1 Copyright © 2007 by SME 

W. Reed, National Institute for Occupational Safety and Health, Pittsburgh, PA 

C. Taylor, National Institute for Occupational Safety and Health, Pittsburgh, PA 

Abstract

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 paper examines factors that had a significant influence on

mine face 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 ventilation designs and a consistent

commitment to mining health and safety. 

Introduction

Ventilation has 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 with 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 was to abandon the existing 

mine and start a new one nearby.

Ventilation in the early days of coal mining was accomplished by

means of a natural draft, created principally by a difference in the 

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 the return shaft, which allowed

for 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 the 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 burnt to death. Even though it was 

recognized in the 17th century that the buildup of this gas was the main

cause of the underground coal mine explosions, 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 or 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 hazard 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. Finally, the public outcry became loud 

enough in the United States that action was taken to form an agency 

that would 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 December 6, 1907; 239 were

killed 2 weeks later at Jacobs Creek, PA (Figures 1 & 2); 154 were

killed at Marianna, PA, November 28, 1908; and 259 were killed at 

Cherry, IL, on November 13, 1909 (Kirk, 1996). 

Figure 1. Historical summary of Jacobs Creek Mine disaster 

(Humphrey, 1960). 

As a result of these explosions and fatalities, the U.S. Bureau of

Mines (USBM) was formed on July 1, 1910. Part of the USBM mission

was to investigate mine explosions, methods of mining that could 

enhance the safety of miners and prevent accidents, and methods that

lead to the improvement of conditions under which mining operations 

were conducted (Kirk, 1996). The USBM conducted many research
2 Copyright © 2007 by SME 

Department of Health and Human Services. This brief overview of

research conducted by the Bureau of Mines until 1997 and 

subsequently by NIOSH gives a picture of how ventilation research has 

led to safer mining with fewer fatalities and injuries due to explosions 

and face ignitions. The research has been shaped by a commitment to 

make mining safer while providing ventilation techniques that 

complement current mining technology. 

“With great hopes for the success of the new USBM, Dr.

Joseph A. Holmes (the first director of the USBM) 

enthusiastically took up the problem of the high

mortality rate in U.S. mining and singled out its

reduction as being the first major accomplishment that

the USBM must achieve. Under his direction, significant

progress was made in perfecting methods for saving

lives in mine accidents and for lessening the dangers to 

which underground workers were exposed. Dr. Holmes

authored the slogan "Safety First," making it the

watchword of the USBM mission.” (Kirk, 1996).

Figure 2. Rescue workers at Darr-mine explosion, Jacobs Creek, PA.,

Dec. 19, 1907 (Humphrey, 1960).

USBM Coal Mine Ventilation Research from Inception through the 

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 of temperature 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

Bureau of Mines stated: 

“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 upon 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 USBM knew that canary birds collapsed in the

presence of 0.2 to 0.3% carbon monoxide while no

effects would be seen in members of the underground

party. It was noted that the bird was quickly revived

g 

for each miner underground and 500 cfm for each mule

or horse underground. The measurement for 

determining if this requirement is met was to be made at

the entry, crosscut, or break through nearest the face.

Individual state regulations may vary (Harrington and

Denny, 1938). 

The lack of adequate and efficient ventilation was recognized as 

the primary cause of gas ignitions in coal mines. It was believed that 

explosive gas did not accumulate in properly ventilated mines 

(Harrington and Denny, 1938). However, most of the early studies 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: 

(1) Use of non-permissible explosives or the improper use of

permissible explosives. 

(2) Improper installation, maintenance, or use of e1ectrical 

equipment. 

(3) Use of open lights, and misuse of safety lamps. 

Following the organization of the Bureau of Mines, acceptance

and use of permissible 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 Bureau

considered this one of its most fundamental research problems. The 

first approach to solving this problem was to view it as a flame study,

based upon 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 research during the 1920s 

studied the characteristics of the explosion process, such as the shock 

wave, gaseous products, types of flames involved and nature of

ejected particles through methane and coal dust explosion testing, as 

shown in Figure 3 (Fieldner, 1950). 

Figure 3. . Explosion from the Experimental Mine at the USBM 

Bruceton Laboratory. 

The danger of methane ignitions due to electrical sparks became

an issue as more and more electrically powered equipment was 

introduced into mines. Because of this danger, the use of animal 

haulage or permissible storage-battery locomotives was recommended 

in other than pure intake air and the use of booster and auxiliary fans 

was discouraged (Harrington and Denny, 1938; Forbes and Ankeny,

1929). The Bureau of Mines recommended that booster or auxiliary 

fans not be used for supplying air to working faces (Forbes and

Ankeny, 1929). Nevertheless, such fans were installed in gassy mines

regardless of the hazards involved, sometimes with disastrous 
3 Copyright © 2007 by SME 

It is ironic that fans or motors to be used underground

were required to be permissible because according to

the authors Harrington and Denny in 1938, there were no

fans or motors that were certified as permissible. 

Additionally, MSHA records show that the first instance

of a permissible fan occurs in 1947. 

Open lights were a source of ignition through the early 20th

century. The development of safety lamps in the 1800s reduced the 

danger of an 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 

classification 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 methane

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). Many explosions with 

loss of life were due to this practice. Ignitions due to open lights 

became less of a problem as permissible electrical lights became more 

prevalent and the flame safety lamp was delegated from a source of

light to a means of methane detection. 

The first guidelines for ventilation design were presented in 1929.

These guidelines included recommended airway velocities, minimum 

volumes of air for a split, and the optimum amounts of intake air that

should reach the face. It was recognized that a ventilation system 

would be adequate if the following guidelines were followed. Airway

velocities were not to exceed 1800 fpm in smooth-lined airways, 800

fpm in normal ribbed entries, and 600 fpm in main haulage airways. 

The minimum velocity was to never fall below 200 fpm. The

recommended minimum volume for a split of air was 10,000 cfm. The

amount of intake air from the shaft that should reach the face was 

recommended to be 50%, although 80 – 85 % was stated to be more

desirable and attainable through proper installation and construction of

stoppings, doors, and overcasts (Forbes and Ankeny, 1929). The

main focus of ventilation studies was on proper design of the overall 

ventilation system with emphasis on the proper construction and 

installation of stoppings, doors, and overcasts. 

USBM Coal Mine Ventilation Research from 1950 – 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 underground coal mines. After 1950, many 

recommendations for improving face ventilation were based on

controlled research experiments conducted in the laboratory and

underground. 

A curious note was made during some mine 

observations concerning the supervision of the

underground mine. It was noted that there was too

much “laxity” in supervision of the night shift and the

time periods during shift change. It was stated that this

was proven by the fact that many explosions occurred

during these times. For example, from January 9 to 

June 20, 1928 257 men were killed in six explosions

which occurred during night shift or at around shift

change (Forbes and Ankeny, 1929). 

During this time, both conventional and continuous mining

methods were used underground, with continuous mining becoming

more common. Each mining technique presented specific ventilation

requirements for methane 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 Figure 4. It stressed the importance of keeping 

future explosions; by eliminating the methane, the possibility of 

explosions was removed (Stahl and Dodge, 1956). 

There was an erroneous belief at this time that methane

should be allowed to buildup in the kerf. The premise

was that this methane would build up to levels above

the upper explosive limit (15%) for methane. Because

the methane levels were so high, there could be no

explosions. Bureau of Mines research proved this belief 

to be false. Research showed that the methane levels 

are higher at the back of the kerf, but become lower as

one proceeds from the back of the kerf towards the face.

These lower concentrations were not always higher than

the upper explosive limit for methane. This meant that

the possibility for explosion existed because a source of

ignition from the cutting bar could occur at any location

in the kerf. Therefore, it was recommended that the line

brattice be kept within 5 ft of the face in order to

properly remove the methane from the kerf (Stahl and

Dodge, 1956). 

Figure 4. Jay boom cutter used in conventional mining. 

The continuous miner machine changed coal mining. These new 

machines advanced working faces rapidly, generating coal production

tonnages never before seen. However, using a continuous miner 

resulted in the release of large volumes of methane. 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 could reduce the dangerously high methane

concentrations that resulted from continuous mining. It was known that 

ventilation, in addition to water sprays, was important for dust control 

(Fieldner, 1950). However, most studies during this time 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 face. 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 brattice systems were 

publicized by the USBM in the late 1920s. The guidelines stipulated

that the line brattice be constructed from the crosscut to within 5 – 6 ft

of the face in order 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

floor. The intake side of the line brattice should have a smaller, crosssectional 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
4 Copyright © 2007 by SME 

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. Consideration of the 

use of plastics, fiber glass, and other ceramic materials was suggested

(Fieldner, 1950).

Almost all other studies of this time period focused on face

ventilation when using continuous miners. Some early 

recommendations for improved face ventilation included the following

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

1. Line brattice is not effective to convey the proper amount of

air directly to the face of a continuous miner place.

2. The liberation of methane varies considerably from location 

to location. 

3. Using a blowing fan and tubing, as shown in Figure 5, to

force air to the face is effective for removing methane. 

However, the rib where the airflow passes must be kept wet,

or else more dust will be generated. 

Figure 5. Auxiliary fan used to provide fresh air to the face. 

4. Using an exhaust fan and tubing is effective for removing

methane from the face, provided that the tubing is kept

within 5 ft of the face. 

5. A combination of blowing and exhausting fans works 

effectively under the following conditions: 

a. The exhausting tubing should be located close to

the face and inby the blowing tubing. 

b. The blowing tubing should be located 20 ft or 

closer to the face but outby the exhaust tubing. 

c. The two fans should not be balanced in order to

allow airflow in the shuttle car entry. 

6. The fans used for face ventilation should be permissible with 

the following guidelines: 

a. Blowing fans should be installed on the intake

side. 

b. Exhausting fans should be installed on the return

side. 

c. The quantity of intake air available for face

ventilation should be larger than the capacity of

the fan. 

7. 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. 

8. Recirculation of air is not desirable. 

ventilation fans should be shutdown. 

Other studies were completed to determine the ventilation

properties of line brattice systems and ventilation tubing. These

studies evaluated the friction and shock losses for the material types

and installation methods of each type of ventilation system (Dalzell, 

1966; Peluso, 1968). 

A USBM engineer compared the cost of using

ventilation tubing with that of line brattice. He found

that the life of the ventilation tubing was 10 times longer

than the life of a brattice curtain. However, the cost of

the ventilation tubing was not 10 times greater than the

cost of the line brattice (Stahl, 1958). 

However, probably the most significant study completed during 

this time period was one that determined the airflow distribution 

patterns for both blowing and exhausting face ventilation systems 

using line brattice. Figure 6 (see Appendix) shows the airflow 

distribution patterns that have been established for blowing and

exhausting face ventilation systems. This figure shows how the

blowing face ventilation line brattice is effective for removing methane 

concentrations from the face. Additionally, the airflow patterns for the

blowing system display the secondary eddies that occur during airflow,

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 brattice must be close to the face in order to 

remove methane effectively. By displaying the airflow patterns, the

study demonstrated how the exhausting system becomes less 

effective as the curtain was moved further away from the face (Luxner,

1969). 

USBM Coal Mine Ventilation Research from 1970 – 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 2.0 mg/m3

 in addition to keeping methane levels 

below 1%. Blowing face ventilation, which had been recommended as 

the best method for methane removal, was no longer the best method 

to use because of the high dust levels it liberated. 

In order to maintain levels of respirable dust and methane at

permissible levels, new recommendations were made for 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

10 ft from the face. This practice, though, would not do anything to 

reduce the dust levels to the shuttle car operator positioned outby the

mouth of the blowing ventilation. The best practice recommended an

exhausting line brattice system for face ventilation with the end of the 

curtain maintained within 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 to recirculation of air and the inability of the airflow to

penetrate the off-curtain side corner. To overcome this disadvantage, 

a diffuser fan was 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 Figure 7 (Mundell, 

1977). 

The Federal Coal Mine Health and Safety Act of 1969

initially required a 3.0 mg/m3

 limit for respirable coal

dust, but decreased the limit to 2.0 mg/m3

 three years

after its enactment (Federal Coal Mine Health and Safety

Act of 1969). 

Several studies were conducted to assess devices that would 

keep the line brattice within 10 ft of the face. Some studies examined

the use of extensible line curtain and ventilation tubing systems. The 
5 Copyright © 2007 by SME 

difficult to maintain and it led to air leakage problems. Extensible 

tubing systems, as shown in Figure 8, were extended either 

independently of the mining machine or by attaching the end of the

tubing to the mining machine. This system, while more readily 

accepted by the industry, tended to obstruct face visibility and restrict

mobility of the mining machine (Muldoon, 1982; Monaghan and Berry,

1976). 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 40-ft setback distance, these free standing fans delivered more 

air to the face than a blowing curtain (Goodman, et al., 1992).

However, it would be difficult to use a free-standing fan during mining 

without interfering with the movement of equipment. These extensible

systems were better suited for use with blowing ventilation and could 

be used to increase face airflow (Thimons, et al., 1999). 

Figure 7. Diffuser fan with exhausting face ventilation system. 

Figure 8. Extended vent tubing for ventilating continuous miner face. 

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 flowed from the

device to the roof. This device did reduce respirable dust

consisted of a 4 ft x 8 ft sheet of plywood mounted on a continuous 

miner, was also evaluated. This device was shown to be effective, but 

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 the sideboard blocked

the operator’s view of the side of the continuous miner on which the

device is mounted (Divers, et al., 1979). 

Extensible brattice 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 10 ft

from the face were easy to obtain as long as scrubber and arrays of

directed water sprays (i.e., spray fans) were in place (Muldoon, et al., 

1982). However, subsequent research dealing with flooded-bed dust

scrubbers did yield successful results. 

Face ventilation research continued on the use of scrubbers and

on 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 line brattice setback distances up to 20 ft. There was 

concern that recirculation of air caused by the scrubbers would lead to 

methane buildup at the face, which could potentially lead to explosions. 

A study demonstrated that recirculation of air did not create methane 

build up 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 were only seen to occur when the scrubber was used and 

there was no fresh air provided 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 Figure 9,

with line brattice distances from the face varying from 5 – 20 ft. These

configurations are, from lowest to highest methane removal

efficiencies: left side perpendicular to the rib, right side 45o

 toward the

face (looking towards the face); left side off (no flow), right side 45o

toward the face; and left side 45o

 away from the face, right side 45o

toward the face (Divers, et al., 1981). 

Figure 9. Plan and side views of a twin scrubber layout on a

continuous miner. 

USBM Coal Mine Ventilation Research from 1990 – 2006 

In the 1990s the number of mines using remotely controlled 

continuous mining machines increased. Operating a mining machine

remotely enabled a machine operator to cut to depths greater than 20

ft without exposing workers to unsupported roof. Cutting depths of 35 
6 Copyright © 2007 by SME 

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 %. Improvements in face ventilation would result if more of the 

available air could be delivered to the face. Two approaches were

taken in researching techniques for ventilating deep cuts. 

1. Maintain constant ventilation curtain/tubing setback distance

(i.e., advance the curtain or tubing as the mining machine

advanced). 

2. Use auxiliary means to better utilize available intake air (i.e., 

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, helped to dilute and remove methane liberated at the

mining face (Volkwein, et al., 1985; Volkwein and Thimons, 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 both blowing and exhausting face ventilation systems 

with the most effective methane removal occurring when using a

blowing face ventilation system (Taylor, et al., 1996). For sections 

using blowing face ventilation systems with scrubbers, it is 

recommended that the airflow at the end-of-the-line curtain be equal to 

or greater than the scrubber capacity in order to prevent dust blowing 

by the scrubber inlets (Goodman, et al., 2000). Again, there was 

considerable concern that use of the scrubber might increase

recirculation of air from the face, resulting in higher methane 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 the quantity of intake air 

delivered to the end of the curtain or tubing did not decrease (Kissell 

and Bielicki, 1975; Taylor et al., 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 al., 1997; Taylor, et al., 

2006). 

Water sprays, shown in Figure 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 al., 2000).

Additional face flow is needed to move the gas away from the face and

into the return airflow. As long as the water pressure is high enough, a 

system of directed sprays (i.e. spray fan) on the body of the mining 

machine can be particularly effective in moving methane gas from the 

immediate face area. Angled sprays (30o

 angle 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) 

(Taylor, et al., 2006). 

The combined use of angled water sprays and the machinemounted dust scrubber can be most effective for diluting and removing 

methane gas from the face. However, it was found that respirable dust

concentrations may not be reduced in the face area because the water 

sprays produce increased turbulence at the face, possibly resulting in 

excessive dust levels, which may produce dust rollback (Taylor and 

Zimmer, 2001). This is a phenomenon that results in the dust

bypassing the scrubber inlets and moving over the continuous miner 

into the mining section. This problem can be eliminated by adding

more water sprays above, 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

Figure 10. Diagram showing location of water sprays on continuous 

miner. 

Summary 

Clearly, 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. Specifically the 

research over the past century has led to lower respirable dust levels 

and fewer methane ignitions at the face, while production levels have

increased from 2 – 3 tons per miner per day in the early 20th century for 

non-mechanized mining methods to 5 – 9 tons per miner per day in 

1940 – 1950 when conventional mining was prevalent, and then to 13

– 15 tons per day from 1960 – 1980 when continuous mining displaced

conventional mining as the preferred mining method (Energy 

Information Administration, 1991; U.S Department of Interior, 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 the 20th century had the greatest impact on 

the evolution of face ventilation systems: 

1. Mine disasters/explosions that resulted in the creation of the

USBM. 

2. Increased productivity that resulted from changes in mining 

methods from non-mechanized to conventional and finally to 

continuous mining. 

3. The enactment of the Federal Coal Mine Health and Safety

Act of 1969. 

4. 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

ventilation, 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 

recommended configuration of optimal face ventilation from a blowing 

system to an exhausting system. Machine-mounted water spray and 

scrubber systems were designed as auxiliary ventilation devices for 
7 Copyright © 2007 by SME 

system may be either a blowing or an exhausting system that consists 

of a line brattice to guide air to the face. The distance of the end-ofthe-line brattice to the face may vary anywhere from 10 – 40 ft. 

However, with these distances, water spray systems and scrubbers 

mounted on the continuous 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 regarding their dust exposure levels 

are being tested underground. Airflow 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 upon airflow, dust, and methane data 

obtained from NIOSH laboratory studies, computer-based ventilation 

models will be developed to improve face ventilation systems. An 

important goal of this research will be to provide individual workers with 

techniques and tools for evaluating current ventilation requirements 

and designing new ventilation systems for future needs. 

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8 Copyright © 2007 by SME 

g gpy 

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9 Copyright © 2007 by SME 

Figure 6. Airflow patterns for blowing and exhausting face ventilation systems.