Protégé Portable Gas Monitor
Instruction Manual
61 of 61
P/N 087-0038 Rev. J 02/10
Appendix
Combustible Sensor K-Factors
The table lists K-factors referenced to methane calibration. The factors are the typical ratios of the
response to the listed gases relative to the response to methane. The values are typical, but will
vary from sensor to sensor and over the lifetime of a given sensor. When a gas other than the
calibration gas is detected, divide the reading by the corresponding factor to estimate the actual gas
concentration. For example, propane may be detected by a Protégé calibrated with methane. If the
reading is 32% LEL: 32% LEL Methane indicated/0.65 = 49% LEL of propane, estimated. Generally,
if there is a potential for methane in the operating environment, the instrument should be calibrated
with methane. If there also is a potential for other gases in the operating environment, the LEL alarm
level should be adjusted according to the lowest K-factor of the expected gases. For example, if
either methane or propane may be present, and the desired alarm is 25% LEL, calibrate the
instrument with methane and set the alarm level at (25% x 0.65 = 16% LEL). For best accuracy,
calibrate the Protégé with a gas similar to the monitored target gas.
Known Gas Present K-Factor
n-Butane 0.6
Methanol 1.04
Ethane 0.8
Hydrogen 1.1
Methane 1
Propane 0.65
n-Pentane 0.5
n-Hexane 0.45
n-Octane 0.4
Ethanol 0.8
Isopropanol 0.69
Acetone 0.7
Ammonia 1.3
Toluene 0.35
Gasoline 0.6
Isobutanol 0.53
Xylene 0.49
Styrene 0.46
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