LEL Sensor Relative Response
| Relative Response of a Flammable/Combustible Sensor |
| Combustible gas / vapor | Relative response when sensor is calibrated on pentane | Relative response when sensor is calibrated on propane | Relative response when sensor is calibrated on methane |
| Hydrogen | 2.2 | 1.7 | 1.1 |
| Methane | 2.0 | 1.5 | 1.0 |
| Propane | 1.3 | 1.0 | 0.65 |
| n-Butane | 1.2 | 0.9 | 0.6 |
| n-Pentane | 1.0 | 0.75 | 0.5 |
| n-Hexane | 0.9 | 0.7 | 0.45 |
| n-Octane | 0.8 | 0.6 | 0.4 |
| Methanol | 2.3 | 1.75 | 1.15 |
| Ethanol | 1.6 | 1.2 | 0.8 |
| Isopropyl Alcohol | 1.4 | 1.05 | 0.7 |
| Acetone | 1.4 | 1.05 | 0.7 |
| Ammonia | 2.6 | 2.0 | 1.3 |
| Toluene | 0.7 | 0.5 | 0.35 |
| Gasoline(Unleaded) | 1.2 | 0.9 | 0.6 |
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 pentane | Correction factor when sensor is calibrated on propane | Correction factor when sensor is calibrated on methane |
| Hydrogen | 0.45 | 0.59 | 0.9 |
| Methane | 0.5 | 0.67 | 1.0 |
| Propane | 0.77 | 1.0 | 0.54 |
| n-Butane | 0.83 | 1.12 | 1.67 |
| n-Pentane | 1.0 | 1.34 | 2.0 |
| n-Hexane | 1.11 | 1.43 | 2.23 |
| n-Octane | 1.25 | 1.67 | 2.5 |
| Methanol | 0.44 | 0.57 | 0.87 |
| Ethanol | 0.63 | 0.84 | 1.25 |
| Isopropyl Alcohol | 0.71 | 0.95 | 1.43 |
| Acetone | 0.71 | 0.95 | 1.43 |
| Ammonia | 0.39 | 0.5 | 0.77 |
| Toluene | 1.43 | 2.0 | 2.86 |
| Gasoline(Unleaded) | 0.84 | 1.12 | 1.67 |
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
