Gas Tracer Operator’s Manual, CSA Version
Measuring Mode, Normal Operation • 37
%LEL Sensor Relative Responses
Although the standard factory setup and calibration for the combustible gas
channel is to methane (CH
4
), the combustible sensors will respond to other
combustible gases as well.
The table below lists the conversion factors for several hydrocarbon gases for the
% LEL combustible sensor if it is calibrated to methane
. Conversion factors are
not available for the % volume TC sensor. To use this table, multiply the display
reading on the combustible gas channel by the factor in the appropriate row to
obtain the actual gas concentration. For example, if you are detecting pentane and
the display reads 10% LEL on the combustible gas channel, you actually have 10%
LEL x 1.56 = 15.6% LEL pentane present.
CO with H
2
S Response Configuration
Some applications may require the user to know if H
2
S is present while
monitoring with a Gas Tracer. The Gas Tracer does not have an H
2
S sensor
installed but if the charcoal filter is removed from the CO sensor, it will respond to
H
2
S.
Since the CO sensor cannot distinguish between CO and H
2
S, the CO channel
reading on the display could be a mix of CO and H
2
S.
If the environment you are monitoring is completely free of CO, there is an
approximate response factor that varies from sensor to sensor that can be used.
The CO sensor’s response to H
2
S is 5 times greater than the actual H
2
S
concentration. For example, if the CO channel reading is 25 ppm, the actual H
2
S
concentration is 5 ppm. This approximation is not applicable if CO is present in
the monitoring environment.
Table 3: LEL Hydrocarbon Conversions
Gas
LEL Conversion
Factor (Methane
Calibration)
Gas
LEL Conversion
Factor (Methane
Calibration)
Acetone
1.79
Iso Butane
1.47
Acetylene
1.92
MEK
2.27
Benzene
2.00
Methane
1.00
Ethane
1.09
Methanol
1.92
Ethanol
2.50
Pentane
1.56
Ethylene
1.06
Propane
1.35
Heptane
2.50
Propylene
1.32
Hexane
2.08
Toluene
3.13
Hydrogen
1.25
Xylene
4.27
IPA
2.78
