LANDTEC GEM5000 - 8.8 How to use an H2 S filter (optional)

5K-MNL-GEM5000 GEM5000 Gas Analyzer
two other gases that can be found in landfill gas – hydrogen and hydrogen sulfide.
To reduce the effect of hydrogen, the GEM5000 analyzer uses a technique that is
hydrogen compensated. Hydrogen compensation is achievable up to a level of around
2000ppm. Above this level the CO reading will not be compensated for.
In order to assist the operator the GEM5000 instrument also indicates the level of
hydrogen present as low, medium or high. If a high hydrogen reading is present then
the CO reading may be affected.
The effect of hydrogen sulfide is eliminated by the use of a H2S filter.
CO measurement
The CO measurement is sensitive to hydrogen sulfide. The presence of hydrogen sulfide
can cause the CO reading to elevate (not to be the true value due to the interfering
gas). If the presence of hydrogen sulfide is suspected to be causing false CO readings,
then it is recommended that the external hydrogen sulfide filter is used while obtaining
the CO measurement.
The H2S filter only needs to be used when you are trying to remove any possible cross
gas effects H2S might have on other gas channels. Do not use the filter on all devices.
When using the H2S filter you will need to increase the gas sample and clean air purge
run-time, as using an H2S filter decreases the response time of the analyzer.
Note: There is an internal H2S filter incorporated in the chemical cell that removes
the H2S; however this has a limited life span.
The electrochemical cells used to measure H2S and CO do suffer from cross-gas effects.
Such effects are not accurately specified. However, the following table may be useful as
a guide; it represents how many ppm would be read by a cell if 100 ppm of the
interfering gas were applied, with no other cross-contaminates being present in the
sample.
GEM5000
Interfering Gas
CO
H2S
SO2
NO2
H2
Chemical
Cell
CO
(H2 compensated)
100
0 / ~300*
0
0
<1
CO
100
<4 /~300*
0
-20 to +5
<60
H2S
<4
100
20
<-25
<0.2
*after internal filter depleted.
Note: Other gases could cause cross-gas effects. If you suspect a cross
sensitivity problem please contact the Technical Support Team at
+1 (909) 783-3636.
8.8.2 Cross-gas effects on methane, carbon dioxide and oxygen
Methane is measured using dual beam infrared absorption. Analyzers are calibrated
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