Methods for the determination of the hazardous properties - TSAR

ECB/TM/26 rev.7
1.4.4.2.2 1.4.4.2.2 FIBRE AND PARTICULATE NUMBER (fibres/cm 3 ) AND BIVARIATE SIZE DISTRIBUTION (µm)
BY SCANNING ELECTRON MICROSCOPY (SEM)
These should be sampled at least twice per day. These samples should be taken in timely coincidence with
the gravimetric sampling with sample duration dependent upon fibre type (usually less than 30 minutes).
One filter per day should be analysed for fibre and particulate number, with the remaining filters used if
anomalies are found. Bivariate analysis of diameter and length should be determined at least twice weekly
with the additional filters used if anomalies are found. Fibre concentration should be expressed as total
number of fibres/cm 3 and the number of fibres/cm 3 with length > 20 µm, 5-20 µm, < 5 µm and WHO
fibres and the number of particles/cm 3 .
1.4.4.2.3 CHEMICAL ANALYSIS
One filter sample should be taken for possible analysis.
1.4.4.3 Counting and Sizing Rules (for aerosol and lung fibres)
The general guidelines provided by the WHO/EURO (reference (1)) are recommended with the following
additional procedures for mineral fibres (due to the possibility of smaller diameters, additional procedures
may be required for natural or organic fibres).
1.4.4.3.1 LENGTH AND DIAMETER
Sizing of length and diameters should be performed using a SEM at a magnification of at least 2000. All
objects which are seen at this magnification are to be counted. Fibres crossing the boundary of the field of
view should be counted as follows. Fibres with only one end in the field are weighted as half of a fibre
and fibres with neither of their ends in the field are not measured. Diameters of fibres which are seen at
2000 magnification should be measured at ‘full screen’ magnification (usually up to a magnification of
10,000). No lower or upper limit is to be imposed on either length or diameter. For bulk fibres with mean
diameters below a few tenths of a micrometer, an initial magnification of at least 5000 should be used.
The length and diameter are to be recorded individually for each fibre measured so that the bivariate
distribution can be determined. When sizing, an object is to be accepted as a fibre if the ratio of length to
diameter was at least 3:1. All other objects are considered particles. There should be no truncation in the
measurements. If fibre measurements are made using SEM photomicrographs or video prints where the
magnification of the photo or print is at least twice that of the SEM screen, then an initial SEM
magnification of at least 1000 is acceptable, providing fibres of 0.1 µm diameter can be resolved. When
using photomicrographs or video prints, higher magnifications should be used for diameter measurement
than for length measurement in order to ensure good precision.
1.4.4.3.2 STOPPING RULES
Enough fields of view are to be counted for evaluation so that at least a total of 0.15 mm 2 of the filter
surface (for 25 mm diameter) is examined. Once this condition is fulfilled:
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