4
a Gilibrator (Sensidyne., St. Petersburg, FL) as described by
Bugarski et al. (2012).
FLIR Airtec monitors (Teledyne FLIR, Stillwater, OK)
were used to provide near-real-time EC data (Noll et al.
2013). This instrument, which was developed at NIOSH
(Pittsburgh, PA) measures near-real-time EC concentra-
tions. A diaphragm pump draws EC-laden air, at a set flow
rate of 1.7 lpm, through an impactor with a 1-μm size
cut-point where the EC is collected onto a 37-mm Teflon
filter, housed in a three-piece standard cassette to achieve
uniform distribution of EC on the filter. A laser penetrates
through a portion of the sample simultaneous with the col-
lection of DPM, and the absorption of the laser’s energy is
measured and converted to μg of EC collected on the filter
using a calibration curve. The instrument collects a reading
every minute and provides the average concentration over
the past 5–15 min (5–15 min rolling averages), depending
on DPM concentration.
EC was used as a surrogate to determine the uniform
distribution of DPM. Since EC is a major component of
DPM, it has been shown to provide a consistent represen-
tation of DPM in underground mines and is used as a sur-
rogate for DPM by NIOSH and MSHA. EC can also be
measured at lower concentrations than total carbon mea-
surements and is not prone to interferences (Noll et al.
2006, 2015, 2019).
DPM Reduction Efficiency with Direct Reading
Instruments
A metal grid, measuring approximately 3ft × 3ft, was
hung 15 inches below and parallel with the DCAC ple-
num (Figure 5), as discussed in the air velocity profile sec-
tion. DPM measurements were collected using both an
Aerodynamic Particle Sizer (APS, model 3201, TSI Inc.,
particle size range 0.5–20 μm) and a NanoScan (model
3910, TSI Inc., particle size range 11.5–365 nm) at 25
(5×5) sampling points evenly spaced on the sampling grid.
Test Procedure
Three SKC DPM cassettes with MSA ELF pumps and one
Airtec instrument were placed in a basket 2 feet directly in
front of the canopy air curtain (CMine). Three SKC DPM
cassettes as well and one Airtec monitor were also placed in
a basket located under the DCAC, 15 inches below (to sim-
ulate the breathing zone of a male at average height) and in
the direct center (CDCAC) as shown in Figure 5. One Airtec
monitor was also placed next to the V-bank filter housing
located in the rear of the test section. This data was used to
calculate DPM loading onto the filter potentially resulting
in decreased DCAC flow.
DPM was introduced into the chamber from the
Onan diesel generator (Cummins Inc., Gibsonia, PA). A
seventy-two percent (72%) load was applied to the genera-
tor by a Simplex Swift-e plus 15-kW portable load bank
(Simplex, Springfield, IL). At this loading, the EC-to-TC
ratio approximates the composition observed in under-
ground mines (Noll et al. 2015). The generator was run for
45 minutes to stabilize the DPM concentration within the
test section. DPM stabilization was measured, during this
45-minute period, using both the Airtec and the real-time
instruments.
After the 45-minute stabilization period, the DCAC
flow was initiated. The DPM cassette pumps were started
after an additional 10-minute stabilization period and sam-
pled for 120 minutes, after which they were stopped.
The quartz filter samplers were analyzed for elemen-
tal carbon (EC) using NIOSH Method 5040 at NIOSH
Pittsburgh. EC is used as a surrogate for DPM for MSHA
sampling. The average of the three samples outside of and
under the DCAC were calculated. The percent (%)DPM
reduction due to the DCAC (EDPM, %)was calculated for
each test using equation (1):
E C
C
100
DPM
Mine
DCAC #=-^%h c1 m (1)
The percent reductions for each test were averaged, and
a standard deviation was calculated.
The ,(%)was calculated for the Airtec instrument data
by averaging the rolling averages over the time the DCAC
was running for both the instruments located under and
outside of the DCAC, then applying equation (1).
The DPM number concentration of the Experimental
Mine, not under the DCAC ,was first measured with the
APS and NanoScan and was immediately followed by
a measurement of the DPM concentration beneath the
DCAC at one of the 25 sampling points. Air sampling for
both APS and NanoScan was conducted simultaneously
for one minute by using a Y-shaped stainless-steel tube and
conductive tubing that was for splitting the airflow to the
APS and NanoScan. A total of 25 aerosol concentrations
of the Experimental Mine and 25 DPM concentrations for
each sampling point beneath DCAC were measured with
three repetitions. The DPM reduction efficiency (,%)of
the DCAC was determined by the following equation (2):
E CMine
C
100
DPM
DCAC #=-^%h c1 m (2)
a Gilibrator (Sensidyne., St. Petersburg, FL) as described by
Bugarski et al. (2012).
FLIR Airtec monitors (Teledyne FLIR, Stillwater, OK)
were used to provide near-real-time EC data (Noll et al.
2013). This instrument, which was developed at NIOSH
(Pittsburgh, PA) measures near-real-time EC concentra-
tions. A diaphragm pump draws EC-laden air, at a set flow
rate of 1.7 lpm, through an impactor with a 1-μm size
cut-point where the EC is collected onto a 37-mm Teflon
filter, housed in a three-piece standard cassette to achieve
uniform distribution of EC on the filter. A laser penetrates
through a portion of the sample simultaneous with the col-
lection of DPM, and the absorption of the laser’s energy is
measured and converted to μg of EC collected on the filter
using a calibration curve. The instrument collects a reading
every minute and provides the average concentration over
the past 5–15 min (5–15 min rolling averages), depending
on DPM concentration.
EC was used as a surrogate to determine the uniform
distribution of DPM. Since EC is a major component of
DPM, it has been shown to provide a consistent represen-
tation of DPM in underground mines and is used as a sur-
rogate for DPM by NIOSH and MSHA. EC can also be
measured at lower concentrations than total carbon mea-
surements and is not prone to interferences (Noll et al.
2006, 2015, 2019).
DPM Reduction Efficiency with Direct Reading
Instruments
A metal grid, measuring approximately 3ft × 3ft, was
hung 15 inches below and parallel with the DCAC ple-
num (Figure 5), as discussed in the air velocity profile sec-
tion. DPM measurements were collected using both an
Aerodynamic Particle Sizer (APS, model 3201, TSI Inc.,
particle size range 0.5–20 μm) and a NanoScan (model
3910, TSI Inc., particle size range 11.5–365 nm) at 25
(5×5) sampling points evenly spaced on the sampling grid.
Test Procedure
Three SKC DPM cassettes with MSA ELF pumps and one
Airtec instrument were placed in a basket 2 feet directly in
front of the canopy air curtain (CMine). Three SKC DPM
cassettes as well and one Airtec monitor were also placed in
a basket located under the DCAC, 15 inches below (to sim-
ulate the breathing zone of a male at average height) and in
the direct center (CDCAC) as shown in Figure 5. One Airtec
monitor was also placed next to the V-bank filter housing
located in the rear of the test section. This data was used to
calculate DPM loading onto the filter potentially resulting
in decreased DCAC flow.
DPM was introduced into the chamber from the
Onan diesel generator (Cummins Inc., Gibsonia, PA). A
seventy-two percent (72%) load was applied to the genera-
tor by a Simplex Swift-e plus 15-kW portable load bank
(Simplex, Springfield, IL). At this loading, the EC-to-TC
ratio approximates the composition observed in under-
ground mines (Noll et al. 2015). The generator was run for
45 minutes to stabilize the DPM concentration within the
test section. DPM stabilization was measured, during this
45-minute period, using both the Airtec and the real-time
instruments.
After the 45-minute stabilization period, the DCAC
flow was initiated. The DPM cassette pumps were started
after an additional 10-minute stabilization period and sam-
pled for 120 minutes, after which they were stopped.
The quartz filter samplers were analyzed for elemen-
tal carbon (EC) using NIOSH Method 5040 at NIOSH
Pittsburgh. EC is used as a surrogate for DPM for MSHA
sampling. The average of the three samples outside of and
under the DCAC were calculated. The percent (%)DPM
reduction due to the DCAC (EDPM, %)was calculated for
each test using equation (1):
E C
C
100
DPM
Mine
DCAC #=-^%h c1 m (1)
The percent reductions for each test were averaged, and
a standard deviation was calculated.
The ,(%)was calculated for the Airtec instrument data
by averaging the rolling averages over the time the DCAC
was running for both the instruments located under and
outside of the DCAC, then applying equation (1).
The DPM number concentration of the Experimental
Mine, not under the DCAC ,was first measured with the
APS and NanoScan and was immediately followed by
a measurement of the DPM concentration beneath the
DCAC at one of the 25 sampling points. Air sampling for
both APS and NanoScan was conducted simultaneously
for one minute by using a Y-shaped stainless-steel tube and
conductive tubing that was for splitting the airflow to the
APS and NanoScan. A total of 25 aerosol concentrations
of the Experimental Mine and 25 DPM concentrations for
each sampling point beneath DCAC were measured with
three repetitions. The DPM reduction efficiency (,%)of
the DCAC was determined by the following equation (2):
E CMine
C
100
DPM
DCAC #=-^%h c1 m (2)