Using an LPG detector in a natural gas environment - or vice versa - can result in missed detections. This technical guide explains why, and how to specify the right sensor for each application.
The Fundamental Difference: Density
The most critical physical difference between LPG and natural gas is their density relative to air:
This single physical property determines where your detector must be mounted. An LPG detector installed at ceiling height will never detect a leak accumulating at floor level, even as dangerous concentrations build up.
Sensor Technology and Selectivity
Most residential and commercial gas detectors use catalytic bead (pellistor) or semiconductor sensors. Both types can be calibrated for either LPG or natural gas, but they are not interchangeable without recalibration.
- Catalytic bead sensorsHighly accurate, stable over time, used in professional-grade detectors. Require calibration for target gas. Standard in KGS-certified equipment.
- Semiconductor sensorsLower cost, suitable for residential applications. Can show cross-sensitivity to other gases (alcohol, paint fumes). Calibration for target gas is still required.
- Infrared (NDIR) sensorsNot affected by poisons or humidity. Used in industrial applications. More expensive but offers high accuracy for hydrocarbon gases.
LEL Values Compared
LEL (Lower Explosive Limit) values differ between gases, which affects sensor calibration and alarm thresholds:
| Gas | LEL (%vol) | UEL (%vol) | Density vs Air |
|---|---|---|---|
| Propane (LPG) | 2.1% | 9.5% | Heavier (1.56) |
| Butane (LPG) | 1.8% | 8.4% | Heavier (2.07) |
| Methane (NG) | 5.0% | 15% | Lighter (0.55) |
| CO | 12.5% | 74% | Slightly lighter (0.97) |
Installation Placement Rules
- Mount 30cm from floor
- Avoid corners where gas pools
- Do not place behind appliances
- Minimum 1.5m from ignition sources
- Mount 30cm from ceiling
- Near gas appliances (1-4m range)
- Avoid ventilation outlets
- Away from steam and cooking vapors
Which Soosan Product is Right?
Soosan Hometech manufactures detectors calibrated for both LPG and natural gas applications. When ordering, always specify your gas type - all models are available in LPG or NG variants.
Our team can specify the right detector for your environment
Tell us your gas type, application, and target market - we'll recommend the right model and certification path.