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2.4.3 Manual sampling
If the internal pump option has not been chosen the hand aspirator may be used for pre-entry checks
and remote sampling. This is not however recommended for sample hoses longer than 5 meters
due to the amount of time (and therefore squeezes) it would take to get a repeatable sample to the
sensors. A water trap and lter should be used.
2.4.3.1 Using the Hand Aspirator
The hose end of the hand aspirator should be attached to the exhaust of the un-pumped ow
plate, a sensors covered warming will be shown
and the user should accept this. The bulb
should then be depressed whilst holding a nger over the inlet to ensure that a tight seal has been
achieved. The detector will at this point likely go into alarm (this is due to the pressure effect on
the oxygen sensor) and the bulb of the aspirator should not return to the rounded shape. If this
does not happen – reposition the ow plate and repeat the test. Once the test is passed allow the
O
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sensor to stabilise to 20.9% and then attach the required sample hose length to the inlet on the
ow plate and commence sampling. Depress the aspirator bulb every other second in order to get a
constant sample ow to the sensors. Every depression of the aspirator bulb should pull the sample
approximately 25cm up the tube. Therefore to sample from a 5 meter hose – at least 20 aspirations
will be required, however a minimum of 1 minute is recommended to ensure a stable sample is read.
If the Gas-Pro being used is tted with a carbon monoxide sensor (CO) a 5% increase in reading is
expected during this process due to the extra pressure placed on the sensor (ie if the sample being
tested is 30ppm – the expected result onscreen will show 32ppm.
If Gas-Pro is being used regularly for sampling, Crowcon strongly recommend the use of the internal
pumped option to reduce time and potential for error.
i
Do not use the pumped ow plate for manual sampling.
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