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LEL Sensor Relative Response and LEL Sensor Correction Factors

LEL Sensor Relative Response

Relative Response of a Flammable/Combustible Sensor
Combustible gas / vapor Relative response when sensor is calibrated on pentaneRelative response when sensor is calibrated on propaneRelative response when sensor is calibrated on methane
Hydrogen 2.21.71.1
Methane 2.01.51.0
Propane 1.31.00.65
n-Butane 1.20.90.6
n-Pentane 1.00.750.5
n-Hexane 0.90.70.45
n-Octane 0.80.60.4
Methanol 2.31.751.15
Ethanol 1.61.20.8
Isopropyl Alcohol 1.41.050.7
Acetone 1.41.050.7
Ammonia 2.62.01.3
Toluene 0.70.50.35
Gasoline(Unleaded) 1.20.90.6

Correction Factors

  • The correction factor is the reciprocal of the relative response
  • Consider a detector calibrated on methane, then used to monitor ethanol
  • When calibrated on methane, the sensor shows a relative response to ethanol of 0.8
  • In other words, the readings will be 20% lower than actual
  • The correction factor would be calculated as: 1 / 0.8 = 1.25

LEL Sensor Correction Factors

Correction Factor of a Flammable/Combustible Sensor
Combustible gas / vapor Correction factor when sensor is calibrated on pentaneCorrection factor when sensor is calibrated on propaneCorrection factor when sensor is calibrated on methane
Hydrogen 0.450.590.9
Methane 0.50.671.0
Propane 0.771.00.54
n-Butane 0.831.121.67
n-Pentane 1.01.342.0
n-Hexane 1.111.432.23
n-Octane 1.251.672.5
Methanol 0.440.570.87
Ethanol 0.630.841.25
Isopropyl Alcohol 0.710.951.43
Acetone 0.710.951.43
Ammonia 0.390.50.77
Toluene 1.432.02.86
Gasoline(Unleaded) 0.841.121.67

Correction Factors

  • Multiplying the instrument reading by the correction factor for ethanol provides the true concentration
  • Given a correction factor for ethanol of 1.25, and an instrument reading of 40 per cent LEL, the true concentration would be calculated as:

40 % LEL
Instrument Reading
x 1.25
Correction Factor
= 50 % LEL
True Concentration