removing methane and respirable 

dust (Goodman et aI., 2CXX». 

Summary 

Significant progress has been made in face ventilation 

research since the beginning of the 20th century. This progress has resulted in improved worker health and safety. 

SpecificaUy, the researcb during the past century h'.'5.led to 

lower respirable dust levels and fewer methane Ignltlons at 

the face, while production levels baveincreased from 1.8 to 

2.7 t (2 to 3 st) per miner per day in [he early 20th century 

for nonmechanized mining methods to 4.5 to 8.2 [(5 to 9 

st) per miner per day in 1940 to 19S0 when conventional 

mining was prevalent. And then it improved to 12 to 13.6 

tid (13 to lSslpd) from 1960 10 1980when continuous mining displaced conventional mining as the preferred mining 

method (Energy Information Administration, 1991; US 

Department of lnterior, USGS, 1892-1921; U.S. Department of Interior, Bureau of Mines, 1932-1972). Most of 

the changes in the last century occurred following public 

demands for safer working conditions, new regulations 

requiring improved air quality and changes in mining 

methods. The following four events that occurred in tbe 

20th century had the greatest impact on the evolution of 

face ventilation systems: 

• 	 Mine disasters/explosions that resulted in the 

creation of the USBM. 

• 	 Increased productivity that resulted from 

changes in mining methods from 

nonmechanized to conventional and, finally, 

to continuous mining. 

• 	 The enactment of the Federal Coal Mine 


Health and Safety Act of 1969. 


• 	 The use of remotely operated continuous 

mining machines equipped with flooded bed 

scrubbers, which made deeper cutting possible. 

The USBM provided the vehicle for researching new 

face ventilation techniques. Before developing the science of face venlilation, early research looked at ways to 

reduce explosions by removing sources of ignitions. When 

mechanization increased mining production rates, new 

ventilation teChniques were needed to reduce methane 

concentrations. After the enactment of the Federal Coal 

Mine Health and Safety Act of 1969, ventilation systems 

had to be designed to control levels of methane and 

airborne dust, changing the recommend~d configuration 

of optimal face ventilation from a blowmg system to an 

exhausting system. Machine-mounted water spray and 

scrubber systems were designed as auxiliary ventilation 

devices for use with blowing and exhausting systems. The 

use of remotely controlled mining machines provided 

a challenge to maintaining face airfl.ow during deeper 

cutting. 

Current research shows that a general optimal face 
ventilation system may be either a blowing or an exhausting system that consists of a line brattice to guide air to 

the face. The choice of face ventilation system depends 

on whether dust control or methane control is the greater 

problem. The distance of the end-of-the-line brattice to 

the face may vary anywhere from 3 to 12 m (10 to 40 it). 

However, with these distancc:s, water spray systems and 

scrubbers mounted on the cominuous miner are essential 

to the face ventilation system to direct the air up to the 

face to dilute and remove methane and respirable dust. 

The specific details of a face ventilation system will vary 

between operations, as each mine has unique characteristics. These individual characteristics may influence the 

specific design of an optimal face ventilation system for 

that mine. 

The research at NIOSH continues to find ways to 

improve the health and safety of underground miners 

by further reducing methane and duSt levels at the face. 

Currently, the research emphasiS is on timely recognition of factors that could result in harm to workers due 

to high dust or methane concentrations. Personal dust 

monitors that continuously give the wearer data rega rding 

their dust exposure levels are being tested underground. 

Airfiow and methane monitors that will respond more 

quickly to changes in airflow and methane concentrations at the face are being investigated. Future research 

will emphasize improving techniques for monitoring 

methane, dust and airflow at the mining face. Based on 

airflow, dust and methane data obtained from NIOSH 

laboratory studies, computer-based ventilation models 

will be developed to improve face ventilation systems. 

An imponant goal of this research will be to provide 

individuaJ workers with techniques and tools forevaluating current ventilation requirements and designing new 

ve ntilation systems for future needs. (References are 

available from the authors.)