EPA air monitoring chain of custody, Jan 2003

NYC 9/11 Public Portal Document

ASBESTOS and OTHER FIBERS by PCM: METHOD 7400, Issue 2, dated 15 August 1994 - Page 14 of 15

These rules are sometimes referred to as the "A" rules.

FIBER COUNT

Object Count DISCUSSION

1 1 fiber Optically observable asbestos fibers are actually bundles of fine fibrils. If the fibrils seem to be from the same bundle the object is counted as a single fiber. Note, however, that all objects meeting length and aspect ratio criteria are counted whether or not they appear to be asbestos.

2 2 fiber If fibers meeting the length and aspect ratio criteria (length >5 pm and length-to-width ratio >3 to 1) overlap, but do not seem to be part of the same bundle, they are counted as separate fibers.

3 1 fiber Although the object has a relatively large diameter (>3 pm), it is counted as fiber under the rules. There is no upper limit on the fiber diameter in the counting rules. Note that fiber width is measured at the widest compact section of the object.

4 1 fiber Although long fine fibrils may extend from the body of a fiber, these fibrils are considered part of the fiber if they seem to have originally been part of the bundle.

5 Do not If the object is <5 pm long, it is not counted. count

6 1 fiber A fiber partially obscured by a particle is counted as one fiber. If the fiber ends emanating from a particle do not seem to be from the same fiber and each end meets the length and aspect ratio criteria, they are counted as separate fibers.

7 1/2 fiber A fiber which crosses into the graticule area one time is counted as 1/2 fiber.

8 Do not Ignore fibers that cross the graticulate boundary more than once. count count

9 Do not Ignore fibers that lie outside the graticule boundary. count

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94

NYC-WTC_000149414