Pillar guide
Fixed Gas Detection Systems
Fixed detection continuously monitors for escaping gas and can isolate the supply automatically. Sensor technology and mounting height depend entirely on the gas being detected.
- Methane rises: mount detectors high. LPG sinks: mount low
- Two-stage alarms typically at 10% and 20% LEL
- Interlocked to a slam-shut valve for automatic isolation
System architecture
System components
- Addressable or conventional control panel with alarm relays
- Catalytic or infrared sensor heads rated for the target gas
- Sounder beacons inside and outside the risk area
- Automatic shut-off valve for isolation on high alarm
- Ventilation boost output where fitted
Placement rules
| Gas | Relative density | Detector position |
|---|---|---|
| Natural gas / methane | Lighter than air | Within 300mm of ceiling, near likely release points |
| LPG (propane/butane) | Heavier than air | Within 300mm of floor, away from drafts |
| Carbon monoxide | Similar to air | Breathing height in combustion areas |
| Carbon dioxide | Heavier than air | Low level in cellars and dispense rooms |
Servicing and calibration
Sensor heads drift and have a finite life. Annual gas-applied calibration with a certificate is expected, with catalytic heads typically replaced every three to five years and infrared heads lasting longer.
Frequently asked questions
Is gas detection a substitute for an interlock?
No. Detection responds to a release; an interlock prevents gas being supplied when ventilation is not running. Many premises need both.
How often should detection be calibrated?
At least annually with a traceable test gas, and after any alarm event or sensor replacement.
Related guides
Natural Gas Detectors
Methane sensor placement, LEL alarm levels and interlocking.
Carbon Monoxide Detection
Fixed CO monitors for boiler and plant rooms.
CO₂ Alarms
Cellar and dispense CO₂ monitoring with sounder beacons.
Plant Room Gas Detection
Boiler house detection, automatic isolation and ventilation.
Gas Safety Control Panels
Interlock and proving panels, indicators and diagnostic codes.
Gas Solenoid Valves
Normally closed automatic shut-off valves and diagnostics.
Parts in stock — ready to fit
Held in UK stock and carried on our vans, so most jobs are fixed in one visit.
Replacement gas interlock systems
Merlin, Medem, Intelligas, S&S Northern
In stock today
Air pressure switches
Fan & gas proving pressure switches
In stock today
Gas solenoid valves
Normally closed safety shut-off valves
In stock today
Quick release gas catering hoses
Commercial ranges, bays & mobile catering
In stock today
Super universal thermocouples
Fits most commercial gas appliances
In stock today
Need a part fitted?
Same-day engineer dispatch with these parts on the van.
Gas Safe Registered
Commercial catering & plant
24/7 UK Response
Same-day emergency dispatch
Vetted Engineers
DBS checked for schools & care
Transparent Pricing
Fixed callout, quoted parts