What an external gas meter box is for, why its vents must stay clear, and the box faults to spot and put right.
An external meter box houses and protects the meter, regulator and emergency control valve (ECV), usually on an outside wall. It has three jobs: protection, ventilation and access.
Protection
The box and its door shield the meter, regulator and ECV from rain, sunlight, knocks and interference. That extends their life, keeps the meter readable and lets the regulator breather work in a protected space. If the door or cover is missing, the parts are exposed and can corrode or be damaged, so replace it.
Ventilation
The box is not a sealed container. Its permanent vents let a small escape, such as a weeping joint or regulator, disperse to outside air instead of building up inside the box or entering the building. Sealed or blocked vents can let that gas build up to a dangerous concentration, so keep them clear.
The vents are there to let gas disperse; they are not for combustion air or pressure relief. Ventilation is never a reason to leave a leaking fitting in service.
Sleeve and seal the installation pipe, and any cable, where it passes from the box into the building. An open route lets gas that escapes in the box track into the building or a wall cavity, where it could collect unseen. Seal these routes, never the box’s designed vents. The unsafe situations procedure classes an unsleeved or unsealed pipe route, or a damaged box, that gives gas a pathway into the building as At Risk: seal it where practical, otherwise advise the responsible person, and make sure the gas supplier is told.
Check the pressure category before treating sealing as the remedy. Where normal pressure at the regulator inlet is 75 mbar or higher, installation pipework and cables must not enter the property directly from the meter box. A sealed rear entry is still the wrong route in that arrangement.
Access
The box does not shut the gas off; the ECV inside does. So the box must never lock the occupier out of reach of it.
- The door opens easily with its key, and the key is left with the occupier.
- Nothing is stored in or packed around the box.
- The box is not hidden behind fences or planting.
Faults to spot
- vents sealed, painted over or blocked
- door or cover missing or broken
- key lost, or household items packed around the meter
- an open pipe entry through the wall