ASTM D6057-96(2011)

The SCCW may be present in the workplace atmosphere where these materials are manufactured, processed, transported, or used. This test method can be used to monitor airborne concentrations of fibers in these environments. It may be employed as part of a personal or area monitoring strategy.

This test method is based on dimensional considerations only. As such, it does not provide a positive identification of the fibers counted. Analysis by SEM or TEM is required when additional fiber identification information is needed.

Note 1—This test method assumes that the analyst is familiar with the operation of PCM instrumentation and the interpretation of data obtained using this technique.

This test method is not appropriate for measurement of fibers with diameters less than approximately 0.25 μm due to visibility limitations associated with PCM. The SEM or TEM methods may be used to provide additional size information of SCCW if needed (refer to Practice D6058 for additional information on the use of these methods).

Results from the use of this test method shall be reported along with 95 % confidence limits for the samples being studied. Individual laboratories shall determine their intralaboratory coefficient of variation and use it for reporting 95 % confidence limits (1,3,4).

1.1 This test method covers the sampling methods and analysis techniques used to assess the airborne concentration of single-crystal ceramic whiskers (SCCW), such as silicon carbide and silicon nitride, which may occur in and around the workplace where these materials are manufactured, processed, transported, or used. This test method is based on the collection of fibers by filtration of a known quantity of air through a filter. The filter is subsequently evaluated with a phase contrast microscope (PCM) for the number of fibers meeting appropriately selected counting criteria. This test method cannot distinguish among different types of fibers. This test method may be appropriate for other man-made mineral fibers (MMMF).

1.2 This test method is applicable to the quantitation of fibers on a collection filter that are greater than 5 μm in length, less than 3 μm in width, and have an aspect ratio equal to or greater than 5:1. The data are directly convertible to a statement of concentration per unit volume of air sampled. This test method is limited by the diameter of the fibers visible by PCM (typically greater than 0.25 μm in width) and the amount and type of coincident interference particles.

1.3 A more definitive analysis may be necessary to confirm the identity and dimensions of the fibers located with the PCM, especially where other fiber types may be present. Such techniques may include scanning electron microscopy (SEM) or transmission electron microscopy (TEM). The use of these test methods for the identification and size determination of SCCW is described in Practice D6058 and Test Methods D6059 and D6056.

1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.