3M™ PROTÉGÉ PLUS
PORTABLE MULTI-GAS MONITOR
SENSOR K-FACTORS
8006569, Rev. C/June 2019 B-1
APPENDIX B. SENSOR K-FACTORS
Table B-1: Combustible Sensor K-Factors provides the K-Factors referenced to methane calibra-
tion. 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 correspond-
ing factor to estimate the actual gas concentration. For example, propane may be detected by the
device calibrated with methane. If the reading is 32% LEL: 32%LEL methane indicated/0.52 = 62%
LEL of propane, estimated. If the low-power catalytic sensor reads 32%LEL methane in the presence
of propane, then the concentration is estimated as: 32%LEL methane indicated/0.63 = 51%LEL pro-
pane. 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 envi-
ronment, 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 0.52 = 13%LEL). For best
accuracy, calibrate the device with a gas similar to the monitored target gas.
Table B-1: Combustible Sensor K-Factors
Known Gas Present
K-Factors
Standard
K-Factors Low Power Molecular Mass
Methane 1.00 1.00 16.0
Acetylene 0.55 0.54 26.0
n-Butane 0.45 0.69 58.1
Ethane 0.72 0.87 30.1
Hydrogen 0.70 0.87 2.0
n-Pentane 0.48 0.43 72.2
Propane 0.52 0.63 44.1
Acetone 0.53 N/A 58.1
Ethanol 0.77 N/A 46.1
Heptane 0.35 N/A 100.2
n-Hexane 0.30 N/A 86.2
Isobutanol 0.40 N/A 74.1
Isopropanol 0.39 N/A 60.1
Methanol 0.91 N/A 32.0
n-Octane 0.35 N/A 114.2
Styrene 0.31 N/A 104.2
Toluene 0.40 N/A 92.1
Xylene 0.36 N/A 106.2
NOTE: For K-Factor function setting, refer to 5.6. Sensor Information.
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