Page:NIOSH Manual of Analytical Methods - 0500.pdf/2

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PARTICULATES NOT OTHERWISE REGULATED, TOTAL: METHOD 0500, Issue 2, dated 15 August 1994 - Page 2 of 3

EQUIPMENT:

  1. Sampler: 37-mm PVC, 2- to 5-µm pore size membrane or equivalent hydrophobic filter and supporting pad in 37-mm cassette filter holder.
  2. Personal sampling pump, 1 to 2 L/min, with flexible connecting tubing.
  3. Microbalance, capable of weighing to 0.001 mg.
  4. Static neutralizer: e.g., Po-210; replace nine months after the production date.
  5. Forceps (preferably nylon).
  6. Environmental chamber or room for balance (e.g., 20 °C ± 1 °C and 50% ± 5% RH).

SPECIAL PRECAUTIONS: None.

PREPARATION OF FILTERS BEFORE SAMPLING:

  1. Equilibrate the filters in an environmentally controlled weighing area or chamber for at least 2 h.
    NOTE: An environmentally controlled chamber is desirable, but not required.
  2. Number the backup pads with a ballpoint pen and place them, numbered side down, in filter cassette bottom sections.
  3. Weigh the filters in an environmentally controlled area or chamber. Record the filter tare weight, W1 (mg).
    1. Zero the balance before each weighing.
    2. Handle the filter with forceps. Pass the filter over an antistatic radiation source. Repeat this step if filter does not release easily from the forceps or if filter attracts balance pan. Static electricity can cause erroneous weight readings.
  4. Assemble the filter in the filter cassettes and close firmly so that leakage around the filter will not occur. Place a plug in each opening of the filter cassette. Place a cellulose shrink band around the filter cassette, allow to dry and mark with the same number as the backup pad.

SAMPLING:

  1. Calibrate each personal sampling pump with a representative sampler in line.
  2. Sample at 1 to 2 L/min for a total sample volume of 7 to 133 L. Do not exceed a total filter loading of approximately 2 mg total dust. Take two to four replicate samples for each batch of field samples for quality assurance on the sampling procedure.

SAMPLE PREPARATION:

  1. Wipe dust from the external surface of the filter cassette with a moist paper towel to minimize contamination. Discard the paper towel.
  2. Remove the top and bottom plugs from the filter cassette. Equilibrate for at least 2 h in the balance room.
  3. Remove the cassette band, pry open the cassette, and remove the filter gently to avoid loss of dust.
    NOTE:If the filter adheres to the underside of the cassette top, very gently lift away by using the dull side of a scalpel blade. This must be done carefully or the filter will tear.

CALIBRATION AND QUALITY CONTROL:

  1. Zero the microbalance before all weighings. Use the same microbalance for weighing filters before and after sample collection. Maintain and calibrate the balance with National Institute of Standards and Technology Class S-1.1 or ASTM Class 1 weights.
  2. The set of replicate samples should be exposed to the same dust environment, either in a laboratory dust chamber [7] or in the field [8]. The quality control samples must be taken with the same

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition

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