The effects of ventilation controls and environmental cabs on 

diesel particulate matter concentrations in some limestone mines 

J. D. Noll, L. Patts, & R. Grau 

National Institute for Occupational Safety and Health, Pittsburgh Research Laboratory, Pittsburgh, PA 

ABSTRACT: MSHA has promulgated a rule to limit the exposure of underground metal/nonmetal miners to 

diesel particulate matter (DPM). In May 2008, the final personal exposure limit will be lowered to 160 μg/m3

 total 

carbon. To comply with this rule, mine operators are implementing a variety of control technologies. In this study 

two types of control technologies (ventilation and cabs) which are being implemented in limestone mines were 

investigated. Two stone mines in this study use large diameter propeller fans for main mine ventilation and direct 

the air to the faces using auxiliary fans, stoppings, and long pillars while bypassing the old mine workings. 

NIOSH measured for sub-micrometer elemental carbon (EC) using SKC DPM cassettes (analyzed using NIOSH 

5040) and a near real time instrument. With the present ventilation and the number and type of vehicles used, the 

concentration of EC from DPM at the working areas was at or below 400 μg/m3

 for both mines and about 166 

μg/m3 and 251 μg/m3 at the returns. The real time data showed that the ventilation was reaching the working areas 

and effectively diluting the DPM. Environmental cabs were also used to reduce DPM exposures in three 

underground limestone mines. Using NIOSH method 5040 and near real time EC instrumentation, NIOSH 

sampled inside and outside of a loader cab at one of these limestone mines to determine the effectiveness of the 

cab. The cab was found to be over 90% effective in removing DPM as long as the cab system was properly 

maintained, and doors and windows were closed. 

1 Introduction 

Long-term exposure to elevated concentrations of diesel 

exhaust is a concern, because diesel particulate matter 

(DPM) is believed to be a possible carcinogen. 1-3 

Exposure to elevated concentrations of diesel exhaust has 

also been linked to health effects such as eye and nose 

irritation, headaches, nausea, and asthma. 4-6 Because 

underground miners are exposed to some of the highest 

levels of diesel exhaust in the United States, the Mine 

Safety and Health Administration (MSHA) has 

promulgated rules to limit the exposure of metal/nonmetal 

underground miners to DPM. MSHA uses total carbon 

(TC) or elemental carbon (EC) as a surrogate because 

DPM could not be measured directly. The personal 

exposure limit is 350 μg/m3 total carbon (269 μg/m3 

elemental carbon) for the 2007 interim limit and 160 μg/m3 

total carbon for a final limit effective in 2008.7-8 

In order to comply with this rule, mines are 

implementing a variety of controls to reduce DPM 

concentrations. Some such controls are alternative fuels 

such as biodiesel, diesel particulate filters, ventilation, 

emission based maintenance, newer engines, 

environmental cabs, and some administrative controls. 

Mines are experiencing a variety of results when trying 

these different DPM reduction strategies. NIOSH is 

currently surveying a variety of metal/ nonmetal mines to 

document what methodologies mines are using to reduce 

the DPM. The compiled information may help the mining 

community reduce DPM exposure of the underground 

miners. 

This paper concentrates on surveys conducted at two 

stone mines that were using ventilation and enclosed cabs 

to reduce DPM exposure. Two stone mines instituted a 

combination of unit and perimeter ventilation system and 

large diameter propeller fans to reduce contaminant

concentrations.9-10 Both mines were able to direct a

substantial airflow to the face using long pillars or 

brattices. NIOSH measured the ventilation and DPM

concentrations in several areas of these mines to determine 

the concentrations of DPM that were being achieved due to 

the combination of ventilation under existing operating 

conditions. 

These stone mines also used enclosed cabs to reduce 

DPM exposure. Cabs have been shown to be very effective 

(over 90%) in removing different contaminants when 

properly working.11-13 Cabs have also been reported to leak 

without proper maintenance and can provide different 

effectiveness depending upon factors such as type of 

contaminant, pressurization, cleanliness of cab, etc.11-13 It

is important, therefore, to investigate how these enclosed 

cab systems on working mining vehicles remove DPM. In 

order to determine how effective cabs in some mines can 

be, NIOSH investigated the effectiveness of an enclosed 

cab on a loader in reducing DPM. NIOSH conducted this 

investigation at a third limestone mine. 

2 Methods 

2.1 Mine Survey 

In several underground stone mines, ventilation and 

environmental cabs are used as a strategy to lower DPM 
 

 

 

 

 

 

 

 

 

exposure. NIOSH evaluated these strategies in three 

underground stone mines to document the successes and 

failures for information to the mining community. NIOSH 

measured the ventilation and noted the type of ventilation 

used in two stone mines. DPM measurements were made 

in several areas of the mines to determine what 

concentrations of DPM were achieved with this mine’s 

ventilation package. NIOSH also investigated the 

effectiveness of an enclosed cab in a third limestone mine. 

2.1.1 Ventilation 

A vane anemometer was used to obtain ventilation 

measurements. Measurements were taken in several areas 

of the mine (return and some locations near the face). The 

anemometer was attached to an extendable rod and one 

minute entry cross sectional measurements were taken. 

2.1.2 Area Samples 

Area samples were taken at several locations in two stone 

mines to determine the DPM concentrations in these mines 

as well as the effects of the current ventilation systems. 

The EC monitor and three SKC DPM cassettes (standard 

setup method for EC and TC) were located in a basket on a 

tripod (see Figure 1), and were operated for six hours of a 

shift during a production shift of an underground stone 

mine. 

Figure 1: Apparatus for area sampling which includes an 

EC monitor for real time analysis, SKC DPM cassettes for 

NIOSH 5040 analysis. 

A basket was setup at the intake of the mine (fresh air 

brought into the mine), the return (the exit of the intake air 

after passing through the whole mine), and at several 

locations at the working area where loaders were loading 

the limestone into haul trucks. Drilling, roof bolting, and 

scaling were also performed at the working areas. The EC 

monitors were downloaded each day and the EC 

concentration was calculated using a calibration curve. 

The EC monitor is a near real time instrument that 

measures elemental carbon in 5-15 minute averages 

depending upon concentration. The instrument is described 

in other publications.15-16 

The quartz filters from the SKC DPM cassettes were 

analyzed for EC at the NIOSH Pittsburgh Research 

Laboratory using NIOSH 5040.14 Area samples were taken 

in the mine for three days. 

2.2 Enclosed Cab 

These and other stone mines also use enclosed air 

conditioned cabs to reduce the miners’ exposure to DPM. 

These cabs are air conditioned and filter (both a course 

filter and hepa filter are used) out the DPM to provide a 

cleaner atmosphere for the miner. In order to evaluate the 

efficiency of a cab to reduce DPM, two baskets each 

containing an EC monitor and three SKC DPM cassettes 

were prepared. One of the baskets was then strapped onto a 

loader (a Caterpillar 980F) outside the cab in Mine C. 

Another identical basket was placed inside the cab of the 

vehicle where the miner operates the vehicle. The loader 

was used to clean up areas in the mine and was run during 

normal production for this stone mine. After about 6 hours 

of sampling, the samples were removed from the vehicle. 

This sampling procedure was continued for five days at a 

stone mine. 

The quartz filters from the SKC DPM cassettes were 

analyzed for EC at the NIOSH Pittsburgh Research 

Laboratory using NIOSH 5040.14 The EC monitors were 

downloaded each day and the EC concentration was 

calculated using a calibration curve. 

The reduction efficiency (the effectiveness of the cab 

to remove DPM) was calculated using the EC values from 

the NIOSH 5040 analysis using the following equation: 

(ECoutside − ECinside) Re duction efficiency ≡ x100 

ECoutside 

ECoutside – The EC concentration measured by NIOSH 

5040 outside of the cab. 

ECinside – The EC concentration measured by NIOSH
 

5040 inside of the cab. 

3 Results and Discussion 

3.1 Ventilation 

3.1.1 Mine A 

Table 1 shows the ventilation measured at mines A and B. 

Mine A used a perimeter ventilation method as shown in 

Figure 2. The ventilation system consisted of two 

exhausting propeller fans and brattice curtain stoppings to 

course the ventilation air across the active faces while 

bypassing the bulk of the old mine workings. An auxiliary 

fan was placed in the fresh air stream to draw air to the 

faces. Airflow of 310 m3

/s (660,000 cfm) (D) was 

measured to be exhausting from the two main mine 

propeller fans. Additional air measurements were taken 

365-m (1,200 ft) from the main mine fans and totaled 270 

m3

/s (570,000 cfm) (A-C). Since a brattice curtain line 

was used, face distances further from the fan would have 
 

 

 

 

decreased the available airflow. Previous tests9-10 found 

about 33% of total airflow was available 975-m (3,200-ft) 

from the face at this mine. 

Figure 2: Ventilation and diesel particulate matter 

sampling points for Mine A. 

Table 1: Ventilation Results 

Mine Location Ventilation (cfm) 

Mine A Return Portal 660,000 

Mine A Main Entry C 326,000 

Mine A Main Entry B 129,000 

Mine A Main Entry A 114,000 

Mine B Total Exhaust 554,000 

Mine B Location A 316,000 

Mine B Location B 209,000 

3.1.2 Mine B 

A notable difference in this mine from Mine A was that the 

main airflow was coursed and directed by a series of long 

stone pillars which separate the intake airways from the 

return airways. The mine was also phasing into unit 

mining. Research by NIOSH has shown that the use of 

long stone pillars instead of brattice curtain will maintain 

the total ventilation efficiency over a longer distance.10 

Long stone pillars eliminate the construction and 

maintenance costs associated with brattice curtain 

stoppings. Long stone pillars also eliminate leakage, 

resulting in both an increase in total mine, and delivery 

ventilation efficiencies. Using long stone pillars can be a 

key factor in maintaining adequate ventilation airflows at 

increasing distances from the fan to the active production 

faces where ventilation is most critical. The unit ventilation 

method is based upon a preexisting airflow system to block 

off an area for development. Units of pillars are created 

that are surrounded by in-place stone stoppings. 

Figure 3: Ventilation and diesel particulate matter 

sampling points for Mine B 

Mine B had a long pillar line with six cross cuts along 

the 850-m (2,800 ft) of length. The crosscuts nearest the 

fan have been sealed with piled stone and brattices 

although leakage has not been completely eliminated. Of 

the 280 m3

/s (590,000 cfm) entering the mine, about 250 

m3

/s (525,000 cfm) (A, B) ventilated the working sections 

and was measured passing through the last two openings in 

the stone pillar as seen in Figure 3. This air ventilated the 

unit mining section and subsequently was sampled for 

DPM. 

In both mines, good ventilation was reaching the face 

indicated by the air flow after passing through the face 

areas. A substantial part of the airflow was still measured 

even after passing through the face area (locations A-C in 

mine A and locations A-B in mine B). 

3.2 Vehicles Used in The Mine 

Mining equipment utilizing both new and old engines was 

used in both mines A and B. Over 12 vehicles were 

working in the mines at one time (loaders, haul trucks, 

drillers, scaler, water truck, etc.). 

3.3 DPM Concentrations 

Diesel particulate matter (DPM) could not be measured 
 

 

 

directly due to sensitivity of the method (gravimetric) and 

interferences (mineral dust, cigarette smoke, etc.). Total 

carbon was susceptable to potential interferences (cigarette 

smoke, vapor phase OC, etc.) Therefore, elemental carbon 

(EC) was used as a surrogate to measure DPM since 

elemental carbon is not prone to interferences. It is also 

used by MSHA to determine total carbon concentrations 

for the interim PEL,8 and in a previous study, EC was 

shown to have a linear relationship between DPM and TC 

from DPM in several metal/nonmetal mines.17 

Elemental carbon (EC) results measured via NIOSH 

5040 are shown in Table 2. The results show the average 

concentration for about 6 hours of sampling per day for 

three days. EC concentration can vary from day to day 

depending upon the number of vehicles operated and 

production levels. Three days of sampling were performed 

to permit averaging of some of the fluctuations caused by 

daily production changes. 

Table 2: NIOSH 5040 Results 

Mine Location EC (g/m3) 

Mine A Intake* 10 

Mine A Return* 251 

Mine A Face 1 * 180 

Mine A Face 2 * 216 

Mine B Intake* 4 

Mine B Return* 166 

Mine B Face 1A 94 

Mine B Face 1Bt 198 

Mine B Face 2A 91 

Mine B Face 2Bt 171 

*average of three days

t

 average of two days 

 

 

As seen in Table 2, the NIOSH 5040 results show that 

in Mine A, the average EC concentrations were about 251 

μg/m3

 at the return and in Mine B the average EC 

concentration was about 166 μg/m3

 at the return. 

The NIOSH 5040 results derived from the area samples 

obtained in Mine A and B do not provide a good 

evaluation of the DPM concentration at the working area 

because the vehicles were only working in the area where 

the samples were collected for part of the day. The near 

real time EC data from the EC monitors collected during 

the time the vehicles were operating would more closely 

represent the DPM concentrations expected at a working 

face than do the NIOSH 5040 results. 

Figures 4 and 5 are examples of near real time data at 

the working areas. As can be seen by Figure 4, for this 

working area in Mine A, the miners were not working 

directly at the face where these samplers were until 13:00. 

The concentration of EC before the vehicles were 

operating at this face was about 200 μg/m3

. The 

concentration increased to about 400 μg/m3

 with an 

average of about 350 μg/m3

 when the vehicles were 

operating near the samplers. One would then expect the 

concentrations of EC to be around 350 μg/m3

 where some 

of the miners are working in Mine A. 

 

450.00 

400.00 

350.00 

EC (ug/m3) 5 min avg 300.00 

250.00 

200.00 

150.00 

100.00 

50.00 

0.00 

8:24 9:36 10:48 12:00 13:12 14:24 15:36 

Time 

Figure 4: Near real time EC concentration for area samples 

at the working area of mine A. This showed the highest 

concentration achieved in the three days of sampling. 

400.00 

350.00 

300.00 

EC (ug/m3) 15 min avg 250.00 

200.00 

150.00 

100.00 

50.00 

0.00 

8:24 9:36 10:48 12:00 13:12 14:24 15:36 

Time 

Figure 5: Near real time EC concentration for area samples 

at the working area of mine B. This showed the highest 

concentration achieved in the three days of sampling. 

After examining the near real time data for all of the 

days and areas sampled, the highest concentration seen in 

Mine A was about 400 μg/m3

 and 350 μg/m3 for mine B at 

the face. The highest average concentration when the 

vehicles were working in the area of the samplers was 

about 350 μg/m3

 for mine A and about 250 μg/m3 for mine 

B. 

Mine A was achieving EC concentrations around 251 

μg/m3

 in the return and at or below 400 μg/m3 at the 

working area with the ventilation package and number and 

type of vehicles used. Mine B was achieving EC 

concentrations around 166 μg/m3

 at the return and at or 

below 350 μg/m3

 at the working areas with the ventilation 

package and number and type of vehicles used. The 

concentrations of DPM achieved with similar ventilation 

packages can differ depending upon the vehicles used 

(number and type). 

The mine air in these mines was not below the final 

personal exposure limit (PEL) (160 μg/m3

 TC which would 

be represented by 123 μg/m3

 EC if one were to use the 

MSHA interim 1.3 TC/EC conversion factor – the 

conversion unit for the final limit has not been determined 
 

yet), but can still be beneficial in achieving the PEL. 

Higher ventilation will provide a mine more options of 

controls because not as much of a reduction would be 

needed to reduce the DPM down to the PEL. For example, 

biodiesel with a higher percentage of ultra low sulfur fuel 

could be used instead of 100% biodiesel or a diesel 

particulate filter. One could also use enclosed cabs and 

control the time that miners are outside the cabs (the better 

the ventilation, the longer a miner could be out of the cab 

before going above the PEL). At these mines, a miner 

could be in the atmosphere at the face for about 2.5 hours 

before reaching the PEL and could be exposed about 4-6 

hours in other parts of the mine before reaching the PEL. 

Such improved ventilation could also give the benefit of 

lowering the concentration of other possible irritants in the 

air. 

3.4 Enclosed Cabs 

As seen in the section above with the engines and 

ventilation package employed in these two mines, the mine 

air was not below the final PEL. Because the final PEL 

was not achieved at these mines, stone mines also used 

enclosed cabs to protect the miners. This has been shown 

to be an effective strategy in eliminating exposure of 

workers to contaminants when the cab is maintained 

well.11-13 In one stone mine (Mine C), miners in enclosed 

cabs were exposed to concentrations of DPM higher than 

the final limit (below interim limit). With the efficiencies 

reported in other studies, the concentrations measured in 

the enclosed cabs at this mine were unexpected. 

Therefore, NIOSH investigated the efficiency of these cabs 

to reduce DPM concentrations. NIOSH 5040 samples and 

EC monitors were placed inside and outside of a cab at 

Mine C. 

As seen in Figure 6, the reduction efficiency of the cab 

measured using NIOSH 5040 results was between 40-93% 

depending on the day and driver. One would not expect the 

reduction of DPM to vary this much from day to day just 

due to leakage or bad performance of the cab when nothing 

was done to the cab or vehicle, the sampling environment 

did not change drastically, and no trend was in the data 

(getting better or worse in each day). The real time data 

seems to indicate a possible reason for the variation. The 

real time data shows DPM peaks throughout the shift on 

days which display a lower reduction efficiency. This 

would indicate that the cab window and/or door was being 

opened periodically throughout the shift. 

This effect can be visualized when examining at a day 

with 73% cab efficiency compared to a day with 93% cab 

efficiency. The biggest difference between these days was 

only the driver. 

As seen in Figure 7, on the day with 73% efficiency, 

inside the cab for test 1, a peak of higher EC exposure for 

one part of the shift and then a higher exposure at the end 

of the sampling period are shown. The peak would indicate 

a window or door opening and then closing. The higher 

concentration at the end of the shift could be from the 

miner opening the window slightly and leaving it open for 

100 

80 

Efficiency (%) 

60 

40 

20 

0 

1 2 3 4 5 6 7 8 9 

Day 

 

 

Figure 6: Efficiency of the cab of a loader using the 

NIOSH 5040 data. 

800
 inside cab
 700
 outside cab
 600 

500 

400 

EC (ug/m3) 300 

200 

100 

0 

8:24 9:36 10:48 12:00 13:12 14:24 15:36 

Time 

Figure 7: The real time data comparing inside and outside 

of the cab on the day with 73% efficiency. 

the rest of the sampling period. If the EC exposure was due 

to a leak or penetration through the filtration system, one 

would expect the EC concentration to follow a trend and 

not expect to have a peak. 

As can be seen in Figure 8, unlike in test 1, the window 

or door does not seem to have been opened during the shift 

for test 2. It appears that after the first initial opening that 

the cab was closed for most of the day. The reduction 

efficiency from test 2 is probably closer to the expected 

efficiency of the cab. 

300 

800 outside cab 700 inside cab 600 

EC (ug/m3) 500 

400 

200 

100 

0 

8:24 9:36 10:48 12:00 13:12 14:24 15:36 16:48 

Time 

 

 

 

Figure 8: The real time data comparing inside and outside 

of the cab on the day with 93% efficiency. 

This cab should reduce DPM by over 90% when 

operating correctly and kept sealed. Work practices might 

be able to help minimize the opening of the windows and 

doors. 
 

 

 

 

4 Conclusion 

For the mines surveyed in this study, the ventilation 

controls used in conjunction with the number and type of 

engines operated in these two mines did not produce DPM 

concentrations below the final PEL. The controls used did 

lower the concentration enough to possibly give the mine 

more options in controlling the DPM exposures such as the 

time miners outside of an enclosed cab are working in 

certain areas of the mine. Enclosed cabs were also used in 

these mines to limit the exposure of the underground 

miners. In one mine, an enclosed cab was found to be over 

90% efficient in reducing DPM as long as the windows and 

doors were kept closed. The opening of windows seemed 

to cause a substantial increase in DPM exposure. Other 

studies have shown that along with keeping doors and 

windows closed good maintenance of the cabs is necessary 

for achieving good cab performance. Not all miners can be 

in enclosed cabs. For the miners outside of cabs, a different 

control needs to be used to reduce their DPM exposure 

such limiting the amount of time they work outside of a 

cab, restricting the areas where they work, lowering the 

DPM concentrations in areas of the mine through 

maintenance, improved ventilation, the use of diesel 

particulate filters, alternative fuels, or a combination of 

these engineering controls. 

This is some preliminary data. NIOSH is presently 

investigating various enclosed cabs to obtain a better 

understanding of how effective cabs are. Surveys are also 

continuing to investigate other types of DPM controls. 

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