Appendix A (Mandatory)

ASBESTOS – GENERAL INDUSTRY MANDATORY APPENDICES
Appendix A to §1910.1001—OSHA Reference Method—Mandatory
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. The sampling and analytical methods described below represent the elements of the
available monitoring methods (such as Appendix B of their regulation, the most current version of
the OSHA method ID–160, or the most current version of the NIOSH Method 7400). All
employers who are required to conduct air monitoring under paragraph (d) of the standard are
required to utilize analytical laboratories that use this procedure, or an equivalent method, for
collecting and analyzing samples.
Sampling and Analytical Procedure
1. The sampling medium for air samples shall be mixed cellulose ester filter membranes. These
shall be designated by the manufacturer as suitable for asbestos counting. See below for
rejection of blanks.
2. The preferred collection device shall be the 25-mm diameter cassette with an open-faced 50mm 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.
3. An air flow rate between 0.5 liter/min and 2.5 liters/min shall be selected for the 25-mm
cassette. If the 37-mm cassette is used, an air flow rate between 1 liter/min and 2.5 liters/min
shall be selected.
4. 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 a filter darkens in
appearance or if loose dust is seen on the filter, a second sample shall be started.
5. 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.
6. Calibrate each personal sampling pump before and after use with a representative filter
cassette installed between the pump and the calibration devices.
7. 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).
8. Fiber counts shall 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 shall also be fitted with a green or blue filter.
9. The microscope shall be fitted with a Walton-Beckett eyepiece graticule calibrated for a field
diameter of 100 micrometers (±2 micrometers).
10. The phase-shift detection limit of the microscope shall be about 3 degrees measured using
the HSE phase shift test slide as outlined below.

a. Place the test slide on the microscope stage and center it under the phase objective.
b. 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 1 to 7, seven being the least visible. 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. Sets 4 and 5 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 counting.
c. If the image deteriorates, clean and adjust the microscope optics. If the problem persists,
consult the microscope manufacturer.
11. Each set of samples taken will include 10% field blanks or a minimum of 2 field blanks. These
blanks must come from the same lot as the filters used for sample collection. The field blank
results shall be averaged and subtracted from the analytical results before reporting. A set
consists of any sample or group of samples for which an evaluation for this standard must be
made. Any samples represented by a field blank having a fiber count in excess of the detection
limit of the method being used shall be rejected.
12. The samples shall be mounted by the acetone/triacetin method or a method with an
equivalent index of refraction and similar clarity.
13. Observe the following counting rules.
a. Count only fibers equal to or longer than 5 micrometers. Measure the length of curved fibers
along the curve.
b. In the absence of other information, count all particles as asbesto that have a length-to-width
ratio (aspect ratio) of 3:1 or greater.
c. Fibers lying entirely within the boundary of the Walton-Beckett graticule field shall receive a
count of 1. Fibers crossing the boundary once, having one end within the circle, shall receive the
count of one half (1/2). 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.
d. Count bundles of fibers as one fiber unless individual fibers can be identified by observing both
ends of an individual fiber.
e. Count enough graticule fields to yield 100 fibers. Count a minimum of 20 fields; stop counting
at 100 fields regardless of fiber count.
14. Blind recounts shall be conducted at the rate of 10 percent.
Quality Control Procedures
1. Intralaboratory program. Each laboratory and/or each company with more than one
microscopist counting slides shall establish a statistically designed quality assurance program
involving blind recounts and comparisons between microscopists to monitor the variability of
counting by each microscopist and between microscopists. In a company with more than one

laboratory, the program shall include all laboratories and shall also evaluate the laboratory-tolaboratory variability.
2.a. Interlaboratory program. Each laboratory analyzing asbestos samples for compliance
determination shall implement an interlaboratory quality assurance program that as a minimum
includes participation of at least two other independent laboratories. Each laboratory shall
participate in round robin testing at least once every 6 months with at least all the other
laboratories in its interlaboratory quality assurance group. Each laboratory shall submit slides
typical of its own work load for use in this program. The round robin shall be designed and results
analyzed using appropriate statistical methodology.
2.b. All laboratories should also participate in a national sample testing scheme such as the
Proficiency Analytical Testing Program (PAT), or the Asbestos Registry sponsored by the
American Industrial Hygiene Association (AIHA).
3. All individuals performing asbestos analysis must have taken the NIOSH course for sampling
and evaluating airborne asbestos dust or an equalivalent course.
4. When the use of different microscopes contributes to differences between counters and
laboratories, the effect of the different microscope shall be evaluated and the microscope shall be
replaced, as necessary.
5. Current results of these quality assurance programs shall be posted in each laboratory to keep
the microscopists informed.