AS 2985:2009 pdf free download – Workplace atmospheres—Method for sampling and gravimetric determination of respirable dust

AS 2985:2009 pdf free download – Workplace atmospheres—Method for sampling and gravimetric determination of respirable dust.
5 PRINCIPLE
Airborne concentralions of respirable dusi in the workplace are determined by passing a measured volume of air through a filter of predetermined weight. By reweighing the filter at the end of the sampling period, the weight of material collected is determined by difference.
To separate the respirable fraction, a size-selective sampler is used prior to the filter.
6 APPARATUS
6.1 Sampling systems
The essential features of a sampling system are a filter (on which the sample is collected) arid a pump for drawing the air through the filter. The filter shall be secured in a holder that prevents air from leaking around the edge of the filter. The filter shall he preceded by a size-selective sampler.
In personal sampling instruments, the filter holderfsize selector is an integral unit that is located within the worker’s breathing zone and this is connected to the pump unit (shorn on a belt or in a pocket) by flexible tubing.
6.2 Sampling de ice
The respirable fraction shall be collected by using a size-selective sampler conforming to the sampling efficiency curve, see Clause 4.7. Such devices include miniature cyclones such as the BCIRA (British Cast Iron Research Association) higgins and Dewell (see Appendix A. Reference 3) and Simpeds (Safety in Mines Research Establishment Personal Dust Sampler. Appendix A, Reference 4 and Figure 1) and aluminium cyclones (Appendix A. Reference 5) as in Table 2.
CAUTION: WHEN SAMPI.ING IN EXPLOSIVE GAS OR DUST ATMOSPHERES.
AS DEFINED IN ASN1S60079.IO.I OR ASINZS 61241.3. ENSURE THAT THE
SAMPLING PUMP MEETS THE REQUIREMENTS OF ASNZS 60079.11.
6.5 Secondary fiowmetcr
A floss meter or any secondary device such as a rotanicter or electronic flow meter shall he calibrated against the primary tlowmeter as sel out in Appendix B. The secondary t1o meter shall be used to measure the flow rate of the sampling train immediately before and after sampling. The secondar flowmeter shall he re-calibrated whenever ii is to be operated under conditions substantially different from those of the previous calibration. For example—
(a) when sampling and/or flow rate determination is conducted at an altitude differing by more than 500 m or at a temperature differing by more than 15°C from that at the previous calibration; or
(b) when experience indicates such re-calibration is necessary due to stability and maintenance history of the flowmetcr.
NOTES:
I It is generally not possible to simply calculate the different flow rates that will inevitably result from a change of conditions such as those given above.
2 Rotameters can give incorrect readings due to sticking of the float, high humidity and use in a non-vertical position, or under conditions of vibration.
3 Errors can occur using electronic flowmcter due to adverse environmental conditions.
6.6 Timing device
A stopwatch or other timing device capable of measuring elapsed time within 1% of true elapsed time.
6.7 Microbalance
6.7.1 General
A t’ive-place microbalance with a scale division of 10 tg or six-place microbalance with a scale division of I g. A standard laboratory four-place analytical balance is not suitable for this application.
6.7.2 Microhalance calibralion
The following requirements and recommendations apply:
(a) The microhalance shall be calibrated every three years, using the following principles, by either—
(i) a suitable accredited testing authority: or
(ii) competent staff employing test methods as described by Morris and Fen.
(b) Tests for departure from nominal linearity shall he conducted for at least 5 and preferably 10 points from zero up to not more than 50 or 100 mg. If the measured departure from nominal linearity exceeds the expanded uncertainty of the reference weights, the balance should he serviced, or appropriate corrections should be made.
(c) Hysteresis and, where applicable. off-centre pan loading shall he conducted using a weight in the range of 50 to 100 mg. Any hysteresis and off-centre etTects greater than the scale of the balance should be rectified by servicing, or by an appropriate change in operating procedures.