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Method 7400

Asbestos and Other Fibers by PCM


This method is used for the determination of asbestos from workplace air samples.  The sample is collected cellulose ester membrane filter (MCE) and analyzed using PCM (phase contrast light microscopy).  Fibers < 0.25 µm diameter will not be detected by this method.

This method is used primarily used for estimating asbestos concentrations since PCM does not differentiate between asbestos and other fibers.  If identification of fibers is needed, NIOSH Method 7402 using electron microscopy can be used for confirmation.   This method may be used for other materials such as fibrous glass by using alternate counting rules.

The quantitative working range is 0.04 to 0.5 fiber/cc for a 1000-L air sample. The limit of detection (LOD) depends on sample volume and quantity of interfering dust, and is <0.01 fiber/cc for atmospheres free of interferences.

NOTE: This revision replaces Method 7400, Revision #3 (date 5/15/89).


(NIOSH Issue 2: 15 August 1994)

Method Data
Hold Times, Preservatives, Preps, Collection, Analytical & Documentation
Holding Time:   None specified in the method.
Preservatives:   None specified in the method.
Required Preps:   25 mm, 0.8 micron MCE filter
Collection Method:   The method recommends a 0.5-16 L/min. flow rate with a 400L sample volume.
Analytical Methodology:   PCM
Documentation:   7400


Analyte List*
Analyte
Formula
CAS Number
Detection Limit
Asbestos
1332-21-4
7
 fibers/mm˛

* The analytes and detection limits listed for each method represent the typical detection limits and analytes reported for that particular method. Keep in mind that analyte lists may vary from laboratory to laboratory. Detection limits may also vary from lab to lab and are dependent upon the sample size, matrix, and any interferences that may be present in the sample.