Installation HiVol 3000 User manual 1.7
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2.4.2 Exhaust connections
A 50mm PVC flap valve is provided to prevent wind blowing back
through the pipes when the blower motor is not running. This
prevents the filter paper being disturbed during non-sampling
periods.
It is recommended that the sampler be operated with approximately
3m of exhaust tubing. The exhaust tubing prevents recycling of
filtered air, and also assists in the reduction of noise.
A suitable exhaust duct may be constructed with a 50 mm BSP
female connector, two 90° PVC elbows and 3.5m of 50 mm PVC
tubing. The flap valve can be installed on the end of the duct. An
alternative is to use a flexible hose attached to the HiVol with a 50
mm BSP female connector.
2.4.3 Muffler for noise reduction
An external muffler is available as an option. It may be connected to
the exhaust outlet. The exhaust should then be ducted away from the
sampler as described above.
2.4.4 Filter Selection for TSP sampling
High volume filter media are available from a number of
commercial suppliers. The choice will be dependent upon the
specific analytical requirement on the collected particulate matter.
The most commonly employed filter medium is glass fibre.
However, quartz and teflon-coated glass fibre filters are widely used
because they are less prone to artefact formation than the standard
glass fibre filters. Glass fibre filters being alkaline can react with
acid gases in the atmosphere to form artefact sulphate and nitrate
compounds on the filter.
It is important that the filter medium selected is capable of
maintaining a flow rate of at least 1.0m
3
/min at all times throughout
a typical 24 hour sampling period.
The minimum collection efficiency must be 99 percent as
determined by the DOP test (ASTM-2986) for particles of 0.3 µm
diameter.
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