4
stated that satisfactory results were obtained using a cus-
tom-built filter holder. The detection limit was found to be
approximately 20 µg quartz. There were drawbacks such as
vulnerability to light scattering and random noise associated
with the FTIR spectrometer when measuring the sample.
Another issue of note was the nonuniform deposition of
dust across the filter face. Recommendations were made to
use sampling cassettes that deposit the dust uniformly [25].
Work was initiated developing a method to quantify
silica on TEOM filters used by the CPDM by Tuchman.
This work developed a new filter using polyester and nylon
materials for the CPDM that were ashable, with the nylon
materials showing the most promising results. However,
the nylon filter material and filter body (polypropylene)
required longer ashing times than typical PVC filters.
Results of testing established that accuracies within 10%
with a precision of 5% were possible, demonstrating that
this filter was promising for silica quantification for CPDM
filters [26].
Miller et al. continued the research to investigate
using portable FTIR spectrometers for quantifying the
silica content on respirable coal mine dust samples. Issues
to overcome were the sensitivity of portable FTIR instru-
ments is less than laboratory instruments and the ability
to overcome minerals that interfere with free silica quanti-
fication. Coal dust samples were tested with two different
instruments (FTIR and variable filter array (VFA)) with
their results compared with the MSHA P7 method. Both
instruments showed promising results the FTIR was more
suitable for the coal samples, while the VFA was promis-
ing for pure silica samples [27]. Further research continued
using the FTIR spectrometer. This work included testing
the effects of nonuniformity/uniformity of dust deposition,
coal versus noncoal dusts, different filter material types, and
different calibration techniques [28, 29, 30, 31].
From this research and numerous additional studies
not noted here, the Field Analysis of Silica Tool (FAST)
was developed. The measurement process uses a Fourier
Transform Infrared (FTIR) spectrometer to analyze gravi-
metric filters. The software imports data from FTIR instru-
ments and translates the data into silica mass concentration
for each sample. While FAST can be used for determining
end of shift silica results from samples from commodities
other than coal, a disclaimer is made that other commodity
end of shift silica results should be considered approxima-
tions only [32].
For coal samples the results are comparable to MSHA
P7. However, it should be noted that the software calcula-
tions are based upon using 37 mm 5 µm pore PVC filters
in 4-piece conductive cassettes with stainless steel support
(instead of using a cellulose backing pad) or a capsule with
stainless steel support (also known as the coal sampling cas-
sette). Other recommended parameters for the instrument
settings are provided for resolution (4 cm–1), sample scan
time (16), background scan time (16), spectral range (4000
cm–1 -400 cm–1), result spectrum (Absorbance), phase cor-
rection (Mertz), apodization (Blackman Harris 3), and zero-
fill factor (2). Samples evaluated this field-based approach
are not considered for regulatory compliance [33], however
the filter can be sent off for further analysis.
Field analysis of silica is an important step in moni-
toring silica levels at the mine site. Being able to provide
end of shift silica results is an improvement in reducing
potential respirable silica dust exposures to miners. While
not real-time, these end of shift results are an improvement
to the previous method of sending the samples to a certi-
fied lab for analysis which can have long lead times. The
shorter lead time obtaining results will enable operators to
initiate controls for reducing potential respirable silica dust
exposures sooner, when warranted [34]. NIOSH contin-
ues to conduct research to improve the field-based method
of silica analysis and also continues to work to improve
the respirable dust and respirable silica dust measurement
methods.
EXTERNAL RESEARCH
The NIOSH mining program maintains a portfolio of
extramural contracts and grants awarded to institutions
and private entities to encourage the development and
manufacture of mine safety equipment, and to education
institutions or private laboratories for the performance of
product testing or related work with respect to new mine
technology or equipment. One of the purposes of these
contracts and grants is to enhance the development of new
technology and technological applications, and to expedite
the commercial availability and implementation of such
technology in mining environments [35]. This program
was established through the Mine Improvement and New
Emergency Response Act of 2006. [36].
In the recent past, contracts have been awarded that
are related to the topic of respirable dust characterization,
measurement, and control. The following describes active
contracts that are related to respirable silica dust in the cat-
egories of characterization studies and real-time respirable
silica monitors.
Characterization Studies
Characterization studies provide information on the min-
eral makeup of the sampled dust. The studies also include
documentation of particle size distributions and typical
stated that satisfactory results were obtained using a cus-
tom-built filter holder. The detection limit was found to be
approximately 20 µg quartz. There were drawbacks such as
vulnerability to light scattering and random noise associated
with the FTIR spectrometer when measuring the sample.
Another issue of note was the nonuniform deposition of
dust across the filter face. Recommendations were made to
use sampling cassettes that deposit the dust uniformly [25].
Work was initiated developing a method to quantify
silica on TEOM filters used by the CPDM by Tuchman.
This work developed a new filter using polyester and nylon
materials for the CPDM that were ashable, with the nylon
materials showing the most promising results. However,
the nylon filter material and filter body (polypropylene)
required longer ashing times than typical PVC filters.
Results of testing established that accuracies within 10%
with a precision of 5% were possible, demonstrating that
this filter was promising for silica quantification for CPDM
filters [26].
Miller et al. continued the research to investigate
using portable FTIR spectrometers for quantifying the
silica content on respirable coal mine dust samples. Issues
to overcome were the sensitivity of portable FTIR instru-
ments is less than laboratory instruments and the ability
to overcome minerals that interfere with free silica quanti-
fication. Coal dust samples were tested with two different
instruments (FTIR and variable filter array (VFA)) with
their results compared with the MSHA P7 method. Both
instruments showed promising results the FTIR was more
suitable for the coal samples, while the VFA was promis-
ing for pure silica samples [27]. Further research continued
using the FTIR spectrometer. This work included testing
the effects of nonuniformity/uniformity of dust deposition,
coal versus noncoal dusts, different filter material types, and
different calibration techniques [28, 29, 30, 31].
From this research and numerous additional studies
not noted here, the Field Analysis of Silica Tool (FAST)
was developed. The measurement process uses a Fourier
Transform Infrared (FTIR) spectrometer to analyze gravi-
metric filters. The software imports data from FTIR instru-
ments and translates the data into silica mass concentration
for each sample. While FAST can be used for determining
end of shift silica results from samples from commodities
other than coal, a disclaimer is made that other commodity
end of shift silica results should be considered approxima-
tions only [32].
For coal samples the results are comparable to MSHA
P7. However, it should be noted that the software calcula-
tions are based upon using 37 mm 5 µm pore PVC filters
in 4-piece conductive cassettes with stainless steel support
(instead of using a cellulose backing pad) or a capsule with
stainless steel support (also known as the coal sampling cas-
sette). Other recommended parameters for the instrument
settings are provided for resolution (4 cm–1), sample scan
time (16), background scan time (16), spectral range (4000
cm–1 -400 cm–1), result spectrum (Absorbance), phase cor-
rection (Mertz), apodization (Blackman Harris 3), and zero-
fill factor (2). Samples evaluated this field-based approach
are not considered for regulatory compliance [33], however
the filter can be sent off for further analysis.
Field analysis of silica is an important step in moni-
toring silica levels at the mine site. Being able to provide
end of shift silica results is an improvement in reducing
potential respirable silica dust exposures to miners. While
not real-time, these end of shift results are an improvement
to the previous method of sending the samples to a certi-
fied lab for analysis which can have long lead times. The
shorter lead time obtaining results will enable operators to
initiate controls for reducing potential respirable silica dust
exposures sooner, when warranted [34]. NIOSH contin-
ues to conduct research to improve the field-based method
of silica analysis and also continues to work to improve
the respirable dust and respirable silica dust measurement
methods.
EXTERNAL RESEARCH
The NIOSH mining program maintains a portfolio of
extramural contracts and grants awarded to institutions
and private entities to encourage the development and
manufacture of mine safety equipment, and to education
institutions or private laboratories for the performance of
product testing or related work with respect to new mine
technology or equipment. One of the purposes of these
contracts and grants is to enhance the development of new
technology and technological applications, and to expedite
the commercial availability and implementation of such
technology in mining environments [35]. This program
was established through the Mine Improvement and New
Emergency Response Act of 2006. [36].
In the recent past, contracts have been awarded that
are related to the topic of respirable dust characterization,
measurement, and control. The following describes active
contracts that are related to respirable silica dust in the cat-
egories of characterization studies and real-time respirable
silica monitors.
Characterization Studies
Characterization studies provide information on the min-
eral makeup of the sampled dust. The studies also include
documentation of particle size distributions and typical