GasClam 2 Instrument User Manual
Ion Science Ltd.
Unrivalled Gas Detect
ion.
ionscience.com
27
400 ppm H
2
@ 20°C will read < 60 ppm
400 ppm C
2
H
2
will read < 25
Single Hydrogen Sulphide (H
2
S)
The cross sensitivities with these gases are:
•
5 ppm NO
2
will read approximately -1 ppm on the H
2
S Channel
•
50 ppm NO will read < 5 ppm on the H
2
S Channel
•
20 ppm SO
2
will read < 4 ppm on the H
2
S channel
•
400 ppm CO will read < 4 ppm on the H
2
S channel
•
10 ppm Cl
2
will read < -25 ppm on the H
2
S channel
Dual CO / H
2
S Sensor
The CO and H
2
S sensors are electrochemical sensors and suffer from cross sensitivity to other gases that may be
found in the subsurface. The carbon monoxide sensor suffers in particular from the cross sensitivity with H
2
S, H
2
and NO.
The cross sensitivities with these gases are:
•
15 ppm H
2
S will read < 6 ppm on the CO channel
•
35 ppm NO will read < 0.1 ppm on the CO channel
•
100 ppm H
2
will read approx. 20 ppm on the CO channel
The hydrogen sulphide sensor is especially cross sensitive to the following:
•
5 ppm NO
2
will read approximately -1 ppm on the H
2
S Channel
•
35 ppm NO will read < 1 ppm on the H
2
S Channel
•
5 ppm SO
2
will read < 1 ppm on the H
2
S channel
•
300 ppm CO will read < 6 ppm on the H
2
S channel
If the sensors have been exposed to gases they are cross sensitive for long periods it may take some time for the
sensors to recover. The sensors can be checked after exposure to these gases by setting the GasClam 2 to sample
every 5 minutes in clean air and the concentrations should return to zero and stabilise. If you suspect a cross
sensitivity problem please contact your supplier for further advice.
Additional CO / H
2
S sensor performance information
If the GasClam 2 is located in a zero oxygen environment for longer than 24 hours the CO and H
2
S sensor
performance may be hindered. To return the channels to optimal performance the sensor needs to be left exposed
to an oxygenated environment for the same length of time as it was deprived of oxygen for.
Above 85% RH and 40°C a maximum continuous exposure of 10 days is recommended. Where such exposure
occurs the sensor will recover normal electrolyte volumes when allowed to rest at lower % RH and temperature
for several days.
If very accurate CO or H
2
S measurements are required it is recommended that a single CO or H
2
S sensor is used.
Volatile Organic Compounds (VOC)
The VOC sensor is a mini photo ionisation detector (PID) and is sensitive to any VOCs that have an ionisation
potential less than 10.6 eV. The sensitivity of the sensor depends on the VOC present. The sensor is calibrated to
isobutylene and its response to other VOCs can be calculated using that compounds response factor. A response
