Detection
Natural Gas & Methane Detectors
Methane is lighter than air, so natural gas detectors are mounted high and close to the likely source: meter housings, boiler burners, appliance connections and riser voids.
- Ceiling-level mounting, within 300mm of the soffit
- Pre-alarm at 10% LEL, isolation at 20% LEL
- Interlocked to a slam-shut valve and sounder beacon
Sensor technology
- Catalytic bead: cost-effective, needs oxygen, poisoned by silicones
- Infrared: longer life, tolerant of poisoning, suited to plant rooms
- Semiconductor: used in low-cost fixed units, more prone to drift
Where to fit methane detectors
- Above the gas meter and pressure regulator
- Boiler room ceiling within 2m of each burner
- Kitchen ceiling adjacent to the appliance suite, outside the extract stream
- Riser cupboards and ducts carrying gas pipework
Alarm strategy
| Stage | Typical level | Output |
|---|---|---|
| Pre-alarm | 10% LEL | Local sounder, BMS alert, ventilation boost |
| High alarm | 20% LEL | Close shut-off valve, full evacuation sounders |
| Fault | Sensor open/short | Panel fault relay, engineer call-out |
Frequently asked questions
Can a domestic gas alarm be used in a commercial kitchen?
No. Commercial premises require a fixed system with fault monitoring, alarm relays and a certified calibration regime.
What does %LEL mean?
Percentage of the lower explosive limit. For methane, 100% LEL is about 4.4% gas in air, so a 20% LEL alarm triggers well below a flammable mixture.
Related guides
Gas Detection Systems
Fixed detection for methane, LPG and combustion areas.
Plant Room Gas Detection
Boiler house detection, automatic isolation and ventilation.
Carbon Monoxide Detection
Fixed CO monitors for boiler and plant rooms.
Gas Solenoid Valves
Normally closed automatic shut-off valves and diagnostics.
Gas Safety Control Panels
Interlock and proving panels, indicators and diagnostic codes.
Gas Interlock Systems
Installation, servicing, testing and fault-finding for kitchen ventilation interlocks.
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