1 

 

NIOSH VENTILATION RESEARCH ADDRESSING DIESEL EMISSIONS AND

OTHER AIR QUALITY ISSUES IN NONMETAL MINES

R.H. Grau III, S. B. Robertson, T.P. Mucho, F. Garcia, A.C. Smith

NIOSH

Pittsburgh, PA

ABSTRACT

Researchers working for the National Institute for

Occupational Safety and Health (NIOSH) at the Pittsburgh

Research Center are developing ways to protect the health of

miners. Part of that effort is improving the air quality in

metal/nonmetal mines by developing proper ventilation

techniques. The air quality of large opening nonmetal mines

can be greatly improved by using engineering controls of

contaminant prevention and proper ventilation techniques.

Contaminant prevention includes methods to reduce

contaminants from entering the mine air. Ventilation can be

improved with appropriate fan selection and fan operation used

in conjunction with air coursing using manmade and insitu rock

stoppings.

INTRODUCTION

The National Institute for Occupational Safety and Health

(NIOSH) conducts research into various mining health and

safety issues to improve working conditions for the U.S. miner’s

health and safety. To achieve this goal, researchers at the

NIOSH Pittsburgh Research Laboratory (PRL) are developing

methods and technologies to improve the air quality in nonmetal

mines particularly large entry mines. This effort is also directed

to increase the knowledge base concerning the ventilation

science of the mining industry. This paper discusses current

NIOSH research to improve the mine ventilation and mine air

quality, particularly for large opening mines. The paper covers

methods to estimate air quantity requirements for effective

dilution of diesel particulate emissions (DPM,) choosing

appropriate fans, air coursing methods and mine layouts

particularly for mines having entries with large cross sectional

areas. The most common type of mine with large entries are

stone mines followed by rock salt mines. Surveillance data from

the Mine Safety and Health Administration (MSHA) for the year

2000 shows that there were 162 active underground nonmetal

mines in the United States, of which, 117 were stone mines and

13 were rock salt mines.

The continuing and emerging air quality issues in

metal/nonmetal mines include silica dust, DPM, fog and face

shot fumes. The concentration of these contaminants can be

effectively reduced by utilizing preventive measures along with

proper ventilation. A growing concern by various health

agencies is the health risks associated with exposure to diesel

particulate matter (DPM). Various regulatory agencies, ACGIH

(2001), NIOSH (1988), EPA (2000), have confirmed the health

hazards of exposure to DPM. As this concern increases, the

mining community is confronted with DPM exposure limits.

MSHA recently addressed this health concern by promulgating

underground diesel regulations for coal and metal/nonmetal

mines, MSHA (2001). The law was meant to reduce the health

risks associated with DPM exposure. Regulations will force the

use of some form of ventilation improvement and/or emissions

control technology to both dilute and reduce workplace DPM

concentrations and DPM emissions from equipment. Most of

the common ventilation knowledge and techniques which are

utilized in some nonmetal mines are not readily adaptable to

large opening nonmetal mines. The large entries reduces the

ventilation resistance and permits large air quantities to flow

under extremely small mine static pressures. Mine designers

should incorporate this small pressure loss, large air quantity

relationship into their mine design plans.

CONSIDERATIONS TO IMPROVE UNDERGROUND MINE

AIR QUALITY

Various mining activities such as blasting, welding,

operating diesel engines and in some cases emissions from the

ground strata, create contaminants that enter the mine

atmosphere and need to be diluted. From these activities, a

growing concern is with the mine workers’ exposure to DPM

emitted from the diesel engines operating in the mine. The

research at NIOSH indicates that there is no single fix to reduce

DPM concentrations within the large opening mines. As will be

shown in this report, most underground mine operators will need

to substantially increase air quantity to effective dilute DPM. In

addition to the large air requirements, effective planning for the

placement of ventilation equipment and control devices, such as

fans and stoppings are necessary to effectively ventilate the

large opening mines. The mine operators will also probably

need to replace a few diesel engines that have high DPM

emissions with cleaner burning engines. Other DPM control

measures such as planning haulage routes and reducing diesel

engine idling times should also be considered. All these

measures will reduce DPM concentrations in the mine. We

assume that all mine operators will not replace all the diesel

engines operating in their mine. Under those circumstances,

the air requirements needed to dilute DPM concentrations to

comply with the proposed regulatory standards will also dilute

all other contaminants to compliance concentrations. The

ventilation and DPM control approaches need to be developed

simultaneously as an overall strategy to reduce DPM

concentrations. Although many options need to be considered

on a mine by mine basis, core ideas such as documented in the

following sections can be implemented by all underground large

opening mine operators. 

DPM AND OTHER AIR CONTAMINANT CONTROL

APPROACHES

The air contaminant control approach is to reduce as

much as feasible the contaminants from entering the mine or

from entering where miners are working. This is accomplished

by utilizing a variety of prevention techniques. Control

techniques are the first step in keeping DPM and other

contaminants in the mine air to acceptable concentrations.
 

2

Once the contaminants are liberated into the mine atmosphere,

the two remaining

Table 1. Typical Diesel-Powered Equipment Data for an Underground Stone Mine Producing 1.25 Million tons/year

Type of diesel-powered

equipment

Number of

vehicles

Total kw (hp) per

vehicle type

(Installed)

Pct of total kw and/or

hp per vehicle type

(Installed)

Total kw (hp) per

vehicle type

(Utilized)

Pct of total kw and/or

hp per vehicle type

(Utilized)

Rock Truck 5 2,136 (2,864) 39 1,301 (1,745) 34

Front End Loader 4 1,025 (1,375) 18 1,006 (1,350) 25

Drills 4 619 (830) 11 511 (685) 15

Scaler 2 261 (350) 5 261 (350) 6

Pickup 3 447 (600) 8 56 (75) 6

Mechanic Truck 2 373 (500) 7 37 (50) 5

Water Truck 1 172 (230) 3 120 (161) 4

Dozer 1 306 (410) 6 15 (20.5) 2

Powder Truck 1 101 (135) 2 20 (27) 2

ANFO Loader 1 50 (67) 1 45 (60) 1

Total 24 5,490 (7,361) 100 3,372 (4,524.5) 100

choices are to dilute the contaminants or isolate the mine

worker from the environment. Contaminant control techniques

include implementing proper blastprocedures, improving engine

maintenance, utilizing diesel exhaust filters and catalytic

converters, using low sulfur fuels, alternate fuels and fuel

additives, replacing engines and placing haulage routes in

return air. The extent or success of implementing these

techniques should be at least briefly examined by the mine

operator to determine which technique would have the most

impact on improving the air quality in the mine.

Two important DPM prevention techniques are utilizing

cleaner burning engines and planning haulage routes to keep

haul trucks in air that is moving out of the mine. Using cleaner

burning engines makes a significant improvement in DPM

emissions. As will be described later, the air quantity required

for adequate DPM dilution varies significantly between clean

and dirty burning engines. Table 1 provides a general list of the

diesel powered equipment and the corresponding horsepower

as well as the percent of actual operating time during a typical

shift for an underground limestone mine that is producing about

1.13 million metric tons (1.25 million tons) per year. As shown

in Table 1, truck haulage is the single largest source of DPM in

this underground stone mine, and probably all other stone

mines utilizing truck haulage. Thirty-four percent of the total

utilized diesel engine kW (hp) operating in this underground

stone mine comes from haulage (rock) trucks. Therefore,

reducing the trucks operating time or adjusting their haul routes

can have a major impact on the amount of DPM released into

the mine air or mine workers exposure. Besides switching to

cleaner burning engines, DPM from truck haulage can be

reduced in several ways. Converting to belt haulage in the mine

reduces underground truck haulage. However, consideration

must be given to the fact that associated with belt haulage is an

underground crusher. The situation should be evaluated, since

nuisance dust or silica dust may be introduced into the mine air

from an underground crusher as shown by Chekan et al.,

(2001). A separate ventilation split for the belt line, along with

other control techniques at the crusher, should be provided to

reduce dust exposure. 

Another important consideration to reducing DPM

concentrations in the mine air is to locate truck haulage routes

in air that has already ventilated the face. This permits fresh air

to first enter the working face and reduces DPM exposure to

workers at the face. Using this ventilation scenario, the haul

trucks should be equipped with a positive pressure filtered cabs

to protect the truck driver from DPM. Also, some mines may be

able to create alternate truck haulage routes using surface

routes to reduce underground haul roads. The combined effects

of implementing some or all of these preventive methods will

reduce DPM in the mine.

VENTILATION APPROACH

Many large opening mines rely on a combination of

natural ventilation and strategically placed auxiliary fans for

ventilation. Natural ventilation is created by differences in the

densities of air columns between the mine air and the ambient

outside air. Since these densities are temperature dependant,

natural ventilation changes frequently, both in magnitude and

direction. Therefore, natural ventilation alone is unreliable for

establishing a steady air quantity to the underground workings.

The mines that depend upon natural ventilation also have an

unreliable ventilation system. Nevertheless, in large entry

mines with drift openings, even small differences in elevation,

can cause large volume air movement and mine air exchange

although in an uncontrolled manner. In benched areas of the

mine, where conventional ventilation must overtake such large

volumetric space, natural ventilation is helpful. In these areas,

the large void may actually create an “air reserve.” Although

this air reserve can gradually be contaminated with DPM, the

natural ventilation does provide some ventilation relief during

working hours and cleans out the system during off shift times.

To effectively improve the mine air quality, ventilation

techniques throughout the entire mine ventilation system should

be considered. The system consists of combining mechanical

main mine fans, auxiliary fans, and mine layouts using devices

such as air walls to direct and control the air. Criteria for proper

fan selection, installation and operation for both main mine fans

and booster fans should be considered. Fan characteristics of

static pressure and quantity should be matched for the

operation. The use of air walls helps control the mine

ventilation flow, i.e., efficiently directing the air to where its most

needed and separates the intake and return airways.

Developing air walls includes making stoppings from man-made

materials or leaving rock intact to act as stoppings. 

Designing for the mine layout includes long-term planning

for proper air distribution. This includes methods to have air
3

Figure 1. MSHA diesel engine test data showing air

required for each engine.

sweep the active faces and also ventilate bench areas with

strategically placed auxiliary fans. Proper planning of haulage

routes and directions as well as drive through stopping locations

are also important.

ESTIMATING VENTILATION AIR REQUIREMENTS

Mine ventilationsystemsare designed according to the air

quality required to dilute contaminants to safe concentrations.

Once the required air quantity is determined, the ventilation

planner can determine the air quantity that will be required to be

moved by the fan after taking into consideration leakage and

pressure losses. The ventilation engineer can select the correct

fan for the job needed. As previously discussed, a result of the

new DPM regulations will be that the overriding ventilation

design parameter is for the dilution of DPM. In addition, even

though the total theoretical air quantity needed to dilute these

contaminates can be estimated, the actual conditions may

require a booster fan in selected locations to adequately mix the

air with the DPM at the source.

In order to determine the air required to dilute the DPM,

estimates must be made as to the DPM emitted by the diesel

engines operating in the mine. In order to do this, estimates of

the running percent of each vehicle must be made. Referring

again to Table 1, 24 different engines operate in the mine with

a total of 5,489 kW (7,361 hp). After considering the percent

operating time of each engine in the mine, the actual engine kW

(hp) running in the mine is reduced by about 39% to 3,373 kW

(4,524 hp). The percent operating time takes into account the

fact that not all the diesel engines are operating in the mine 100

percent of the time.

MSHA evaluates diesel engines and provides data for

determining the air required to dilute diesel exhaust gases and

diesel particulate matter concentrations to suggested levels

(MSHA, 2001). For each engine tested by MSHA, the approval

number, engine specifications and model number, engine rating

(horsepower and rpm) and ventilation and diesel particulate

indices are available. The result of the tests provides two

indices, a gas index and a particulate index. The diesel

particulate index is the estimated air flow needed to dilute the

weighted average DPM emitted during the MSHA test to a

concentration of 1,000 ug/m3. Starting on July 19, 2002, the

metal/nonmetal regulations will limit workers’ exposer to a DPM

concentration of 400 T C :g/m3

and a further limit on January 19,

2006 to 160T C :g/m3

. At the allowable DPM concentration of

160T C :g/m3

, the DPM index will be the more stringent

requirement and the suggested ventilation needed to achieve

those DPM concentrations are far greater than needed to dilute

diesel exhaust gasses. 

The air quantity required for a mine can be determined

using a cookbook approach. A list of engines operating in the

mine should be created in tabular form. The list should contain

important information about each vehicle such as the

equipment, and engine type (New Direct, Old Direct or Indirect

Injection), year of manufacturer, model, age, size, percent

operating time, catalytic efficiency and filter efficiency and

finally the engine emission. The suggested air quantity from

any engine nameplate should not be used as this value is for

diesel exhaust gases and it is generally lower than needed for

DPM dilution. Each specific diesel engine and its associated

parameters should be cross-referenced with the engines tested

by MSHA. The engine emission per vehicle is then documented

for each respective engine found on the MSHA list. Since many

commercially available engines have not been tested by MSHA,

it is unlikely that all engines in the mine will be found on the

MSHA list. The air requirements for those engines not tested by

MSHA are determined in one of three ways and listed in order

of preference: from the Environmental Protection Agency (EPA)

testing data (EPA, 2001), from the manufacturer, or from

estimates. The EPA has been regulating off-road vehicles since

1996 and their engine test data provides information for newer

engines. Also, the manufacturer’s specifications are generally

available for each engine type manufactured. If the air

requirements are not available from these sources, the

estimated air requirements can be calculated from specifics of

each engine such as the model, the age, the injection method

and the catalytic efficiency of DPM control devices (MSHA,

1999). Once this information is compiled, the estimated total

mine air is the sum of the engine air quantity requirements

operating in the mine. This technique assumes that all of the

mine air will be efficiently used to dilute the DPM and that the

air exiting the mine will be at the regulatory limit. Mine planners

should generally design for the lower concentration limit of 160tc

:g/m3 when planning their ventilation system even though that

concentration limit is not yet in law. Using this cook book

approach, the estimated air quantity required for the mine

represented in table 1 is 401 m

3

/s (850,000 cfm) to dilute to a

400 T C :g/m3concentration and 990 m

3

/s (2,100,000 cfm) to

dilute to a 160T C :g/m3

concentration given the current

equipment, controls etc. These air quantities may be too high

for practical mine ventilation, however, the required air quantity

is highly dependent upon the engines in use. Mine operators

can dramatically decrease air requirements by selectively

replacing some engines that have higher DPM emissions. Also,

as previously described, the extremely large volumetric size of

bench areas may reduce the actual air quantity required.

THE IMPACT OF SELECTING CLEANER BURNING

EQUIPMENT

Past studies such as Schnakenberg, 2001, Haney, 1998

and McPherson, 1982, have found it convenient to describe

ventilation air volume required in relation to diesel engine power

that are operating in the mine. Using this concept, mine

planners can quickly arrive at estimates of the air requirements

for specific mines. Figure 1 shows the air quantity requirements

from diesel engines that have been approved by MSHA. The

results shown are from non-permissible diesel engines greater

than 75 kW (100 hp). Although MSHA has tested a wide range

of diesel engine sizes, engines less than 75 kW (100 hp) are

generally uncommon in underground stone mines. Therefore,

that size group has an insignificant impact on the mine air

requirements.

The average air quantity suggested of all the diesel

engines shown in Figure 1 to achieve a DPM of less than160

:g/m3is 0.142 m

3

/s per kW (220 cfm per hp). This air quantity

is less than the air quantity calculated using the previously

described cookbook approach method for the diesel engines

used in the stone mine listed in table 1. Using that method, the

suggested air volume required was 0.183 m

3

/s per kW (285 cfm

per hp.) More air quantity is needed in this latter calculation

because it is a more accurate account of the operating diesel

engines in the mine and it takes into consideration that many of
4

Figure 2. Fan Curves of Axivane and Propeller Fan.

Table 2. Ventilation data for a typical underground coal and stone mine.

Mine type

Friction

factor, K (x10-

1 0)

Airway

perimeter, O, m

(ft)

Entry length, L

m (ft)

Air quantity, Q

m

3

/s (cfm)

Cross-sectional

area, A

m

2

(ft2

)

Pressure loss, H

Pa (in w.g.)

Coal 70 15.2 (50) 1,524 (5,000) 11.8 (25,000) 9.3 (100) 52.3 (0.2103)

Stone 70 42.7 (140) 1,524 (5,000) 42.7 (100,000) 38.1 (1,125) 1.64 (0.0066)

the engines are not new and are not MSHA approved engines.

Not only are engines of an older vintage less efficient, as

engines age, the combustion process degrades. This lowers

the fuel economy and promotes higher DPM emissions. This

significant difference defines why additional research is needed

to define more accurate estimates of engine emissions during

a normal duty cycle in an underground stone mine.

The MSHA data in Figure 1 shows there is a wide range

of air required for nearly identical engine horsepower. This

highlights the importance of choosing equipment with clean

burning engines. The air quantity required to dilute the DPM

from cleaner burning engines is significantly less than that

required for the dirty burning engines. From the MSHA test data

in Figure 1, the range of difference in required air volumes to

dilute the DPM emission between dirty and clean engines is

about 9.0 m

3

/s to 142 m

3

/s (21,000 to 90,000 cfm) per engine.

The engines approved in Part 7 emit fairly low DPM relative to

many EPA approved engines. Unlike coal mines, stone mines

were not required to use Part 7 engines and as a result many of

the engines they use emit more DPM and have not been tested

by MSHA. Considering the mine described in table 1, if all 24

engines were in the higher range of emissions in Fig. 1, the total

mine air quantity required to dilute the DPM emissions would be

much higher than if cleaner burning engines were used.

FAN SELECTION

Mine fans utilized in underground stone mines are usually

of the axial vane type although centrifugal and propeller fans are

occasionally used. The three fan types are each designed for

specific applications and the proper fan selection depends upon

the ventilation application. Namely, the fan needs to overcome

the mine static air pressure from resistance and develop the

required air quantity. Many underground limestone stone mines

are drift mines developed from quarry operations. Typically,

these room and pillar mines feature entries that are 6.1 m (20

feet) or higher and at least 12.2 m (40 feet) wide. These

dimensions are significantly larger than the typical coal mine in

the United States where the average dimensions are 1.5 m(5 ft)

high by 6.1 m (20 ft) wide. The large dimensions in stone mines

contribute to a low static head loss while moving large air

quantities through the entries. The static head pressure loss

can be expressed in the common pressure-loss formula for

mine ventilation which is:

where: H = pressure loss, Pa (in of H

2O w.g.)

K = friction factor for air of standard density

O = perimeter of the airway, m (ft)

L = entry length, m (ft)

Q = air quantity, m

3

/sec (cfm)

A = entry cross-sectional area, m

2

(ft2)

Therefore, in calculation, the static head loss is based

upon the reciprocal of the cube of the entry cross-sectional

area. As shown in Table 2, the typical pressure loss through

large entries such as underground stone mines is considerably

lower than what would be encountered in a coal mine. The fan

static pressure required to move 47 m

3

/s (100,000 cfm) through

one typical underground stone mine entry is about 1.64 Pa

(0.0066 in) of water gauge versus 52.3 Pa (0.2103 in) of water

gauge (32 times that of a stone mine) required to move 47 m

3

/s

(100,000 cfm) through four typical parallel coal mine entries.

Fan static pressure readings from four underground limestone

mines were taken and the results are shown in table 3. All fan

static pressure readings were extremely small unless a shaft or

slope were present. This small difference in static pressure

should be considered during fan selection for mines of this type

with large cross-sectional airways. In most cases, large

opening room and pillar mines with drift openings exhibit static

pressure losses significantly less than 248.8 Pa (1 in) w.g.

Axial vane fans are the most widely used fan type we

have encountered in underground large opening stone mines.

Axial vane fans have the capability to develop higher pressure

than that created by propeller fans. Propeller fans are designed

for a smaller range and lower potential for static head but have

more potential for higher air volumes than an axivane fan.

Although numerous fan designs are available for both fan types,

Figure 2 shows a fan pressure-quantity curve for two typical

axial vane fans and one typical propeller fan. With the current

diesel particulate concerns, large entry nonmetal mines

particularly drift portal stone mines will need large air volumes

that can be delivered at very small static pressure losses. To

date, only three underground stone mines that are using large

propeller fans have been identified. However, due to the low

static pressure and high air volume requirements, other

underground stone drift mines could benefit from their use.

Also, mines with air shafts less than 30.5 m (100 ft) in length

and at least 3.6 m (12 ft) in diameter may also benefit from

propeller fans. In those cases, if large diameter propeller fans

are used, larger diameter shafts will be needed. Figure 3 shows

the relationship between static pressure loss and shaft

diameters of 2.4 m to 6.1 m (8 ft to 20 ft) at air quantities of 165

m

3

/s (350,000 cfm.) The static pressure losses ranges from 2.8

kPa (11.4 in w.g.) for a 2.4-m (8-ft) diameter shaft to 28.9 Pa

(0.12 in w.g.) for a 6.1-m (20-ft)-diameter shaft. The pressure

loss through a shaft or a slope in large opening mines dictates

the fan selection. Corresponding to this information, a large

opening mine with drift openings or a with large shaft 6.1 m (20

ft) or more in diameter, can possibly use a high air volume-low

pressure propeller type fan. However, a mine that has a smaller

diameter shaft would have to use a higher pressure axivane fan

delivering a lower air quantity.
5

Figure 3.Static pressure loss through various size shafts at

165 m3/s (350,000 cfm).

From Table 3, Mine C is an example of a lower volume,

higher pressure axivane fan being used in a 4.0-m (13-ft)

diameter air shaft. This particular mine needed significantly

higher air volumes to dilute DPM concentrations. One option

would be to increase the air quantity by adding a second fan in

parallel. However, using two conventional high pressure axial

vane fans in parallel to increase the air quantity in a low

resistance applicationis not practical when compared to a large,

high flow/low pressure propeller fan. Two large axial vane fans

would require a high initial capital and operating cost, and the

fans would operate inefficiently at of very low static pressure.

A propeller fan may be a better choice in this application. For

planning purposes, if stone mines are to utilize the low

pressure/high volume fan concept, they must have air shafts

large enough to reduce head loss. The development cost of a

large diameter shaft generally overrides the fan choice.

However, shaft development costs for a large diameter shaft in

a stone mine will be lower than mines that require a smooth

lined air shaft to reduce friction. Realizing those cost

reductions, the reduced savings in both the capital and

operating costs of a large diameter fan should be considered.

AIR COURSING

Air flows through a mine due to differential static pressure

between locations. The air flow is always in the direction from

a higher to a lower pressure, disregarding pressure differences

due to elevation. The pressure is developed from either natural

ventilation or from mechanical fan pressure. Natural ventilation

pressure is created by differences in the air density of air

columns because of the combination of elevation changes and

temperature differences between the surface and inside the

mine. Unfortunately, natural ventilation pressure and the

subsequent natural ventilation are unreliable. The airflow may

change daily, and it is often in the direction opposite of that

desired. However, natural ventilation does offer someexchange

of mine air with outside air, albeit in a very uncontrolled manner.

A much more practical and efficient method is to ventilate using

mechanical fans to develop a pressure difference throughout

the mine. In conjunction with the fans, an integral part of the

ventilation system is to distribute mine air using stoppings

between high and low pressure airways. This concept is used

in virtually all types of mechanically ventilated mines. The

unique characteristic of underground stone mines is their large

cross-sectional area which allows the mines to be ventilated

with high air quantities at low static pressures. Although this

small pressure difference is a benefit to minimizing air leakage

between intake and returns, many mines avoid the use of

stoppings due to the cost and the problems of constructing and

maintaining a stopping in a large entry. Instead, these mines

rely on auxiliary fans that are positioned by trial and error at

strategic locations. Although very small mines may stay in

compliance with a few strategically placed jet fans, as the

physical size of the mine increases, moving adequate quantities

of air throughout the mine becomes more difficult.

CONSTRUCTED STOPPINGS

NIOSH scientists are evaluating the use of stoppings in

large opening mines. A variety of materials have been used for

stopping construction in large opening mines. Steel sheeting,

cementious-covered fiber, mine brattice, used mine belting and

piled waste stone have all been used with varying degrees of

success. Unfortunately, expense, construction, and

maintenance problems have been barriers to stoppings gaining

wide acceptance by the stone mining industry, particularly in

larger more established mines. Two stopping design criteria

are: to prevent leakage and the capability to withstand the

pressure from face production shots and the static pressures

created by the fans. Some mines have had success in

developing stoppings designed to provide relief during face

productionshots. Techniques such as leaving the brattice loose

at the floor, using VELCRO strips, or using a combination of

used mine belt and brattice have been effective. 

INSITU ROCK STOPPINGS

Rock stoppings that connect pillars can be strategically

oriented to direct the ventilation air. These rock stoppings are

created by eliminating at least the last face shots that would

normally break through two adjoining entries, thus keeping a

natural connection between two pillars. In order to direct the

air, the rock stoppings are oriented parallel to the ventilation

flow. Rock stoppings can later be mined through for optimum

stone recovery and bench mining can proceed if desired. The

long unbroken rib (air wall) utilizing stone stoppings are an

effective and practical method to direct ventilation air. This

technique reduces maintenance and the expense of building

stoppings. Stone production may be temporarily compromised

because the stone in the rock stopping is not immediately

mined. However the stone can eventually be mined when the

stoppings are no longer needed or when a new air wall is

constructed past the original stopping line. 

Table 3. Measured air quantities and static pressure through underground stone mines

Mine Airway length,

m (ft)

Shaft length,

m (ft)

Shaft diameter,

m (ft)

Slope length,

m (ft)

Slope cross

sectional area,

m

2

(ft2)

Air quantity

m

3

/s(cfm)

Fan static

pressure, Pa (in

w.g.)

A 731 (2,400) None None None None 165 (350,000) 29.9 (0.12)

B 2,134 (7,000) None None None None 132 (280,000) 14.9 (0.06)

C 1,463 (4,800) 23 (75) 4.0 (13) None None 59 (125,000) 59.7 (0.24)

D 464 (5,000) 14 (150) 3.0 (10) 244 (800) 14 (156) 130 (275,000) 671.8 (2.7)
6

Figure 4 Perimeter Ventilation.

Figure 5. Unit ventilation.

MINE LAYOUTS USING VENTILATION IDEAS

The concept of incorporating mine planning and

ventilation ideas together is an important step in improving the

ventilation in the mine. By strategically planning stopping and

auxiliary fan locations, stopping types, and truck haulage

routes, the mine ventilation efficiency and air quality will be

improved. By increasing the mine ventilation efficiency, the air

quantity needed from the fan is reduced because a higher

percentage of air reaches the face sections. A mine ventilation

system that has high efficiency means less leakage and less

recirculation. Also, by increasing the efficiency, the air

exchange rate in the mine is also increased. In any case, mine

operators should strive for fresh, uncontaminated intake air to

the working faces. To help accomplish this goal, truck haulage

should be primarily routed in air that has already ventilated the

working faces (return). Haulage trucks are the major single

source of DPM. Keeping truck haulage from entering the

working face sections is an important concept to prevent

excessive DPM concentrations at one location of the mine.

Although planning of haulage routes reduces mining flexibility,

the benefit received in reduced DPM concentrations should

outweigh the reduced flexibility. 

The concept of increasing the air exchange rate to mining

activities is also important. On a typical working day, the first

shift follows several hours of down time proceeding the

completion of the night shift. If the mine air turns over before

the workers on the new shift arrive, they will enter the mine in

fresh uncontaminated air. Also if the exchange rate is quick

enough, some air can be recirculated in a controlled manner

from the bench areas to the development areas. 

Considering the above criteria, NIOSH researchers have

identifiedthree different ventilationconcepts for ventilatinglarge

underground stone mines: perimeter ventilation, unit ventilation

and split mine ventilation. Real working experiences are

needed to verify the successfulness of each concept. We have

observed mines incorporating at least some parts of these

concepts in daily practice, however no real data exists as to the

successfulness of the methods. 

The goal of all three concepts is to supply fresh

uncontaminated air to the faces. Each method is defined by a

unique mining layout that is advantageous for different mine

applications. To properly choose the correct ventilation plan,

the size and extent of the mine should be considered. All the

methods utilize a main mine fan to move the air, and they all

utilize air walls to direct and course the air. In most cases, jet

auxiliary will be required to address the ventilation needs for

localized areas where diesel equipment concentrated. Auxiliary

ventilation fans should be positioned to work in conjunction with

main mine fans and not directed in an opposing direction.

During the planning process, considerations need to be

given as to the choosing between a blowing or exhaust system.

Either method is capable of diluting contaminants in the mine

and each method has it’s pros and cons. One advantage of a

blowing system is the elimination of the need for check curtains

on the truck haulage routes as the trucks leave the mine. Other

considerations are the circumstances that develop when the

intake air enters the mine. Air entering on slope declines may

creates hazardous conditions with icy roadways during the

winter season. Also, shaft air intakes may have considerable

condensation present during the summer months. This could

promote ground control problems near the shaft. These criteria

should be fully considered for all three ventilation methods. 

PERIMETER VENTILATION

The perimeter ventilation system is particularlyapplicable

to existing large mines. The perimeter ventilation system is

designed to keep the active faces, or the outside perimeter of

the mine, always under intake air as shown in figure 4. This is

accomplished by separating the developing active mining areas

from the rest of the mine by an air wall. Ventilation is provided

to the area by utilizing a bulkheaded main mine fan. Since the

mining front continually expands, a second air wall is developed

at least four entries beyond and parallel to the first air wall. In

an older developed mine, the first air wall needs to be

developed by creating stoppings. However, the second air wall

could be developed using insitu stone. A check curtain every

third or fourth crosscut through the air wall allows for equipment

haulage. As mining progresses beyond the second air wall, and

a third air wall is developed, the second air wall can be mined

through and the stone recovered. By alternating in this manner,

the working faces will always remain in adequate ventilation. In

many of large mines, extensive benching areas will be already

developed, these areas can normally be ventilated by the

combination of natural ventilation and auxiliary fans.

UNIT VENTILATION

Figure 5 describes the unit ventilation method in which a

series of “units” or “sections” are created which are the active

mining areas. The unit ventilation plan is applicable to newer

mines especially if air shafts are present. The units described

in this method are a planned mining block of significant size

(several pillars) that contain the working faces and that is

surrounded on four sides by long air walls incorporating stone

stoppings. The air walls have only a few openings or check

curtains which allow for ventilation control and haulage. One

advantage of this method is that it allows for these units to be

at least partially removed from the main mine ventilation circuit

when mining development is completed. The method is also

less dependent upon one mining front which can be a problem

if poor roof conditions are encountered. In the unit ventilation

method it may be possible for one auxiliary fan to provide the

ventilation for that separated section. The size and capacity of

the fan will be dictated by the section size.
7

Figure 6. Split mine ventilation.

SPLIT MINE

Split mine ventilation, shown in figure 6, is designed to

split the mine into two parcels, intake and return, separated by

an air wall. The face ventilation using this system is similar to

the perimeter ventilation method in that air is coursed by air

walls. However the system uses a air wall that is built as a

permanent structure. Like the unit ventilation, the split mine

ventilation is particularly good for newer mines. The method is

also effective for utilizing truck haulage in return air and for a

developing mine with drift openings. Like the other ventilation

methods, this system keeps the working faces in fresh air. 

CONCLUSIONS

NIOSH is researching various ways to improve ventilation

in large opening mines and is currently focusing on contaminant

prevention, fan applications, air coursing and implementing

mine ventilation techniques into the mine layout. Prevention

techniques include implementing proper blast procedures,

improving engine maintenance, using exhaust filters, higher

quality low sulfur fuels, fuel additives and locating truck haulage

routes in return air. 

Two very important prevention techniques are utilizing

cleaner burning engines and better planning of haulage routes

to reduce haul time in the mine. Truck haulage is the single

largest source of diesel particulate in an underground stone

mine. Mine operators can dramatically decrease air

requirements by selectively replacing engines or adding control

measures to engines that emit the most DPM. Ventilation

techniques which can be used in underground stone mines are

the proper use of mechanical fans, and developing air walls and

mine layouts incorporating ventilation concepts. Underground

stone mines are large opening mines that feature a small head

loss for ventilation air. Propeller fans should be suited to

produce large air quantities under low static head loss

conditions. The use of stone stoppings is being researched

particularly as to how they can be implemented in the mine

layout. Three mine layouts incorporating ventilation have been

identified: perimeter ventilation, unit mine ventilation, and split

mine ventilation. All three methods keep the working face in

fresh air. Operators of all underground stone mines should find

that these recommendations will improve their ventilation in the

underground workings.

REFERENCES

American Conference of Governmental Industrial Hygienists

(ACGIH), 2001, “Threshold Limit Values for Chemical

Substances andPhysicalAgentsand BiologicalExposure

Indices."

Chekan, G. J., Colinet, J. F., Grau III, R. H., 2001, “Silica Dust

Sources in Underground Metal/Nonmetal Mines - Two

Case Studies,” In publication for 2002 SME Annual

Meeting, Phoenix AZ.

Haney, R., Saseen, G., 1998, “Estimation of diesel particulate

concentrations in underground mines,”Preprint 98-146 for

presentation at the SME-AIME Annual Meeting Orlando,

FL, March 9-11,.

McPherson, M. J., 1982, “The EnvironmentalAspects of Diesels

in Underground Mines,” IM & EJ, April.

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

Department of Labor, 2001, “MSHA Web Site,

Nonpermissible diesel engines approved under Part 7",

http://www.msha.gov/S&HINFO/DESLREG/1909a.HTM

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

Department of Labor, 2001, “Final Rule 30 CFR Part 57,"

January.

National Institute for Occupational Safety and Health (NIOSH),

Department of Health and Human Services, 1988,

“Carcinogenic Effects of Exposure to Diesel Exhaust,”

Publication 88-116, 30 pp.

U.S. Environmental Protection Agency (EPA), 2000, “Health

Assessment Document for Diesel Exhaust,” Report

EPA/600/8-90/057E, July.

U.S. Environmental Protection Agency (EPA),

http://www.epa.gov/otaq/certdata.htm#largeng

Schnakenberg, Jr., G. H., 2001, "Estimate of Technically

Feasible Dpm Levels for Underground Metal and

Nonmetal Mines," Mining Engineering, Sept.