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AS 2985-2009 pdf free download
AS 2985-2009 pdf free download.Workplace atmospheres-Method for sampling and gravimetric determination of respirable dust.
(vi) Recheck the balance ith a reliable reference eight at or near to the working range of the weighing filters and not greater than 50 mg.
NOTE; The difference of the reading of the reference weight to the nominal value
should be less than the limit of performance of (lie balance.
(b) During every weighing .cession When weighing filters conduct a zero check after each filter weight determination.
(c) After every weighing se.s.cion Check the calibration of the balance with the same reference weight as used previously.
NOTE: The ditTercncc of the reading of the reference weight to the nominal value should be less than the limit of performance of the balancc.
(d) Long weighing .cessions If a series of filters is being weighed the microbalancc accuracy shall be checked at appropriate intervals during the procedure.
NOTE: The difference of the reading of the reference weight to the nominal value should be less than the limit of performance of the balance.
8.2 Filter pre-weighing
The weighing procedure for filters shall be as follows:
(a) Place the fillers in individually labelled, clean containers and leave with the lids slightly ajar in the balance room for a suitable time (e.g. overnight hut this may depend on the filter type) to come to equilibrium with the balance room atmosphere. If filters that are prone to static build-tip are being used, they shall he passed over the static eliminator (Clause 6.8) to dissipate any electrostatic charge. Repeated exposure to the static eliminator with subsequent weighing shall he conducted to verify that the electrostatic charge has dissipated and is causing no weighing errors.
(b) 10% of filters (with a minimum of two) shall be selected as field blanks and submitted to the same procedures as for the sample filters with omission of the sampling step.
Weighing of blank filters shall be carried out over the same period as the sample filters.
NOTE: This may mean multiple weighing of blank filters so they are representative of changes to the sample filters due to atmospheric conditions during the weighing period. If there is a significant change of atmospheric conditions or in blank weights over the weighing session, it will he necessary to divide the sample filters into groups so that appropriate blank corrections can be applied.
(c) Weigh each sample and blank filters and record the weights. in milligrams (w1 and h1 respectively).AS 2985-2009 pdf free download.
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