Appendix B to Part 50 - Reference Method for the Determination of Suspended Particulate Matter in the Atmosphere (High-Volume Method)
40:2.0.1.1.1.0.1.20.3 : Appendix B
Appendix B to Part 50 - Reference Method for the Determination of
Suspended Particulate Matter in the Atmosphere (High-Volume Method)
1.0 Applicability.
1.1 This method provides a measurement of the mass concentration
of total suspended particulate matter (TSP) in ambient air for
determining compliance with the primary and secondary national
ambient air quality standards for particulate matter as specified
in § 50.6 and § 50.7 of this chapter. The measurement process is
nondestructive, and the size of the sample collected is usually
adequate for subsequent chemical analysis. Quality assurance
procedures and guidance are provided in part 58, appendixes A and
B, of this chapter and in References 1 and 2.
2.0 Principle.
2.1 An air sampler, properly located at the measurement site,
draws a measured quantity of ambient air into a covered housing and
through a filter during a 24-hr (nominal) sampling period. The
sampler flow rate and the geometry of the shelter favor the
collection of particles up to 25-50 µm (aerodynamic diameter),
depending on wind speed and direction.(3) The filters used
are specified to have a minimum collection efficiency of 99 percent
for 0.3 µm (DOP) particles (see Section 7.1.4).
2.2 The filter is weighed (after moisture equilibration) before
and after use to determine the net weight (mass) gain. The total
volume of air sampled, corrected to EPA standard conditions (25 °C,
760 mm Hg [101 kPa]), is determined from the measured flow rate and
the sampling time. The concentration of total suspended particulate
matter in the ambient air is computed as the mass of collected
particles divided by the volume of air sampled, corrected to
standard conditions, and is expressed in micrograms per standard
cubic meter (µg/std m 3). For samples collected at temperatures and
pressures significantly different than standard conditions, these
corrected concentrations may differ substantially from actual
concentrations (micrograms per actual cubic meter), particularly at
high elevations. The actual particulate matter concentration can be
calculated from the corrected concentration using the actual
temperature and pressure during the sampling period.
3.0 Range.
3.1 The approximate concentration range of the method is 2 to
750 µg/std m 3. The upper limit is determined by the point at which
the sampler can no longer maintain the specified flow rate due to
the increased pressure drop of the loaded filter. This point is
affected by particle size distribution, moisture content of the
collected particles, and variability from filter to filter, among
other things. The lower limit is determined by the sensitivity of
the balance (see Section 7.10) and by inherent sources of error
(see Section 6).
3.2 At wind speeds between 1.3 and 4.5 m/sec (3 and 10 mph), the
high-volume air sampler has been found to collect particles up to
25 to 50 µm, depending on wind speed and direction.(3) For
the filter specified in Section 7.1, there is effectively no lower
limit on the particle size collected.
4.0 Precision.
4.1 Based upon collaborative testing, the relative standard
deviation (coefficient of variation) for single analyst precision
(repeatability) of the method is 3.0 percent. The corresponding
value for interlaboratory precision (reproducibility) is 3.7
percent.(4)
5.0 Accuracy.
5.1 The absolute accuracy of the method is undefined because of
the complex nature of atmospheric particulate matter and the
difficulty in determining the “true” particulate matter
concentration. This method provides a measure of particulate matter
concentration suitable for the purpose specified under Section 1.0,
Applicability.
6.0 Inherent Sources of Error.
6.1 Airflow variation. The weight of material collected
on the filter represents the (integrated) sum of the product of the
instantaneous flow rate times the instantaneous particle
concentration. Therefore, dividing this weight by the average flow
rate over the sampling period yields the true particulate matter
concentration only when the flow rate is constant over the period.
The error resulting from a nonconstant flow rate depends on the
magnitude of the instantaneous changes in the flow rate and in the
particulate matter concentration. Normally, such errors are not
large, but they can be greatly reduced by equipping the sampler
with an automatic flow controlling mechanism that maintains
constant flow during the sampling period. Use of a contant flow
controller is recommended.*
*At elevated altitudes, the effectiveness of automatic flow
controllers may be reduced because of a reduction in the maximum
sampler flow.
6.2 Air volume measurement. If the flow rate changes
substantially or nonuniformly during the sampling period,
appreciable error in the estimated air volume may result from using
the average of the presampling and postsampling flow rates. Greater
air volume measurement accuracy may be achieved by (1) equipping
the sampler with a flow controlling mechanism that maintains
constant air flow during the sampling period,* (2) using a
calibrated, continuous flow rate recording device to record the
actual flow rate during the samping period and integrating the flow
rate over the period, or (3) any other means that will accurately
measure the total air volume sampled during the sampling period.
Use of a continuous flow recorder is recommended, particularly if
the sampler is not equipped with a constant flow controller.
6.3 Loss of volatiles. Volatile particles collected on
the filter may be lost during subsequent sampling or during
shipment and/or storage of the filter prior to the postsampling
weighing.(5) Although such losses are largely unavoidable,
the filter should be reweighed as soon after sampling as
practical.
6.4 Artifact particulate matter. Artifact particulate
matter can be formed on the surface of alkaline glass fiber filters
by oxidation of acid gases in the sample air, resulting in a higher
than true TSP determination.(6 7) This effect usually occurs
early in the sample period and is a function of the filter pH and
the presence of acid gases. It is generally believed to account for
only a small percentage of the filter weight gain, but the effect
may become more significant where relatively small particulate
weights are collected.
6.5 Humidity. Glass fiber filters are comparatively
insensitive to changes in relative humidity, but collected
particulate matter can be hygroscopic.(8) The moisture
conditioning procedure minimizes but may not completely eliminate
error due to moisture.
6.6 Filter handling. Careful handling of the filter
between the presampling and postsampling weighings is necessary to
avoid errors due to loss of fibers or particles from the filter. A
filter paper cartridge or cassette used to protect the filter can
minimize handling errors. (See Reference 2, Section 2).
6.7 Nonsampled particulate matter. Particulate matter may
be deposited on the filter by wind during periods when the sampler
is inoperative. (9) It is recommended that errors from this
source be minimized by an automatic mechanical device that keeps
the filter covered during nonsampling periods, or by timely
installation and retrieval of filters to minimize the nonsampling
periods prior to and following operation.
6.8 Timing errors. Samplers are normally controlled by
clock timers set to start and stop the sampler at midnight. Errors
in the nominal 1,440-min sampling period may result from a power
interruption during the sampling period or from a discrepancy
between the start or stop time recorded on the filter information
record and the actual start or stop time of the sampler. Such
discrepancies may be caused by (1) poor resolution of the timer
set-points, (2) timer error due to power interruption, (3)
missetting of the timer, or (4) timer malfunction. In general,
digital electronic timers have much better set-point resolution
than mechanical timers, but require a battery backup system to
maintain continuity of operation after a power interruption. A
continuous flow recorder or elapsed time meter provides an
indication of the sampler run-time, as well as indication of any
power interruption during the sampling period and is therefore
recommended.
6.9 Recirculation of sampler exhaust. Under stagnant wind
conditions, sampler exhaust air can be resampled. This effect does
not appear to affect the TSP measurement substantially, but may
result in increased carbon and copper in the collected sample.
(10) This problem can be reduced by ducting the exhaust air
well away, preferably downwind, from the sampler.
7.0 Apparatus.
(See References 1 and 2 for quality assurance information.)
Note:
Samplers purchased prior to the effective date of this amendment
are not subject to specifications preceded by (†).
7.1 Filter. (Filters supplied by the Environmental
Protection Agency can be assumed to meet the following criteria.
Additional specifications are required if the sample is to be
analyzed chemically.)
7.1.1 Size: 20.3 ±0.2 × 25.4 ±0.2 cm (nominal 8 × 10
in).
7.1.2 Nominal exposed area: 406.5 cm 2 (63 in 2).
7.1.3. Material: Glass fiber or other relatively inert,
nonhygroscopic material. (8)
7.1.4 Collection efficiency: 99 percent minimum as
measured by the DOP test (ASTM-2986) for particles of 0.3 µm
diameter.
7.1.5 Recommended pressure drop range: 42-54 mm Hg
(5.6-7.2 kPa) at a flow rate of 1.5 std m 3/min through the nominal
exposed area.
7.1.6 pH: 6 to 10. (11)
7.1.7 Integrity: 2.4 mg maximum weight loss.
(11)
7.1.8 Pinholes: None.
7.1.9 Tear strength: 500 g minimum for 20 mm wide strip
cut from filter in weakest dimension. (See ASTM Test D828-60).
7.1.10 Brittleness: No cracks or material separations
after single lengthwise crease.
7.2 Sampler. The air sampler shall provide means for
drawing the air sample, via reduced pressure, through the filter at
a uniform face velocity.
7.2.1 The sampler shall have suitable means to:
a. Hold and seal the filter to the sampler housing.
b. Allow the filter to be changed conveniently.
c. Preclude leaks that would cause error in the measurement of
the air volume passing through the filter.
d. (†) Manually adjust the flow rate to accommodate variations
in filter pressure drop and site line voltage and altitude. The
adjustment may be accomplished by an automatic flow controller or
by a manual flow adjustment device. Any manual adjustment device
must be designed with positive detents or other means to avoid
unintentional changes in the setting.
(†) See note at beginning of Section 7 of this appendix.
7.2.2 Minimum sample flow rate, heavily loaded filter:
1.1 m 3/min (39 ft 3/min).‡
‡ These specifications are in actual air volume units; to
convert to EPA standard air volume units, multiply the
specifications by (Pb/Pstd)(298/T) where Pb and T are the
barometric pressure in mm Hg (or kPa) and the temperature in K at
the sampler, and Pstd is 760 mm Hg (or 101 kPa).
7.2.3 Maximum sample flow rate, clean filter: 1.7 m 3/min
(60 ft 3/min).‡
7.2.4 Blower Motor: The motor must be capable of
continuous operation for 24-hr periods.
7.3 Sampler shelter.
7.3.1 The sampler shelter shall:
a. Maintain the filter in a horizontal position at least 1 m
above the sampler supporting surface so that sample air is drawn
downward through the filter.
b. Be rectangular in shape with a gabled roof, similar to the
design shown in Figure 1.
c. Cover and protect the filter and sampler from precipitation
and other weather.
d. Discharge exhaust air at least 40 cm from the sample air
inlet.
e. Be designed to minimize the collection of dust from the
supporting surface by incorporating a baffle between the exhaust
outlet and the supporting surface.
7.3.2 The sampler cover or roof shall overhang the sampler
housing somewhat, as shown in Figure 1, and shall be mounted so as
to form an air inlet gap between the cover and the sampler housing
walls. † This sample air inlet should be approximately uniform on
all sides of the sampler. † The area of the sample air inlet must
be sized to provide an effective particle capture air velocity of
between 20 and 35 cm/sec at the recommended operational flow rate.
The capture velocity is the sample air flow rate divided by the
inlet area measured in a horizontal plane at the lower edge of the
cover. † Ideally, the inlet area and operational flow rate should
be selected to obtain a capture air velocity of 25 ±2 cm/sec.
7.4 Flow rate measurement devices.
7.4.1 The sampler shall incorporate a flow rate measurement
device capable of indicating the total sampler flow rate. Two
common types of flow indicators covered in the calibration
procedure are (1) an electronic mass flowmeter and (2) an orifice
or orifices located in the sample air stream together with a
suitable pressure indicator such as a manometer, or aneroid
pressure gauge. A pressure recorder may be used with an orifice to
provide a continuous record of the flow. Other types of flow
indicators (including rotameters) having comparable precision and
accuracy are also acceptable.
7.4.2 † The flow rate measurement device must be capable of
being calibrated and read in units corresponding to a flow rate
which is readable to the nearest 0.02 std m 3/min over the range
1.0 to 1.8 std m 3/min.
7.5 Thermometer, to indicate the approximate air
temperature at the flow rate measurement orifice, when temperature
corrections are used.
7.5.1 Range: −40° to + 50 °C (223-323 K).
7.5.2 Resolution: 2 °C (2 K).
7.6 Barometer, to indicate barometric pressure at the
flow rate measurement orifice, when pressure corrections are
used.
7.6.1 Range: 500 to 800 mm Hg (66-106 kPa).
7.6.2 Resolution: ±5 mm Hg (0.67 kPa).
7.7 Timing/control device.
7.7.1 The timing device must be capable of starting and stopping
the sampler to obtain an elapsed run-time of 24 hr ±1 hr (1,440 ±60
min).
7.7.2 Accuracy of time setting: ±30 min, or better. (See
Section 6.8).
7.8 Flow rate transfer standard, traceable to a primary
standard. (See Section 9.2.)
7.8.1 Approximate range: 1.0 to 1.8 m 3/min.
7.8.2 Resolution: 0.02 m 3/min.
7.8.3 Reproducibility: ±2 percent (2 times coefficient of
variation) over normal ranges of ambient temperature and pressure
for the stated flow rate range. (See Reference 2, Section 2.)
7.8.4 Maximum pressure drop at 1.7 std m 3/min; 50 cm H2
O (5 kPa).
7.8.5 The flow rate transfer standard must connect without leaks
to the inlet of the sampler and measure the flow rate of the total
air sample.
7.8.6 The flow rate transfer standard must include a means to
vary the sampler flow rate over the range of 1.0 to 1.8 m 3/min
(35-64 ft 3/min) by introducing various levels of flow resistance
between the sampler and the transfer standard inlet.
7.8.7 The conventional type of flow transfer standard consists
of: An orifice unit with adapter that connects to the inlet of the
sampler, a manometer or other device to measure orifice pressure
drop, a means to vary the flow through the sampler unit, a
thermometer to measure the ambient temperature, and a barometer to
measure ambient pressure. Two such devices are shown in Figures 2a
and 2b. Figure 2a shows multiple fixed resistance plates, which
necessitate disassembly of the unit each time the flow resistance
is changed. A preferable design, illustrated in Figure 2b, has a
variable flow restriction that can be adjusted externally without
disassembly of the unit. Use of a conventional, orifice-type
transfer standard is assumed in the calibration procedure (Section
9). However, the use of other types of transfer standards meeting
the above specifications, such as the one shown in Figure 2c, may
be approved; see the note following Section 9.1.
7.9 Filter conditioning environment
7.9.1 Controlled temperature: between 15° and 30 °C with
less than ±3 °C variation during equilibration period.
7.9.2 Controlled humidity: Less than 50 percent relative
humidity, constant within ±5 percent.
7.10 Analytical balance.
7.10.1 Sensitivity: 0.1 mg.
7.10.2 Weighing chamber designed to accept an unfolded 20.3 ×
25.4 cm (8 × 10 in) filter.
7.11 Area light source, similar to X-ray film viewer, to
backlight filters for visual inspection.
7.12 Numbering device, capable of printing identification
numbers on the filters before they are placed in the filter
conditioning environment, if not numbered by the supplier.
8.0 Procedure.
(See References 1 and 2 for quality assurance information.)
8.1 Number each filter, if not already numbered, near its edge
with a unique identification number.
8.2 Backlight each filter and inspect for pinholes, particles,
and other imperfections; filters with visible imperfections must
not be used.
8.3 Equilibrate each filter in the conditioning environment for
at least 24-hr.
8.4 Following equilibration, weigh each filter to the nearest
milligram and record this tare weight (Wi) with the filter
identification number.
8.5 Do not bend or fold the filter before collection of the
sample.
8.6 Open the shelter and install a numbered, preweighed filter
in the sampler, following the sampler manufacturer's instructions.
During inclement weather, precautions must be taken while changing
filters to prevent damage to the clean filter and loss of sample
from or damage to the exposed filter. Filter cassettes that can be
loaded and unloaded in the laboratory may be used to minimize this
problem (See Section 6.6).
8.7 Close the shelter and run the sampler for at least 5 min to
establish run-temperature conditions.
8.8 Record the flow indicator reading and, if needed, the
barometric pressure (P 33) and the ambient temperature (T 33) see
NOTE following step 8.12). Stop the sampler. Determine the sampler
flow rate (see Section 10.1); if it is outside the acceptable range
(1.1 to 1.7 m 3/min [39-60 ft 3/min]), use a different filter, or
adjust the sampler flow rate. Warning: Substantial flow adjustments
may affect the calibration of the orifice-type flow indicators and
may necessitate recalibration.
8.9 Record the sampler identification information (filter
number, site location or identification number, sample date, and
starting time).
8.10 Set the timer to start and stop the sampler such that the
sampler runs 24-hrs, from midnight to midnight (local time).
8.11 As soon as practical following the sampling period, run the
sampler for at least 5 min to again establish run-temperature
conditions.
8.12 Record the flow indicator reading and, if needed, the
barometric pressure (P 33) and the ambient temperature (T 33).
Note:
No onsite pressure or temperature measurements are necessary if
the sampler flow indicator does not require pressure or temperature
corrections (e.g., a mass flowmeter) or if average barometric
pressure and seasonal average temperature for the site are
incorporated into the sampler calibration (see step 9.3.9). For
individual pressure and temperature corrections, the ambient
pressure and temperature can be obtained by onsite measurements or
from a nearby weather station. Barometric pressure readings
obtained from airports must be station pressure, not corrected to
sea level, and may need to be corrected for differences in
elevation between the sampler site and the airport. For samplers
having flow recorders but not constant flow controllers, the
average temperature and pressure at the site during the sampling
period should be estimated from weather bureau or other
available data.
8.13 Stop the sampler and carefully remove the filter, following
the sampler manufacturer's instructions. Touch only the outer edges
of the filter. See the precautions in step 8.6.
8.14 Fold the filter in half lengthwise so that only surfaces
with collected particulate matter are in contact and place it in
the filter holder (glassine envelope or manila folder).
8.15 Record the ending time or elapsed time on the filter
information record, either from the stop set-point time, from an
elapsed time indicator, or from a continuous flow record. The
sample period must be 1,440 ±60 min. for a valid sample.
8.16 Record on the filter information record any other factors,
such as meteorological conditions, construction activity, fires or
dust storms, etc., that might be pertinent to the measurement. If
the sample is known to be defective, void it at this time.
8.17 Equilibrate the exposed filter in the conditioning
environment for at least 24-hrs.
8.18 Immediately after equilibration, reweigh the filter to the
nearest milligram and record the gross weight with the filter
identification number. See Section 10 for TSP concentration
calculations.
9.0 Calibration.
9.1 Calibration of the high volume sampler's flow indicating or
control device is necessary to establish traceability of the field
measurement to a primary standard via a flow rate transfer
standard. Figure 3a illustrates the certification of the flow rate
transfer standard and Figure 3b illustrates its use in calibrating
a sampler flow indicator. Determination of the corrected flow rate
from the sampler flow indicator, illustrated in Figure 3c, is
addressed in Section 10.1
Note:
The following calibration procedure applies to a conventional
orifice-type flow transfer standard and an orifice-type flow
indicator in the sampler (the most common types). For samplers
using a pressure recorder having a square-root scale, 3 other
acceptable calibration procedures are provided in Reference 12.
Other types of transfer standards may be used if the manufacturer
or user provides an appropriately modified calibration procedure
that has been approved by EPA under Section 2.8 of appendix C to
part 58 of this chapter.
9.2 Certification of the flow rate transfer standard.
9.2.1 Equipment required: Positive displacement standard
volume meter traceable to the National Bureau of Standards (such as
a Roots meter or equivalent), stop-watch, manometer, thermometer,
and barometer.
9.2.2 Connect the flow rate transfer standard to the inlet of
the standard volume meter. Connect the manometer to measure the
pressure at the inlet of the standard volume meter. Connect the
orifice manometer to the pressure tap on the transfer standard.
Connect a high-volume air pump (such as a high-volume sampler
blower) to the outlet side of the standard volume meter. See Figure
3a.
9.2.3 Check for leaks by temporarily clamping both manometer
lines (to avoid fluid loss) and blocking the orifice with a
large-diameter rubber stopper, wide cellophane tape, or other
suitable means. Start the high-volume air pump and note any change
in the standard volume meter reading. The reading should remain
constant. If the reading changes, locate any leaks by listening for
a whistling sound and/or retightening all connections, making sure
that all gaskets are properly installed.
9.2.4 After satisfactorily completing the leak check as
described above, unclamp both manometer lines and zero both
manometers.
9.2.5 Achieve the appropriate flow rate through the system,
either by means of the variable flow resistance in the transfer
standard or by varying the voltage to the air pump. (Use of
resistance plates as shown in Figure 1a is discouraged because the
above leak check must be repeated each time a new resistance plate
is installed.) At least five different but constant flow rates,
evenly distributed, with at least three in the specified flow rate
interval (1.1 to 1.7 m 3/min [39-60 ft 3/min]), are required.
9.2.6 Measure and record the certification data on a form
similar to the one illustrated in Figure 4 according to the
following steps.
9.2.7 Observe the barometric pressure and record as P1 (item 8
in Figure 4).
9.2.8 Read the ambient temperature in the vicinity of the
standard volume meter and record it as T1 (item 9 in Figure 4).
9.2.9 Start the blower motor, adjust the flow, and allow the
system to run for at least 1 min for a constant motor speed to be
attained.
9.2.10 Observe the standard volume meter reading and
simultaneously start a stopwatch. Record the initial meter reading
(Vi) in column 1 of Figure 4.
9.2.11 Maintain this constant flow rate until at least 3 m 3 of
air have passed through the standard volume meter. Record the
standard volume meter inlet pressure manometer reading as ΔP
(column 5 in Figure 4), and the orifice manometer reading as ΔH
(column 7 in Figure 4). Be sure to indicate the correct units of
measurement.
9.2.12 After at least 3 m 3 of air have passed through the
system, observe the standard volume meter reading while
simultaneously stopping the stopwatch. Record the final meter
reading (Vf) in column 2 and the elapsed time (t) in column 3 of
Figure 4.
9.2.13 Calculate the volume measured by the standard volume
meter at meter conditions of temperature and pressures as Vm =
Vf−Vi. Record in column 4 of Figure 4.
9.2.14 Correct this volume to standard volume (std m 3) as
follows:
where: Vstd = standard volume, std m 3; Vm =
actual volume measured by the standard volume meter; P1 =
barometric pressure during calibration, mm Hg or kPa; ΔP =
differential pressure at inlet to volume meter, mm Hg or kPa; Pstd
= 760 mm Hg or 101 kPa; Tstd = 298 K; T1 = ambient temperature
during calibration, K. Calculate the standard flow rate (std m
3/min) as follows:
where: Qstd = standard
volumetric flow rate, std m 3/min t = elapsed time, minutes.
Record Qstd to the nearest 0.01 std m 3/min in column 6 of
Figure 4.
9.2.15 Repeat steps 9.2.9 through 9.2.14 for at least four
additional constant flow rates, evenly spaced over the approximate
range of 1.0 to 1.8 std m 3/min (35-64 ft 3/min).
9.2.16 For each flow, compute
√ΔΔH (P1/Pstd)(298/T1) (column 7a of Figure 4) and plot these value
against Qstd as shown in Figure 3a. Be sure to use consistent units
(mm Hg or kPa) for barometric pressure. Draw the orifice transfer
standard certification curve or calculate the linear least squares
slope (m) and intercept (b) of the certification curve: √ΔΔH
(P1/Pstd)(298/T1) = mQstd + b. See Figures 3 and 4. A certification
graph should be readable to 0.02 std m 3/min.
9.2.17 Recalibrate the transfer standard annually or as required
by applicable quality control procedures. (See Reference 2.)
9.3 Calibration of sampler flow indicator.
Note:
For samplers equipped with a flow controlling device, the flow
controller must be disabled to allow flow changes during
calibration of the sampler's flow indicator, or the alternate
calibration of the flow controller given in 9.4 may be used. For
samplers using an orifice-type flow indicator downstream of the
motor, do not vary the flow rate by adjusting the voltage or power
supplied to the sampler.
9.3.1 A form similar to the one illustrated in Figure 5 should
be used to record the calibration data.
9.3.2 Connect the transfer standard to the inlet of the sampler.
Connect the orifice manometer to the orifice pressure tap, as
illustrated in Figure 3b. Make sure there are no leaks between the
orifice unit and the sampler.
9.3.3 Operate the sampler for at least 5 minutes to establish
thermal equilibrium prior to the calibration.
9.3.4 Measure and record the ambient temperature, T2, and the
barometric pressure, P2, during calibration.
9.3.5 Adjust the variable resistance or, if applicable, insert
the appropriate resistance plate (or no plate) to achieve the
desired flow rate.
9.3.6 Let the sampler run for at least 2 min to re-establish the
run-temperature conditions. Read and record the pressure drop
across the orifice (ΔH) and the sampler flow rate indication (I) in
the appropriate columns of Figure 5.
9.3.7 Calculate √ΔΔH(P2/Pstd)(298/T2) and determine the flow
rate at standard conditions (Qstd) either graphically from the
certification curve or by calculating Qstd from the least square
slope and intercept of the transfer standard's transposed
certification curve: Qstd = 1/m √ΔH(P2/Pstd)(298/T2)−b. Record the
value of Qstd on Figure 5.
9.3.8 Repeat steps 9.3.5, 9.3.6, and 9.3.7 for several
additional flow rates distributed over a range that includes 1.1 to
1.7 std m 3/min.
9.3.9 Determine the calibration curve by plotting values of the
appropriate expression involving I, selected from table 1, against
Qstd. The choice of expression from table 1 depends on the flow
rate measurement device used (see Section 7.4.1) and also on
whether the calibration curve is to incorporate geographic average
barometric pressure (Pa) and seasonal average temperature (Ta) for
the site to approximate actual pressure and temperature. Where Pa
and Ta can be determined for a site for a seasonal period such that
the actual barometric pressure and temperature at the site do not
vary by more than ±60 mm Hg (8 kPa) from Pa or ±15 °C from Ta,
respectively, then using Pa and Ta avoids the need for subsequent
pressure and temperature calculation when the sampler is used. The
geographic average barometric pressure (Pa) may be estimated from
an altitude-pressure table or by making an (approximate) elevation
correction of −26 mm Hg (−3.46 kPa) for each 305 m (1,000 ft) above
sea level (760 mm Hg or 101 kPa). The seasonal average temperature
(Ta) may be estimated from weather station or other records. Be
sure to use consistent units (mm Hg or kPa) for barometric
pressure.
9.3.10 Draw the sampler calibration curve or calculate the
linear least squares slope (m), intercept (b), and correlation
coefficient of the calibration curve: [Expression from table 1]=
mQstd + b. See Figures 3 and 5. Calibration curves should be
readable to 0.02 std m 3/min.
9.3.11 For a sampler equipped with a flow controller, the flow
controlling mechanism should be re-enabled and set to a flow near
the lower flow limit to allow maximum control range. The sample
flow rate should be verified at this time with a clean filter
installed. Then add two or more filters to the sampler to see if
the flow controller maintains a constant flow; this is particularly
important at high altitudes where the range of the flow controller
may be reduced.
9.4 Alternate calibration of flow-controlled samplers. A
flow-controlled sampler may be calibrated solely at its controlled
flow rate, provided that previous operating history of the sampler
demonstrates that the flow rate is stable and reliable. In this
case, the flow indicator may remain uncalibrated but should be used
to indicate any relative change between initial and final flows,
and the sampler should be recalibrated more often to minimize
potential loss of samples because of controller malfunction.
9.4.1 Set the flow controller for a flow near the lower limit of
the flow range to allow maximum control range.
9.4.2 Install a clean filter in the sampler and carry out steps
9.3.2, 9.3.3, 9.3.4, 9.3.6, and 9.3.7.
9.4.3 Following calibration, add one or two additional clean
filters to the sampler, reconnect the transfer standard, and
operate the sampler to verify that the controller maintains the
same calibrated flow rate; this is particularly important at high
altitudes where the flow control range may be reduced.
10.0 Calculations of TSP Concentration.
10.1 Determine the average sampler flow rate during the sampling
period according to either 10.1.1 or 10.1.2 below.
10.1.1 For a sampler without a continuous flow recorder,
determine the appropriate expression to be used from table 2
corresponding to the one from table 1 used in step 9.3.9. Using
this appropriate expression, determine Qstd for the initial flow
rate from the sampler calibration curve, either graphically or from
the transposed regression equation:
Qstd = 1/m ([Appropriate expression from table 2]−b) Similarly,
determine Qstd from the final flow reading, and calculate the
average flow Qstd as one-half the sum of the initial and final flow
rates.
10.1.2 For a sampler with a continuous flow recorder, determine
the average flow rate device reading, I, for the period. Determine
the appropriate expression from table 2 corresponding to the one
from table 1 used in step 9.3.9. Then using this expression and the
average flow rate reading, determine Qstd from the sampler
calibration curve, either graphically or from the transposed
regression equation:
Qstd = 1/m ([Appropriate expression from table 2]−b)
If the trace shows substantial flow change during the sampling
period, greater accuracy may be achieved by dividing the sampling
period into intervals and calculating an average reading before
determining Qstd.
10.2 Calculate the total air volume sampled as:
V − Qstd × t where: V = total air volume sampled, in standard
volume units, std m 3/; Qstd = average standard flow rate, std m
3/min; t = sampling time, min.
10.3 Calculate and report the particulate matter concentration
as:
where: TSP = mass concentration of total
suspended particulate matter, µg/std m 3; Wi = initial weight of
clean filter, g; Wf = final weight of exposed filter, g; V = air
volume sampled, converted to standard conditions, std m 3, 10 6 =
conversion of g to µg.
10.4 If desired, the actual particulate matter concentration
(see Section 2.2) can be calculated as follows:
(TSP)a = TSP (P3/Pstd)(298/T3) where: (TSP)a = actual concentration
at field conditions, µg/m 3; TSP = concentration at standard
conditions, µg/std m 3; P3 = average barometric pressure during
sampling period, mm Hg; Pstd = 760 mn Hg (or 101 kPa); T3 = average
ambient temperature during sampling period, K.
11.0 References.
1. Quality Assurance Handbook for Air Pollution Measurement
Systems, Volume I, Principles. EPA-600/9-76-005, U.S. Environmental
Protection Agency, Research Triangle Park, NC 27711, 1976.
2. Quality Assurance Handbook for Air Pollution Measurement
Systems, Volume II, Ambient Air Specific Methods.
EPA-600/4-77-027a, U.S. Environmental Protection Agency, Research
Triangle Park, NC 27711, 1977.
3. Wedding, J. B., A. R. McFarland, and J. E. Cernak. Large
Particle Collection Characteristics of Ambient Aerosol Samplers.
Environ. Sci. Technol. 11:387-390, 1977.
4. McKee, H. C., et al. Collaborative Testing of Methods to
Measure Air Pollutants, I. The High-Volume Method for Suspended
Particulate Matter. J. Air Poll. Cont. Assoc., 22 (342), 1972.
5. Clement, R. E., and F. W. Karasek. Sample Composition Changes
in Sampling and Analysis of Organic Compounds in Aerosols. The
Intern. J. Environ. Anal. Chem., 7:109, 1979.
6. Lee, R. E., Jr., and J. Wagman. A Sampling Anomaly in the
Determination of Atmospheric Sulfuric Concentration. Am. Ind.
Hygiene Assoc. J., 27:266, 1966.
7. Appel, B. R., et al. Interference Effects in Sampling
Particulate Nitrate in Ambient Air. Atmospheric Environment,
13:319, 1979.
8. Tierney, G. P., and W. D. Conner. Hygroscopic Effects on
Weight Determinations of Particulates Collected on Glass-Fiber
Filters. Am. Ind. Hygiene Assoc. J., 28:363, 1967.
9. Chahal, H. S., and D. J. Romano. High-Volume Sampling Effect
of Windborne Particulate Matter Deposited During Idle Periods. J.
Air Poll. Cont. Assoc., Vol. 26 (885), 1976.
10. Patterson, R. K. Aerosol Contamination from High-Volume
Sampler Exhaust. J. Air Poll. Cont. Assoc., Vol. 30 (169),
1980.
11. EPA Test Procedures for Determining pH and Integrity of
High-Volume Air Filters. QAD/M-80.01. Available from the Methods
Standardization Branch, Quality Assurance Division, Environmental
Monitoring Systems Laboratory (MD-77), U.S. Environmental
Protection Agency, Research Triangle Park, NC 27711, 1980.
12. Smith, F., P. S. Wohlschlegel, R. S. C. Rogers, and D. J.
Mulligan. Investigation of Flow Rate Calibration Procedures
Associated with the High-Volume Method for Determination of
Suspended Particulates. EPA-600/4-78-047, U.S. Environmental
Protection Agency, Research Triangle Park, NC, June 1978.
[47 FR 54912, Dec.
6, 1982; 48 FR 17355, Apr. 22, 1983]