Catering gas is a distinct competence covering commercial cooking appliances. The defining requirement is the ventilation interlock, which prevents gas being available unless extraction is proven to be running. Servicing frequency is higher than domestic because the duty cycle is far higher.
Why catering is treated separately
Commercial catering appliances differ from domestic in ways that all point the same direction. They have far higher heat inputs. They run for long continuous periods at full output. They are frequently unflued, discharging combustion products directly into the kitchen and relying on mechanical extraction to remove them. They are surrounded by staff working at speed, and by cleaning regimes that involve water and chemicals near flames and controls.
The result is a working environment where the margin for error is smaller than almost anywhere else in a commercial building, and where the failure modes – carbon monoxide accumulation, fire, gas escape – are serious and fast.
That is why commercial catering gas is a separate competence with its own appliance categories, and why the maintenance regime is more demanding than for a boiler that runs intermittently.
The ventilation interlock
This is the central control in any commercial kitchen and the thing most often found defective.
An interlock system ties the gas supply to the extraction system. If the extract and any required input ventilation are not running and proven, the interlock closes a gas safety shut-off valve and gas is not available to the appliances. It is a physical prevention, not a warning.
- Air pressure proving or airflow proving confirms that extraction is genuinely moving air, rather than that a fan has power. A fan that is running with a blocked filter or a closed damper is not extracting.
- A gas safety shut-off valve in the supply, which closes on loss of proving.
- A manual reset, so that supply is not restored automatically without somebody present.
- Emergency knock-off buttons at kitchen exits, so gas can be killed on the way out.
- Interlock with input ventilation as well as extract, because extracting air from a sealed kitchen depressurises it.
It happens – a proving switch that nuisance-trips gets jumpered out, or a valve is held open because the extraction is faulty and service must continue. The result is a kitchen where unflued appliances can run with no extraction at all. If yours has been bypassed, treat it as urgent rather than as a scheduling matter.
Ventilation in a commercial kitchen
Extraction alone is not ventilation. Air extracted must be replaced, and if it is not, the kitchen becomes negatively pressured – which starves appliances of combustion air, pulls air backwards down any flue, and makes doors difficult to open.
A properly designed kitchen has extraction sized for the appliance duty, input ventilation sized to match, and a balance between them that leaves the kitchen very slightly negative relative to the dining area so smells do not migrate, but not so negative that appliances suffer.
The common faults we find:
- Input ventilation blocked, sealed or never provided, so the kitchen runs heavily negative.
- Grease-laden filters never cleaned, so extraction rate has fallen far below design – which is a fire risk as well as a ventilation one.
- Ductwork with heavy grease accumulation, which is a serious fire risk and a specialist cleaning matter.
- Extraction canopy too small or badly positioned for the appliances actually beneath it, usually because the appliances changed and the canopy did not.
- Proving systems that have drifted out of calibration and now prove airflow that is not there.
Servicing and inspection
Catering appliances need attention more frequently than most commercial plant, because of the duty cycle and the environment.
| Item | Why it needs attention |
|---|---|
| Burners and jets | Grease, food debris and cleaning chemicals block ports and distort flame pattern |
| Flame supervision devices | The safety device that shuts off gas if a flame goes out. Degrades in a hot, greasy environment |
| Thermostats and controls | Drift in high-temperature environments, and take physical abuse |
| Hoses and quick-release couplings | Appliances are pulled out for cleaning constantly. Hoses have a finite life and restraints must be fitted |
| Combustion performance | Measured, because unflued appliances discharge directly into the room |
| Interlock system | Proven end to end, not just visually inspected |
| Canopy filters and extract | Airflow measured against design, and grease accumulation assessed |
| Isolation and emergency controls | Accessible, labelled, and actually working |
The appliance restraints deserve a note. Commercial appliances on castors are pulled out for cleaning daily, and the hose has to tolerate that. A restraint chain limits travel so the hose is never pulled taut, and it is very frequently found disconnected because it gets in the way of cleaning.
What an inspection produces
A record listing every appliance, the checks carried out, the combustion readings where applicable, the interlock test result, and the classification of any defect. That record is what your insurer will ask for, what an environmental health officer will want to see, and what a due diligence process will request if you ever sell the business.
Where a defect makes an appliance or installation unsafe, it is classified and the appliance turned off with your permission. In a working kitchen that is a commercially serious event, which is exactly why it is better to find these things on a planned visit in the morning than on a Friday night.
Kitchen interlock nuisance-tripping? That is a fault to diagnose, not a reason to bypass it. Call rather than working around it.
Questions we get asked about this
Do we legally need a gas interlock?
A ventilation interlock linking the gas supply to proven extraction is the expected arrangement in commercial catering, and it is what an inspection will look for. Its absence, or its bypassing, is a serious finding.
How often should catering appliances be serviced?
At least annually and often more frequently, driven by the duty cycle. A busy kitchen running appliances for twelve hours a day justifies more than an annual visit, and most operators find twice a year is the practical minimum.
Our interlock keeps tripping. Can it be turned off?
No. It is tripping because it is not proving airflow, which usually means blocked filters, a failed fan, a closed damper, or a proving switch out of calibration. All of those are real faults. Bypassing it leaves unflued appliances able to run with no extraction.
Who cleans the extraction ductwork?
Grease accumulation in ductwork is a specialist cleaning service, typically at a frequency driven by cooking volume and type, and your insurer may specify it. We assess the ventilation performance and will tell you when the duct is the constraint, but the cleaning itself is a specialist job.
Can a domestic gas engineer work on our kitchen?
No. Commercial catering is a separate competence with its own appliance categories. Work outside an engineer’s competence is not compliant and not insured.
What happens if an appliance fails the inspection?
It is classified according to the defect and, with your permission, turned off and labelled until rectified. We will always tell you immediately rather than at the end of the visit, so you can plan around it.
What happens when you call
Call and describe it
You speak to an engineer, not a call centre. Most jobs can be narrowed down on the phone.
We look at it properly
A real diagnosis before a price, and a straight answer if it is not worth doing.
A written quote
Itemised, so you can see what you are paying for.
The job, and the paperwork
Certificates where the work needs them, and what will need attention next.
Where we do this work
Across Norwich and the whole of Norfolk. If you are on the edge of the county, call and ask — we will tell you honestly whether we are the right people.
- Norwich
- Wymondham
- Dereham
- Attleborough
- Aylsham
- North Walsham
- Cromer
- Diss
- Loddon
- Long Stratton
- Watton
- King's Lynn
Need this doing?
Call and describe the problem — you will speak to an engineer, not a call centre. Written quotes, no estimates over the phone.