Washington Administrative Code › Title 296 - Labor and Industries, Department of › Chapter 296-62 - General occupational health standards › Part I-1 - ASBESTOS, TREMOLITE, ANTHOPHYLLITE, AND ACTINOLITE › Section 296-62-07735 - Appendix A-WISHA reference method-Mandatory

Current through Register Vol. 24-14, July 15, 2024
This mandatory appendix specifies the procedure for analyzing
				  air samples for asbestos, tremolite, anthophyllite, and actinolite and
				  specifies quality control procedures that must be implemented by laboratories
				  performing the analysis. The sampling and analytical methods described below
				  represent the elements of the available monitoring methods (such as Appendix B
				  to this section, the most current version of the WISHA method ID-60, or the
				  most current version of the NIOSH 7400 method) which WISHA considers to be
				  essential to achieve adequate employee exposure monitoring while allowing
				  employers to use methods that are already established within their
				  organizations. All employers who are required to conduct air monitoring under
				  WAC
				  296-62-07709
				  are required to utilize analytical laboratories that use this procedure, or an
				  equivalent method, for collecting and analyzing samples.
(1)  Sampling and analytical procedure.
(a)  The sampling medium for air samples must
				be mixed cellulose ester filter membranes. These must be designated by the
				manufacturer as suitable for asbestos, tremolite, anthophyllite, and actinolite
				counting. See below for rejection of blanks.
(b)
				 The preferred collection device is the 25-mm diameter cassette
				with an open-faced 50-mm electrically conductive extension cowl. 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. Do not reuse or reload cassettes for
				asbestos sample collection.
(c)  An
				air flow rate between 0.5 liter/min and 4.0 liters/min must be selected for the
				25-mm cassette. If the 37mm cassette is used, an air flow rate between 1
				liter/min and 4.0 liters/min must be selected.
(d)  Where possible, a sufficient air volume
				for each air sample must be collected to yield between one hundred and one
				thousand three hundred fibers per square millimeter on the membrane filter. If
				a filter darkens in appearance or if loose dust is seen on the filter, a second
				sample must be started.
(e)  Ship
				the samples in a rigid container with sufficient packing material to prevent
				dislodging the collected fibers. 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.
(f)  Calibrate each personal sampling pump
				before and after use with a representative filter cassette installed between
				the pump and the calibration devices.
(g)
				 Personal samples must be taken in the "breathing zone" of the
				employee (i.e., attached to or near the collar or lapel near the worker's
				face).
(h)  Fiber counts must be
				made by positive phase contrast using a microscope with an 8 to 10 X eyepiece
				and a 40 to 45 X objective for a total magnification of approximately 400 X and
				a numerical aperture of 0.65 to 0.75. The microscope must also be fitted with a
				green or blue filter.
(i)  The
				microscope must be fitted with a Walton-Beckett eyepiece graticule calibrated
				for a field diameter of one hundred micrometers (+/-2 micrometers).
(j)  The phase-shift detection limit of the
				microscope must be about 3 degrees measured using the HSE phase shift test
				slide as outlined below.
(i)  Place the test
				slide on the microscope stage and center it under the phase
				objective.
(ii)  Bring the blocks
				of grooved lines into focus.
Note:
The slide consists of seven sets of grooved lines (ca.
						  20 grooves to each block) in descending order of visibility from sets one to
						  seven, seven being the least visible. The requirements for asbestos, tremolite,
						  anthophyllite, and actinolite counting are that the microscope optics must
						  resolve the grooved lines in set three completely, although they may appear
						  somewhat faint, and that the grooved lines in sets six and seven must be
						  invisible. Sets four and five must be at least partially visible but may vary
						  slightly in visibility between microscopes. A microscope that fails to meet
						  these requirements has either too low or too high a resolution to be used for
						  asbestos, tremolite, anthophyllite, and actinolite counting.
(iii)
				 If the image deteriorates, clean and adjust the microscope
				optics. If the problem persists, consult the microscope manufacturer.
(k)  Each set of samples taken
				will include ten percent blanks or a minimum of two blanks. These blanks must
				come from the same lot as the filters used for sample collection. The field
				blank results must be averaged and subtracted from the analytical results
				before reporting. Any samples represented by a blank having a fiber count in
				excess of the detection limit of the method being used must be
				rejected.
(l)  The samples must be
				mounted by the acetone/triacetin method or a method with an equivalent index of
				refraction and similar clarity.
(m)
				 Observe the following counting rules.
(i)
				 Count only fibers equal to or longer than five micrometers.
				Measure the length of curved fibers along the curve.
(ii)  Count all particles as asbestos,
				tremolite, anthophyllite, and actinolite that have a length-to-width ratio
				(aspect ratio) of three to one or greater.
(iii)
				 Fibers lying entirely within the boundary of the Walton-Beckett
				graticule field must receive a count of one. Fibers crossing the boundary once,
				having one end within the circle, must receive the count of one-half. Do not
				count any fiber that crosses the graticule boundary more than once. Reject and
				do not count any other fibers even though they may be visible outside the
				graticule area.
(iv)  Count bundles
				of fibers as one fiber unless individual fibers can be identified by observing
				both ends of an individual fiber.
(v)
				 Count enough graticule fields to yield 100 fibers. Count a
				minimum of 20 fields; stop counting at 100 fields regardless of fiber
				count.
(n)  Blind
				recounts must be conducted at the rate of ten percent.