(i)

Sis

Size and count only free fibres which are unattached and have

both ends visible.

When counting a field, adjust the fine focus control so that

any fibres embedded in the filter matrix are not missed.
i

Count at least one unexposed blank filter treated in the same
manner as the set of samples except that no air is drawn through
it, in order to obtain the background fibre loading ‘or the

1
samples.

The fibre counts for each sample are recorded on an. appropriate

form.
CALCULATIONS

4
Standard Sample Volumes

Use equation to determine the sample volume corrected to

standard conditions when necessary:

vV=Vv = *- 0.39 K (Vv @)
s a sreft a cos
— mm Hg
aT T
a ref a
where: v.. sample volume corrected to reference conditions, ml.
a - sample volume measured during sampling, ml.
- absolute temperature at reference conditions,
ref
760 mm Hg.
qT. - absolute temperature during sampling, ORY
P - absolute pressure at reference conditions,
ref
760 mm Hg.

P - absolute pressure during sampling, mm Hg.

Concentration of Asbestos Fibres

Use the following equation to determine the concentration of asbestos

fibres in the sample:

ss emp mri ge prt aot