![]() A microscope that fails to meet these requirements has either too low or too high a resolution to be used for asbestos counting.Ĭ. Sets 4 and 5 must be at least partially visible but may vary slightly in visibility between microscopes. ![]() The requirements for asbestos counting are that the microscope optics must resolve the grooved lines in set 3 completely, although they may appear somewhat faint, and that the grooved lines in sets 6 and 7 must be invisible. 20 grooves to each block) in descending order of visibility from sets 1 to 7, seven being the least visible. Note: The slide consists of seven sets of grooved lines (ca. Bring the blocks of grooved lines into focus. Place the test slide on the microscope stage and center it under the phase objective.ī. The phase-shift detection limit of the microscope shall be about 3 degrees measured using the HSE phase shift test slide as outlined below.Ī. The microscope shall be fitted with a Walton-Beckett eyepiece graticule calibrated for a field diameter of 100 micrometers (± 2 micrometers).ġ0. The microscope shall also be fitted with a green or blue filter.ĩ. Fiber counts shall be made by positive phase contrast using a microscope with an 8 to 10 × eyepiece and a 40 to 45 × objective for a total magnification of approximately 400 × and a numerical aperture of 0.65 to 0.75. Personal samples shall be taken in the "breathing zone" of the employee (i.e., attached to or near the collar or lapel near the worker's face).Ĩ. Calibrate each personal sampling pump before and after use with a representative filter cassette installed between the pump and the calibration devices.ħ. Packing material that has a high electrostatic charge on its surface (e.g., expanded polystyrene) cannot be used because such material can cause loss of fibers to the sides of the cassette.Ħ. Ship the samples in a rigid container with sufficient packing material to prevent dislodging the collected fibers. If a filter darkens in appearance or if loose dust is seen on the filter, a second sample shall be started.ĥ. Where possible, a sufficient air volume for each air sample shall be collected to yield between 100 and 1,300 fibers per square millimeter on the membrane filter. If the 37-mm cassette is used, an air flow rate between 1 liter/min and 2.5 liters/min shall be selected.Ĥ. An air flow rate between 0.5 liter/min and 2.5 liters/min shall be selected for the 25/mm cassette. Do not reuse or reload cassettes for asbestos sample collection.ģ. The 37-mm cassette may be used if necessary but only if written justification for the need to use the 37-mm filter cassette accompanies the sample results in the employee's exposure monitoring record. The preferred collection device shall be the 25-mm diameter cassette with an open-faced 50-mm electrically conductive extension cowl. These shall be designated by the manufacturer as suitable for asbestos counting. The sampling medium for air samples shall be mixed cellulose ester filter membranes. All employers who are required to conduct air monitoring under paragraph (f) of the standard are required to utilize analytical laboratories that use this procedure, or an equivalent method, for collecting and analyzing samples.ġ. The sampling and analytical methods described below represent the elements of the available monitoring methods (such as appendix B of this regulation, the most current version of the OSHA method ID-160, or the most current version of the NIOSH Method 7400). This mandatory appendix specifies the procedure for analyzing air samples for asbestos and specifies quality control procedures that must be implemented by laboratories performing the analysis. Appendix A to § 1926.1101 - OSHA Reference Method - Mandatory
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