Current through Register 2022 Notice Reg. No. 16, April 25, 2022
Air Sampling and Analytical Procedures for Determining
Concentrations of Cotton Dust
I.SAMPLING LOCATIONS
The sampling procedures must be designed so that
samples of the actual dust concentrations are collected accurately and
consistently and reflect the concentrations of dust at the place and time of
sampling. Sufficient number of 6-hour area samples in each distinct work area
of the plant should be collected at locations which provide representative
samples of air to which the worker is exposed. In order to avoid filter
overloading, sampling time may be shortened when sampling in dusty areas.
Samples in each work area should be gathered simultaneously or sequentially
during a normal operating period. The daily time-weighted average (TWA)
exposure of each worker can then be determined by using the following
formula:
Image 1 (3.57" X 1.63") Available for Offline
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(T1C1+T2C2....+TnCn), |
| TWA= |
_________________ |
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Total Hours Exposed |
where:
T sub1,T sub2 Tn=the number of hours spent in a given
location;
and
C sub1,C sub2 Cn=the dust concentration in the same
location.
A time-weighted average concentration should be
computed for each worker and properly logged and maintained on file for
review.
II.SAMPLING
EQUIPMENT
A.Sampler:
The instrument selected for monitoring is the
Lumsden-Lynch vertical elutriator. It should operate at a flow rate of 7.4 plus
or minus 0.2 liters/minute.
The samplers should be cleaned prior to sampling. The
pumps should be monitored during sampling.
B.Filter Holder:
A three-piece cassette constructed of polystyrene
designed to hold a 37 mm diameter filter should be used. Care must be exercised
to assure that an adequate seal exists between elements of the cassette.
C.Filters and Support Pads:
The membrane filters used should be polyvinyl chloride
with a 5- m m pore size and 37 mm diameter. A support pad, commonly called a
backup pad, should be used under the filter membrane in the field monitor
cassette.
D.Balance:
A balance sensitive to 10 micrograms should be
used.
III.INSTRUMENT CALIBRATION PROCEDURE
Samplers shall be calibrated when first received from
the factory, after repair, and after receiving any abuse. The samplers should
be calibrated in the laboratory both before they are used in the field and
after they have been used to collect a large number of field samples. The
primary standard, such as a wet test meter, should be used. Instructions of
calibration with the wet test meter follow. If another calibration device is
selected, equivalent procedures should be used:
(a) Level wet test meter. Check the water
level which should just touch the calibration point at the left side of the
meter. If water level is low, add water 1-2 degrees F warmer than room
temperature to the fill point. Run the meter for 30 minutes before calibration;
(b) Place the polyvinyl chloride
membrane filter in the filter cassette;
(c) Assemble the calibration sampling train;
(d) Connect the wet test meter to
the train. The pointer on the meter should run clockwise and a pressure drop of
not more than 1.0 inch of water indicated. If the pressure drop is greater than
1.0 inch, disconnect and check the system;
(e) Operate the system for ten minutes before
starting the calibration;
(f)
Check the vacuum gauge on the pump to assure that the pressure drop across the
orifice exceeds 17 inches of mercury;
(g) Record the following on calibration data
sheets;
(1) Wet test meter reading, start and
finish;
(2) Elapsed time, start
and finish (at least two minutes);
(3) Pressure drop at manometer;
(4) Air temperature;
(5) Barometric pressure; and
(6) Limiting orifice number;
(h) Calculate the flow rate and
compare against the flow of 7.4 plus or minus 0.2 liters/minute. If flow is
between these limits perform calibration again, average results, and record
orifice number and flow rate. If flow is not within these limits, discard or
modify orifice and repeat procedure.
(i) Record the name of the person performing
the calibration, the date, serial number of the wet test meter, and the number
of the critical orifices being calibrated.
IV.SAMPLING PROCEDURE
A.Sampling data sheets should include a log
of:
1.The date of the sample collection;
2.The time of sampling;
3.The location of the sampler;
4.The sampler serial number;
5.The cassette number;
6.The time of starting and stopping the
sampling and the duration of sampling;
7.The weight of the filter before and after
sampling;
8.The weight of the dust
collected (corrected for controls);
9.The dust concentration measured;
10.Other pertinent information; and
11.Name of person taking sample;
B.Assembly of filter
cassette should be as follows:
1.Loosely
assemble 3-piece cassette;
2.Number cassette;
3.Place absorbent pad in cassette;
4.Weigh filter to an accuracy of 10 m g;
5.Place filter in cassette;
6.Record weight of filter in log,
using cassette number for identification;
7.Fully assemble cassette, using pressure to
force parts tightly together;
8.Install plugs top and bottom;
9.Put shrink band on cassette, covering joint
between center and bottom parts of cassette; and
10.Set cassette aside until shrink band dries
thoroughly.
C.Sampling
collection should be performed as follows:
1.Clean lint out of the motor and elutriator;
2.Install vertical elutriator in
sampling locations with inlet 4 1/2 to 5 1/2 feet from floor (breathing zone
height);
3.Remove top section of
cassette;
4.Install cassette in
ferrule of elutriator;
5.Tape
cassette to ferrule with masking tape or similar material for air-tight seal;
6.Remove bottom plug of cassette
and attach hose containing critical orifice;
7.Start elutriator pump and check to see if
gauge reads above 17 inches of Hg vacuum;
8.Record starting time, cassette number, and
sampler number;
9.At end of
sampling period, stop pump and record time;
10.Controls with each batch of samples
collected; two additional filter cassettes should be subjected to exactly the
same handling as the samples, except that they are not opened. These control
filters should be weighted in the same manner as the sample filters.
Any difference in weight in the control filters would
indicate that the procedure for handling sample filters may not be adequate and
should be evaluated to ascertain the cause of the difference, whether and what
necessary corrections must be made, and whether additional samples must be
collected.
D.Shipping:
The cassette with samples should be collected along
with the appropriate number of blanks, and shipped to the analytical laboratory
in a suitable container to prevent damage in transit.
E.Weighing of the sample should be achieved
as follows:
1.Remove shrink band;
2.Remove top and middle sections of the
cassette and bottom plug;
3.Remove
filter from cassette and weigh to an accuracy of 10 m g; and
4.Record weight in log against original
weight.
F.Calculation
of volume of air sampled should be determined as follows:
1.From starting and stopping times of
sampling period, determine length of time in minutes of sampling period;
2.Multiply sampling time in
minutes by flow rate of critical orifices in liters per minute divide by 1000
to find air quality in cubic meters.
G.Calculation of dust concentrations should
be made as follows:
1.Subtract weight of
clean filter from dirty filter and apply control correction to find actual
weight of sample. Record this weight (in m g) in log; and
2.Divide mass of sample in ug by air volume
in cubic meters to find dust concentration in m
g/m3. Record in log.
