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
LPG (propane/butane) is 1.5–2.0× heavier than air and sinks to floor level. Natural gas (methane) is 0.55× the density of air and rises to ceiling level. This single fact determines detector placement.
Placement Rules
- LPG detector: 30 cm from floor
- Natural gas detector: 30 cm from ceiling
Sensor Selectivity
Gas sensors are calibrated for specific molecular targets. An LPG-calibrated sensor may not respond to methane concentrations below its calibrated threshold, even at dangerous levels.
Alarm Thresholds
Both gases share common LEL-based alarm thresholds: first alarm at 10–25% LEL, second alarm at 50% LEL. But the absolute concentration values differ significantly between LPG and methane.
Mixed Environments
In facilities using both LPG cylinders and piped natural gas, install separate detectors for each gas type at the appropriate height.
KGS Certification Implications
Korean KGS certification is gas-type specific. A KGS-certified LPG detector cannot be substituted for a natural gas detector installation under Korean regulations.