James D. Noll,1 Robert J. Timko,1 Linda McWilliams,1 Peter Hall,2

and Robert Haney3

1 Pittsburgh Research Center, National Institute for Occupational Safety and Health,

Pittsburgh, Pennsylvania

2SKC, Inc., Eighty Four, Pennsylvania

3Mine Safety and Health Administration, Pittsburgh, Pennsylvania

Diesel particulate matter( D PM) samplesfrom underground

metal/nonmetal mines are collected on quartz fiber filters and

measured for carbon content using National Institute for Occupational Safety and Health Method 5040. If size-selective

samplers are not used to collect D PM in the presence of carbonaceous ore dust, both the ore dust and D PM will collect on

the quartzfilters, causing the carbon attributed to D PM to be

artificially high. Because the D PM particle size is much smaller

than that of mechanically generated mine dust aerosols, it can

be separatedfrom the larger mine dust aerosol by a single-stage

impacto1: The SKC D PM cassette is a single-stage impactor

designed to collect only D PM aerosols in the presence of

carbonaceous mine ore aerosols, which are commonly found in

underground nonmetal mines. Howeve1: there is limited data on

how efficiently the SKC D PM cassette can collect D PM in the

presence of ore dust. In this study we investigated the ability of

the SKC D PM cassette to collect D PM while segregating ore

dust from the sample. We found that the SKC D PM cassette

accurately collected D PM. In the presence of carbon-based

ore aerosols having an average concentration of 8 mg/m3, no

ore dust was detected on SKC D PM cassette filters. We did

discover a problem: the surface areas of the D PM deposits

on SKC D PM cassettes, manufactured prior to August 2002

were inconsistent. To correct this problem, SKC modified the

cassette. The new cassette produced, with 99% confidence, a

range of D PM deposit areas between 8.05 and 8.28 cm2, a

difference of less than 3%.

Keywords carbon, diesel particulate matter, dust, impactor

5040-as a surrogate for determining D PM exposures.(I--

MSHA personnel use the 1973 sampling criteria outlined by

the American Conference of Government Industrial Hygienists (ACGIH@) for collecting compliance-based respirable and

inhalation samples in metal/nonmetal mines.(5,6)

D PM is within the aerodynamic particle size range of the

samplers used for respirable and inhalable dust measurements

Therefore, if a sampler used by MSHA to collect inhalable o

respirable dust samples in underground metal/nonmetal mines

was used to collect D PM, both the D PM and mine ore dus

would accumulate on the sample filter. When sampling fo

D PM in carbonaceous mines, the carbon attributed to D PM

would thus be artificially high.

To solve this problem, U.S. Bureau of Mines (BOM) re

searchers developed a size-selective sampler that allowed only

particulate matter with an aerodynamic diameter less than

0.8 .urn .to pass through the device and be collected on a

downstream filter. (7-9) Since the aerodynamic diameter of mos

ore dust is typically greater than 0.8 .um, and the aerody

namic diameter of most D PM is less than 0.8 .um,(7) the impactor segregates most of the D PM from most of the ore dus

and permits only D PM to be collected. Research results show

that the classification efficacy, in preventing coal dust to pas

through this impactor, is greater than 90%.(9)Currently, SKC

Inc. (Eighty Four, Pa. ) manufactures the D PM cassette that wa

designed from the BOM impactor. It has the same cut point and

impaction design as the BOM impactor. This device is being

used to collect D PM in noncoal mines.

Data confirming the accuracy of the SKC D PM cassette is

limited. Some in the mining industry have brought up concern

with SKC D PM cassette performance and possible defects.(IO

In this study we examined the performance of the SKC D PM

cassette. We first determined the ability of the cassette to collect D PM by comparing D PM samples collected with SKC

D PM cassettes with respirable samples (which represent the

D PM concentration "standard" since they will collect all o

the D PM). We performed these tests in the laboratory and a

he Mine Safety and Health Administration (MSHA)

rule governing diesel particulate matter (D PM) exposures in metal and nonmetal mines cites total

, carbon (TC)-a summation of elemental carbon

(EC) and organic carbon (OC) obtained by National Institute for Occupational Safety and Health (NIOSH) Method

Journal of Occupational and Environmental Hygiene January 2005 29

Address cocrespondence to: James D. No11, Pittsburgh Research

Center, National Institute for Occupational Safety and Health, 626

Cochrans Mill Road, Pittsburgh, PA 15236; e-mail: jin1 @cdc.gov.
overload the impaction plate when exposed to high levels of

dust. Dust particles greater than 3.5 Jl,m can be eliminated by

the cyclone and reduce the chance of overloading the impactor.

BOM Impactor/Carbon Analysis

Two quartz fiber filters were baked for at least 2 hours at

800°C to drive off any OC. These filters were inserted, in

tandem, into a three-piece MSA cassette. Each cassette was

sealed to prevent air leakage. The MSA cassette was placed

immediately downstream of a BOM aluminum impactor and

a Dorr-Oliver cyclone.

Design I SKC D PM Cassette/Carbon Analysis

The SKC D PM cassette (Figure la) was placed in series

downstream of a Dorr-Oliver cyclone. The SKC D PM cassette

contained two quartz filters in tandem behind an impactor

with O.8-ttm cut point. Each quartz filter was wrapped with

an aluminum shield as shown in Figure I b.

having an atmosphere that contained only mineral dust and

measuring the quantity of mineral dust collected on the filters.

Early in this evaluation we discovered problems with the

SKC D PM cassette. In many experiments; the surface areas

of D PM deposited on the filters were irregular. These areas

also varied between cassettes. The discoveries forced the research protocol to be modified. First, the irregularly shaped

D PM deposit area of every SKC D PM cassette filter had to be

determined, since the area was different for each filter. Because

the deposit area is used to calculate the aerosol concentration,

any measurement error will cause inaccurate results when calculating the concentration ofTC and EC. Second, the difficulty

associated with measuring the irregular shapes could result in

some error when determining deposit areas.

To solve the problem, the SKC D PM cassette design was

modified to produce a consistent D PM deposit area. Following

the modifications, we performed" tests to verify that the SKC

D PM cassette produced a reliable and uniform deposit area by

measuring the deposit areas from D PM samples collected in

the laboratory and in the field.

Design II SKC D PM Cassette/Carbon Analysis

This design is similar to Design I except that the aluminum

shield is removed. Additionally, a metal gasket is placed in

front of the quartz filters as shown in Figure lc.

METHODS

Sampler Preparation

The following sections describe the preparation required

for each sampler type used in both laboratory and field

experiments.

Respirable Sampler/Gravimetric Analysis

This sampler was the same setup used by MSHA to collect

respirable samples for dust containing silica (a PVC filter

behind a Dorr.Oliver cyclone having a D50 cut point of 3.5 .urn

at a 1.7 L/min flow rate). This methodology is also described

by ACGIH@.(5.6)

Gravimetric samples were equilibrated and pre. and post.

weighed in a controlled environment that was set at 72°F and

50% relative humidity. Balance precision was better than 5 .ug.

Blank filters were also weighed before and after each set of

samples.

Laboratory Experimental Error

An aerosol chamber( 1 1) capable of dispersing D PM and dust

uniformly throughout its midsectional volume was used in all

laboratory evaluations. Ideally, samplers located in the same

plane should be sampling equal D PM mass. However, due

to spatial variation, small errors were possible. In addition,

the NIOSH- Method 5040 analytical method contributed to

experimental error. Conversely, the sampler airflow should not

be a significant contributor to error since critical orifices, whose

fluctuations were negligible, controlled the airflows through all

samplers used for all chamber evaluations. Flow rates of the

critical orifices were checked periodically with an electronic

soap film flow meter calibration device (Gilibrator, Gillian

Instrument Group, West Caldwell, N.J.).

The following experiments were run to determine the experimental error when collecting D PM in the chamber. Three

respirable samplers with quartz filters for carbon analysis were

placed at the same height inside the aerosol chamber. Exhaust

emissions from a Kubota diesel engine attached to a 10 kW

generator provided D PM in the chamber. Air samples were

taken within the chamber for a specific duration. Each sample

was then analyzed using NIOSH Method 5040 to determine

the uniformity of D PM dispersion across the chamber. This

experiment was repeated II additional times for different D PM

concentrations and different engine loads yielding 12 triplicate

samples representing different OC-to- TC ratios.

Respirable Sampler/Carbon Analysis

Two prebaked quartz fiber filters were inserted in tandem (a

second quartz filter is placed behind the primary filter) into a

Mine Safety Appliances Company (MSA) three-piece cassette.

Each cassette was sealed with an air compressing system and

was attached to a Dorr-Oliver cyclone.

BOM Impactor/Gravimetric Analysis

A BOM aluminum impactor was placed in series between

the Dorr-Oliver cyclone and the filter cassette that was described above. Since the BOM aluminum impactor only allows

particles with an aerodynamic diameter less than 0.8 .urn to

30 Journal of Occupational and Environmental Hygiene January 2005
each cassette.

For at least an hour, an aerosol chamber sample was collected for carbon analysis at 1.7 L/min by one of the respirable

samplers. At the end of the hour, the sampler was removed

from the chamber. This sample was considered the chamber

blank. It quantified the background OC present in the chamber

air before diesel exhaust was added.

The chamber was sealed again and the Kubota diesel engine was started. A tapered element oscillating microbalance

(TEOM), designed to measure the ambient particulate mass

in real time, was used to monitor diesel exhaust concentration. When the TEOM indicated steady D PM levels inside

the aerosol chamber, air pumps drawing on the critical orifices connected to the various samplers were switched on.

Sampling continued until a D PM filter loading of between 10

and 40 ILg/cm2 was attained, as estimated by the TEOM. The

air pumps were switched off and the D PM was permitted to

exhaust from the chamber. The samples were then removed and

plastic plugs inserted into each filter cassette's inlet and outlet

to isolate the cassette from the surrounding environment. The

above procedure was repeated under different engine loads to

achieve a variety of OC-to- TC ratios. Finally, each sample was

analyzed for EC and TC using NIOSH Method 5040.

FIGURE 1. SKC D PM cassette: (A) The main casing used for

both Design I and Design II. (8) Design I (manufactured before

August 2002) and (C) Design II (instead of aluminum shield, a

metal gasket followed by two quartz filters and a backing pad are

used in this design)

Field Experiments

The ability of the SKC D PM cassette to collect D PM was

also tested in an underground mine. In Mine 1, three samples

using SKC D PM cassettes and three samples using respirable

samplers (carbon analysis) were collected with MSA Elf sampiing pumps operating at 2 L/min in an isolated area, a location

where no ore dust was produced. The SKC D PM cassette

was designed to collect D PM at flow rates of 1.7 or 2 L/min.

Impactor cut points were 0.73 .urn at 2 L/min and 0.8 .urn at

1.7 L/niin. MSHA uses a flow rate of 1.7 Umin when sampling

aerosols in metal/nonmetal mines and 2 L/min when sampling

aerosols in coal mines. The metal/nonmetal regulations were

based on the 1973 ACGIH sampling criterion,(5,6) and the coal

mine regulations were based on the British Medical Research

Council sampling criterion.(12) The 2 L/min flow rate, used in

coal mines, was believed to give a better estimate, with a correction factor, of the Mining Research Establishment (London,

England) gravimetric dust sampler, which has a four-channel

horizontal elutriator. This field data was originally obtained to

investigate D PM concentrations in coal mines, so a 2 L/min

flow rate was used.

Since the cut point at 2 L/min is smaller than at 1.7 L/min,

D PM collection will potentially be more hindered when using

2 L/min rather than 1.7 Umin. Therefore, if most of the D PM

is collected at 2 L/min, one would expect even better D PM

collection efficiency using 1.7 Umin. When looking at the

size distribution of D PM, there does not seem to be a large

portion of D PM within 0.73 and 0.8 .urn to make a significant

difference when using the two different flow rates.(7)

D PM Collection Efficacy

Laboratory Experiments

To detennine the efficacy of the SKC D PM cassette to

collect D PM, three SKC Design lor Design II D PM cassettes,

three BOM impactors (carbon analysis), and four respirable

Journal of Occupational and Environmental Hygiene January 2005 31
(ILg/

(JLg/m3)A

for ECfor TC

{/Lg/m3)A

Set

(fLg/m3)A

201

214

274

302

737

217

225

290

323

794

242

261

321

358

1041

261

272

344

360

129

5.4

3.5

4.0

4.8

5.3

5.3

2.9

4.9

0.4

5.7

'+

5

Each value represents the average of triplicate samples.

ICY = (standard deviation (EC [SKC], EC [respirable])/average (EC [SKC], EC [respirable])) x 100, e.g., sample set I: CY for EC = standard deviation (201

17)/average (201, 217) x 100.

.CY for TC is calculated the same way as the EC.

'Design I SKC D PM cassettes were used with this experiment. Design II SKC D PM cassettes were used for the other experiments

To generate D PM, diesel-powered mining machines were

driven back and forth in the isolated area. Each procedure was

repeated five times for different vehicles and loads as well

as with and without engine exhaust filters. All samples were

analyzed for carbon using NIOSH Method 5040.

Method 5040 analysis of the respirable quartz filter samples

to the gravimetric mass of the respirable gravimetric samples.

A Marple Series 290 Personal multistage cascade impactor

(Andersen Instruments, Smyrna, Ga.) was run at 2 L/min to

establish the dust particle size distribution.

SKC Cassette D PM Deposition

To determine the D PM deposition patterns of the Design

I SKC D PM cassettes, we collected air samples from two

different mines: Mine I, described previously, and Mine 2,

a metal mine where samples were collected at a 1.7 Umin

flow rate. The deposit area of each filter was measured and

photographed. For each filter, the surface area of D PM deposit

was determined by using a calibrated caliper to measure two

deposit diameters that were oriented perpendicular to each

other. The average of the two diameters was used to compute

the approximate area of the deposit using the equation for the

area of a circle.

We determined D PM deposition patterns of the Design

II SKC D pM cassettes by collecting D PM on SKC D PM

cassettes in the laboratory chamber using a procedure similar

TABLE II. Field Data Comparing SKC D PM Cassettes with Respirable Samplers

.

(fLg/m3)A (fLg/m3)A CV (%)8 CV (%)

Sample

Set

409

670

335

3244

77

410

725

399

3347

84

0.2

5.6

12.3

2.2

6.1

12

12

12

12

12

1

2

3

4

~

Ore Dust Collection Efficiency

Laboratory Experiments

To determine how well the SKC D PM cassette rejects nonD PM dusts, we modified the experiments described above by

introducing ore dust instead of D PM into the aerosol chamber

for 3 hours at an average concentration of 8 mg/m3. In addition

to three SKC Design lor Design II D PM cassettes, one BOM

impactor (carbon analysis), and four respirable samplers (carbon analysis) that were mentioned in the previous chamber

experiment, three respirable gravimetric samplers and three

BOM impactor/gravimetric samplers were also placed into the

chamber. The ore dust consisted of actual bulk ore samples

that were subsequently crushed at Pennsylvania State University and processed to have the same size distribution as the

aerosol found at that particular nonmetal mine. The dust was

introduced to the chamber by a fluidized bed aerosol generator.

A comparison of the gravimetric mass collected on the

respirable dust filters with that collected on the filters following the BOM impactor yields the effectiveness of the BOM

impactor to avoid respirable ore dust from this mine. Since

the SKC D PM cassette was designed from the BOM impactor,

the efficacy of the BOM impactor should be similar to that

of the SKC D PM cassette. SKC D PM cassettes themselves

cannot be used in this experiment, since their filters cannot

be removed for preweighing. Carbonate carbon analysis of the

SKC D PM cassettes would show if a significant amount of

ore dust collected on the SKC D PM cassette (described in

more detail in the Ore Dust Separation section).

Three respirable samplers with quartz filters (carbon sampIers) were used to determine the carbon mass fraction in

the ore dust. We determined the percentage of carbon in the

ore dust by comparing the carbon obtained through NIOSH

A Each value represents the average of

B CY = (standard deviation (EC [SKC

EC [respirable])) x 100, e.g., sample

(409, 410)/average (409,410) x 100.

32 Journal of Occupational and Environmental Hygiene January 2005

m3)A

SKC D PM Between

Cassettes Respirable SKC and Experimental

RC EC Resoirahle Error

triplicate samples.

I, EC [respirable])faverage (EC [SKC],

set I: CY for EC = standard deviation
21.30

14.80

9.80

6.00

3.50

1.55

0.93

0.52

0.00

25.46

25.84

25.89

25.54

25.32

25.04

25.63

25.21

13.49

25.52

25.89

26.02

25.98

26.22

25.93

25.80

25.21

13.50

0.52

0.61

0.78

0.89

0.95

0.96

0.97

0.99

1.00

Total

0.10

0.08

0.17

0.49

0.95

0.93

0.18

0.00

0.01

2.90

3.

2.

5.

16.

32.

32.

6.

0.

0.

2

3

4

5

6

7

8

Final

AThe correction factor is a factor to correct for sampling efficiency and internal losses when using the Marple cascade impactor. The mass is divided

correction factor on the impactor stage to give the corrected mass.

in each of 12 experiments. The 12 CYs were then pool

according to NIOSH Guidelines for Air Sampling and An

lytical Method Development and Evaluation(15) to obtain 

95% upper confidence limit for an experimental error C

The Bartlett test was then performed on the data to confir

homogeneity of the data set. The 95% upper confidence lim

for experimental-error CY was 7% for EC measurements a

6% for TC measurements.

to that outlined in the D PM Collection Efficacy, Laboratory

Experiments section. Each. filter was photographed, and the

deposit area was measured as described above. The procedure

for measuring the deposit area was then followed for D PM samples taken from several mines with SKC D PM cassettes. Field

samples using a 1.7 L/min flow rate were taken at different

locations in several mines. The deposit areas were measured

for each filter. In total, 94 samples were collected to determine

the variance of the deposit area.

Field Experiments

Field sampling error was found by taking the root me

square (rms) of three possible sources of error: NIOSH Meth

5040, pump flow, and deposit area determination. A NIOS

Method 5040 analytical error CY of 10% (95% pooled CY 

50 D PM samples taken from mines) for EC was taken fro

the literature.(16) We used a CY of 5% for pump flow err

RESULTS AND DISCUSSION

Interferences

In the laboratory experiments when just D PM was released

into the chamber, no sources of EC or TC particulate other than

D PM were present. This was shown by the concentrations of

EC and TC in the chamber blanks, corrected for vapor phase

OC, being below the limit of detection. Vapor phase OC did

adsorb onto the quartz filter and caused a positive bias of TC

from the D PM results. OC levels on a second filter, inserted

in tandem with the first or primary filter, were subtracted from

the primary filter OC values to correct for the vapor phase

OC.(13.14) In theory, the second filter should not be exposed to

the aerosol OC but should adsorb the same amount of vapor

phase OC as the primary filter.

In the field study collecting only D PM, no dust was present

in the isolated zone; therefore, no sources of EC other than

D PM were present in the isolated zone atmosphere. EC results

from D PM collected by the SKC D PM cassettes were compared with D PM EC collected by the conventional respirable

samplers to indicate whether the SKC D PM cassettes were

collecting all of the D PM.

Coefficient of Variation

Laboratory Experiments

To determine the variation of samples in the laboratory

chamber, a coefficient of variance (cY) was calculated for the

NIOSH Method 5040 results of the three respirable samplers

Journal of Occupational and Environmental Hygiene January 2005 
Sample Type 

(g) 

(g) 

(g) 

(g) 

O(Jg/3)

97.49

9.38

10.05

133.77

4.41

<5.59

394.57

<3.77

<5.59

625.84

17.21

15.35

5.59

3.77

5.59

RespirableA

SKC impactorsA

BOM impactorsB

A Each value represents the average of triplicate samples.

BThese results are from a single sampler.

FIGURE 3. Filters that collected D PM from Design I SKC D PM cassette

34 Journal of Occupational and Environmental Hygiene January 2005
The error in the deposit area was calculated by measuring the

diameter of the same deposit area several times and calculating

a cy between measurements. The cys of the measurements

from several filters were pooled according to NIOSH Guidelines for Air Sampling and A,!alytical Method Development

and Evaluation, and the percent error in measuring the deposit

area was about 4%. The fillS of the three CY s was 12%.

SKC Cassette D PM Performance

SKC D PM cassettes were found to be very efficient for sampling D PM. In the laboratory experiments where the Design I

and Design II SKC D PM cassettes and respirable samplers

were exposed to D PM, the variation between EC and TC

concentrations of the two sampler types were within the errors

of the experiment (the CY between samplers was less than

the 95% upper confidence limit for the experimental error), as

shown in Table I.

As seen in Table II, field tests also showed that the SKC

D PM cassettes collected D PM efficiently. The variation between the EC concentrations derived from air samples containing D PM collected with the Design I SKC D PM cassettes

and with the respirable samplers in Mine I were less than or

equal to the experimental error variation.

EC concentrations were always lower when collected with

the SKC D PM cassette. This may have been because agglomerated D PM particles did not pass through the cassette. Nevertheless, EC concentrations measured by the respirable samplers

and the SKC D PM cassettes were still within experimental

error.

FIGURE 5. Pictures of filters that collected D PM with Design II

of the SKC D PM cassette.

Ore Dust Separation

The SKC D PM cassette also prevented most of the airborne

ore dust from passing through the classifier and collecting

on the filter. As seen in Table III, about 6% (190 JLg) of the

ore in the chamber had a particle diameter less than 1.55 JLm

and approximately 0.31% (10 JLg) was less than 0.5 JLm. The

BOM impactor/gravimetric samplers collected only about 2%

(40 JLg) of the 2.26 mg respirable dust load. This device was

98% efficient in preventing ore dust from collecting on the

filter. We would expect similar results from the SKC D PM

cassettes because the two samplers have the same cut point

and similar designs.

Carbon analysis showed similar results. In NIOSH Method

5040, the temperature is ramped up in four steps in a helium

atmosphere to evolve all of the OC. When carbonate is present,

a sharp peak should be detected when the temperature is about

870°C. This peak is absent if D PM is the only particulate

present on the filter.

The carbon present in the ore consisted mostly of carbonate

(CC), for the ore dust was 8.49% carbon with 63% of that

carbon being carbonate. Because a significant amount of ore

dust reached the filter on the respirable dust sampler, a CC peak

is readily visible on the carbon analysis thermogram, as shown

in Figure 2. In Table IV, CC was detected when respirable

Journal of Occupational and Environmental Hygiene January 2005 35
7.40

7.20

7.00

20 30 40 50

number

60 70 80 90 100

t

o 10

FIGURE 6. Ninety-four deposit areas of filters from Design II SKC D PM cassette (field and laboratory samples). The dotted lines are the upper

and lower control limits,

deposit area), the 99% confidence range for a sample with

10 JLg/cm2 carbon analysis ranged between 74-110 JLg/m3 for

Mine 1 and 54-123 JLg/m3 for Mine 2, a difference of over

40%. Because of this large spread of areas, we decided that

the deposition area of each SKC D PM cassette would have to

be measured. Even then, slight errors would most likely occur

due to the irregular shapes of the deposits. As a result, efforts

were made to alleviate the irregular and inconsistent deposition

area.

samplers were used, but no CC above the limit of detection

(LOD) was found on filters taken from BOM impactors or

SKC D PM cassettes. The LOD for NIOSH Method 5040 is

0.2 JLg/cm2 per filter section fora 1.5 cm2 punch.(4) In Table IV,

this LOD was converted to concentration.

These laboratory results confirmed field data obtained in an

MSHA four-mine stucty.(9) MSHA personnel collected samples

from four different metal and nonmetal mines. Samples were

taken from four areas of each mine. When researchers used

the BOM impactor, the mass detected was about 94% less than

that found on respirable sampler filters. Ideally, SKC D PM

cassettes should behave in a similar manner. Ore samples from

operations milling carbonaceous ores had a high percentage

of CC; therefore, if ore dust was penetrating the impactor and

causing an artificial increase in the carbon detected, a CC peak

should have been evident in the thermogram. However, when

the SKC D PM cassette was used, no carbonate peak and no

TC values significantly above blank values were seen.

Design I SKC Cassette D PM Deposit Area

A problem was observed when using the Design I SKC

D PM cassettes. Figure 3 shows that the areas of D PM deposition when using pesign I SKC D PM cassettes were often

irregular instead of circular. As seen in Figure 4, in Mines 1

and 2 the exposed filter areas for the SKC D PM cassette ranged

from about 6 to 9 cm2. The controllirnit range, the 3-sigma

(3(1 ) range, of deposit areas for the SKC D PM cassettes in Mine

1 were 4.4tolO cm2. The 3(1 range of deposit areas for Mine 2

was 6to 9 cm2. Since a constant deposit area is usually assumed

(and desirable to avoid the extra effort required to determine

Design II SKC Cassette D PM Performance

The Design I SKC D PM cassette contained an aluminum

foil shield to protect the filter. We believe this shield was

responsible for the irregular and inconsistent D PM dispersion

areas. During cassette assembly, as the two plastic cassette

halves were joined, the aluminum shield tended to crimp. This

resulted in a deformation of the filter medium and caused

varying filter-to-shield contact near the filter perimeter.

The Design I cassette was modified by removing the aluminum shield and placing a thin metal annulus, a 37 mm

outer diameter and 32 mm inner diameter gasket, in front

of the quartz filter. The area inside the gasket was 8.04 cm2.

The gasket provided strength, reduced filter deformation, and

afforded a definite boundary for D PM deposition.

Design II was tested in the laboratory in a DPM-only atmosphere. As can be seen in Figure 5, the cassettes' deposit

areas looked regular and consistent. The control limit range of

the deposition was between 8.11 and 8.21 cm2, a difference of

less than 2%. After this initial test of the Design II cassette,

deposition areas of 94 Design II SKC D PM cassette filters

Journal of Occupational and Environmental Hygiene January 2005
8.28 cm2, a difference of less than 3%. The 99% confidence

range for a 10-JLg/cm2 carbon analysis with the assumption of

a constant deposit area would be 99-101 JLg/m3, a difference of3%. .

CONCLUSIONS

s KC D PM cassettes efficiently collected D PM in both laboratory and field evaluations. In addition, no carbon from

ore dust was detected when sampling in an 8 mg/m3 atmosphere of metal mine ore. Results of the Design I SKC D PM

cassette evaluation found irregular and inconsistent deposit

areas. If Design I SKC D PM cassettes are used, the exposed

filter area should be determined for each cassette. Design II

adequately solved this probJem and produced regular and consistent D PM deposit areas across the filter surface. The Design

II version of the SKC D PM cassette is presently in production.

REFERENCES

Mines, Federal Register 30:57 (1991) p. 393.

6. American Conference of Government Industrial Hygienists

(ACGIH@): TLVs Threshold Limit Values for Chemical Substances in

Workroom Air Adopted by ACGIH for 1973. Cincinnati, Ohio: ACGIH,

1973.

7. Cantrell, B.K., and K.L. Rubow: Development of personal diesel aeroso

sampler design and performance criteria. Min. Eng. 43:232-236 (1991).

8. McCartney, T.C., and B.K. Cantrell: A cost-effective personal diese

exhaust aerosol sampler. In Diesels in Underground Mines: Measuremen

and Control of Particulate Emissions (Information Circular 9324)

Proceedings of the Bureau of Mines Information and Technology Transfe

Seminar, Minneapolis, Minn., September 29-30, 1992.

9. Cantrell, B.K., and W. F. Watts, Jr.: Diesel exhaust aerosol: Review

of occupational exposure. Appl. Occup. Environ. Hyg. /2:1019-1027

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