Commercial kitchen gas interlocks: how they work and why they trip

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If your commercial kitchen cooks on gas under a mechanical extract canopy, the gas supply to the cooking appliances is very likely interlocked with the ventilation. When the interlock trips, the gas goes off, often in the middle of service. That is frustrating, but it usually means the system is doing its job. This guide explains how a commercial kitchen gas interlock works, why interlocks trip, why bypassing one is dangerous, and what to record when it happens. It is written for owners, managers, head chefs and facilities teams, and it is based on HSE catering guidance and the IGEM standard for catering interlocks.

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Commercial heating tips and advice · 5 October 2026 · Fast Commercial Boiler Help, Gas Safe 985448

What a kitchen gas interlock is for

HSE's information sheet CAIS23 (Gas safety in catering and hospitality) explains that cooking generates products of combustion and heat, and that the ventilation system keeps these within safe environmental limits. It warns: "If a mechanical system fails or is not working correctly, the environment may become unsafe or unfit for work."

That is why CAIS23 says the installer should have fitted an appropriate interlocking system between any mechanical ventilation system and the operation of the gas appliances, "so that failure of the ventilation system causes the gas supply to the appliances to be shut off." HSE's companion sheet CAIS10 (Ventilation in catering kitchens) adds that a lack of adequate make-up air for gas-fired appliances "can lead to an accumulation of combustion products, such as carbon monoxide." Where extraction serves as the flue for a flued (type B) appliance, CAIS10 says it is considered a flue and needs an appropriate interlocking system connecting the airflow to the gas supply.

How a commercial kitchen gas interlock works

The current industry standard is IGEM/UP/19 Edition 2, published in July 2022. IGEM says it was developed with Gas Safe Register and the catering industry, and that it replaces Gas Safe Register Technical Bulletin 140. It sets requirements for "the design and application of various air flow and air quality interlock devices and associated systems used in conjunction with gas appliance installations in new commercial catering establishments." In broad terms, there are three kinds of protection you may find in a kitchen:

Air flow interlocks link the gas supply to the mechanical ventilation, so that if the ventilation fails, the gas to the appliances is shut off (the arrangement CAIS23 describes).
Air quality interlocks respond to the condition of the kitchen air itself. IGEM/UP/19 also sets requirements for air quality testing of new and existing commercial catering establishments, and notes that, where appropriate, regular ventilation checks for CO₂ levels need to be performed to maintain safety.
Carbon monoxide or carbon dioxide alarm systems. CAIS23 says that, where installed, they should give an audible alarm and be interlocked to the gas pipework serving the catering appliances with an automatic gas shut-off system. This "should be a fail-safe arrangement and requires manual intervention to restore the gas supply." CAIS23 also says domestic CO alarms are not normally suitable for commercial kitchens and should not be used.

CAIS23 is clear that alarms "are only warning devices". The primary safeguards remain an adequate and effective ventilation system and regular maintenance and servicing of all equipment by competent people. The exact design of an interlock (its sensors, control panel, gas valve and restart sequence) varies between systems and manufacturers. That is why staff should be trained on the panel fitted in your kitchen and should use only its normal user controls, as set out in the manufacturer's instructions.

Which kitchens the standard applies to

IGEM describes commercial catering establishments as those preparing meals for the public other than in domestic situations. According to its published scope, IGEM/UP/19:

applies to new commercial catering establishments, and to the replacement of, or extension to, existing installations;
is not retrospective, but recommends that existing installations be modified to meet it when appropriate, and says it would be reasonable to treat a major refurbishment as a new installation;
does not apply to mobile catering or transportable temporary event catering installations.

IGEM also notes that using mechanical ventilation "will generally require the fitting of associated interlocks to ensure the safety of staff in respect of the air quality of their working environment."

For older kitchens, CAIS23 says there are large numbers of installations that do not comply with BS 6173 or the law. BS 6173 is not retrospective, but CAIS23 says "do not be complacent". Where there is no interlocking of the ventilation system and the gas supply, you should assess whether a risk is likely to arise and, if so, make sure it is prevented or controlled. CAIS10 says the decision about interlocking should be based on a competent person's assessment of the risks of using the gas appliances.

What raises and lowers the risk

CAIS23 lists factors that increase the risk, including:

evidence that the ventilation system is not used or is unreliable;
a small room volume and poor general ventilation;
obviously poor design or maintenance of the ventilation (long, convoluted ducts, broken fans, leaking ductwork, visible escape of cooking fumes or steam);
a lack of user awareness of the effect of using gas appliances without adequate ventilation;
extensive use of gas appliances for long periods without a correctly functioning ventilation system;
an ageing system or installation, and a lack of routine or planned maintenance.

Factors that reduce the risk include good natural ventilation, a well-maintained and modern ventilation system, an appropriate ventilation system interlock, good user awareness with proper documented procedures for using the ventilation system, and "clear, permanent notices warning that appliances must not be used without the ventilation system in operation."

Why kitchen gas interlocks trip

Most trips mean the interlock has detected what it was designed to detect: ventilation that is not running or not working correctly, or an air quality or alarm condition. Typical situations include:

the extract or supply fan was not switched on before the gas appliances were used, or was switched off while they were running;
a fan has stopped or is underperforming, or the ductwork is damaged or leaking (CAIS23 gives these as signs of poor design or maintenance);
a build-up of grease and poor cleaning. CAIS23 says "effective preventative maintenance and cleaning will help to prevent appliances from regular nuisance shutdown due to the ventilation system failing", and that ductwork should be cleaned regularly because the task "is often skimped";
a CO or CO₂ alarm has activated and the automatic shut-off has closed the gas supply;
a fault in the interlock system itself, which only a competent engineer should diagnose.

Why bypassing an interlock is dangerous

CAIS23 states plainly: "Installation of manual bypasses to such interlock systems is not permitted." A bypassed interlock lets gas appliances keep burning without the ventilation that removes combustion products, which is exactly the situation CAIS10 warns can lead to carbon monoxide building up. The same sheet reminds employees that, under the Health and Safety at Work etc Act 1974, they have a duty "not to interfere with anything provided for health and safety reasons."

When a Gas Safe engineer finds factors that increase the risk, such as evidence that the ventilation system is not used or is unreliable, CAIS23 says an At Risk (AR) or Immediately Dangerous (ID) classification may be applied. In either case the advice will be not to use the appliance or installation. For AR, the engineer will ask permission to turn it off; for ID, to disconnect it. Never bypass, override, link out or disable an interlock, and don't let anyone else do it, however busy service is. If someone offers a "temporary bypass", refuse and call a Gas Safe registered engineer.

What staff can and cannot do when the interlock trips

Normal user control only. If the panel shows that the ventilation was simply not running, staff who have been trained on the system may restart it using the normal user controls and start-up sequence in the manufacturer's instructions. Nothing more.
Alarm, gas smell or unexplained trip: leave the gas off. Do not try to restore the gas after a CO or CO₂ alarm, if anyone smells gas, or if you don't know why it tripped. HSE's advice for employers is that if you suspect a leak, turn off the supply and immediately phone the National Gas Emergency Service on 0800 111 999 (natural gas) or your LPG supplier, and evacuate if in doubt. Do not turn a gas supply back on until a leak has been dealt with by a competent person.
Repeat trips: stop resetting. If it trips again after a normal restart, or keeps tripping, leave it off and get it checked. CAIS23 says anyone with concerns about the safety of their installation should not wait until the next routine maintenance visit or breakdown, but seek urgent advice from a competent gas engineer and, where necessary, a ventilation expert.
Never open the control panel, change settings, swap or cover sensors, or wedge, link out or bypass any part of the system.

What to log when a gas interlock trips

A short, consistent record helps the engineer find the cause and shows that the trip was handled properly. We suggest noting:

Record	What to note
Date and time	When it tripped, and whether it was during a busy period
What was running	Which gas appliances were in use, and whether the extract and supply fans were on
What the panel showed	Any indicator lights or fault message (a photo helps)
Alarms	Whether a CO or CO₂ alarm sounded
What people noticed	Any gas smell, fumes not clearing, excess heat, or staff feeling unwell
Action taken	A normal user restart (who did it and when) or gas left off and an engineer called
Recent work	Filter or duct cleaning, electrical work, or new or moved equipment
Pattern	Whether it has happened before, and how often

CAIS10 says that keeping records of design criteria, commissioning performance, maintenance requirements and of tests and inspections "will enable maintenance, modification and testing against the original specification." CAIS23 adds that a properly designed system with a record of its design performance makes it much easier for owners, caterers and gas engineers to assess whether the ventilation suits the cooking load. Keep the trip log with your gas safety and ventilation maintenance records.

Duty holder checklist for kitchen gas safety

Maintain gas equipment in a safe condition. Regulation 35 of the Gas Safety (Installation and Use) Regulations 1998 requires every employer or self-employed person to ensure that "any gas appliance, installation pipework or flue installed at any place of work under his control is maintained in a safe condition so as to prevent risk of injury to any person." CAIS23 says the frequency of inspection and servicing should follow the manufacturer's recommendations but "as a general rule, annual inspections are a reasonable minimum frequency, with repairs carried out as necessary."
Use the right engineer. HSE says that in workplaces such as shops, restaurants, schools and hospitals, work on gas fittings must be carried out by a Gas Safe registered engineer who is qualified to do the work, and it is your responsibility to check this. The Gas Safe ID card shows the type of work an engineer is qualified to do. In premises where the 1998 Regulations do not apply, such as canteens in factories, CAIS23 says employers must ensure staff doing gas work are competent, and Gas Safe registration is the clearest way of demonstrating that.
Keep the interlock and ventilation working. HSE's employer guidance for commercial plant says to make sure the gas supply is interlocked with the ventilation of the appliance. CAIS10 says mechanical ventilation should be maintained in efficient working order in line with the manufacturer's or installer's instructions.
Train staff. CAIS23 says staff who use gas equipment should be trained in how to use it and in visual checks for obvious faults, such as damaged pipework and connections, inoperative flame supervision devices and smells of escaping gas, and should know what to do in those situations.
Procedures and notices. Have documented procedures for using the ventilation system and permanent notices stating that appliances must not be used without the ventilation running.
Responsibility stays with the employer. IGEM/UP/19 states that "the primary responsibility for compliance with legal duties rests with the employer."

Where Fast Commercial Boiler Help fits

We work on heating and hot water plant in commercial premises: boilers, water heaters, calorifiers and plant rooms. We do not repair commercial kitchen cooking appliances. For kitchen appliances and kitchen interlock panels, use a Gas Safe registered engineer whose ID card shows the relevant catering qualifications.

The same principle applies in boiler rooms, and many plant rooms have a gas interlock that shuts off the gas if the mechanical ventilation fails. Our commercial gas safety inspection includes gas interlock and ventilation proving checks where a system is fitted, and fault-finding of nuisance tripping on heating plant. For hotels, pubs and restaurants that need hot water and heating plant looked after, see our hospitality page, or read more about our commercial gas engineers.

Safety note

Under the Gas Safety (Installation and Use) Regulations 1998, gas work must be carried out by a Gas Safe registered engineer, and we apply that rule on every site. Don't attempt DIY work on gas appliances, burners, flues or safety devices. On pressure systems, trained site staff should stick to visual and gauge checks, log the readings and report anything abnormal. Never adjust, cap, plug or test-lift a relief valve yourself.

Talk to a Gas Safe commercial engineer

Fast Commercial Boiler Help is a Gas Safe registered (985448) commercial heating business based at 4 Market Hill, Clare, Sudbury, Suffolk CO10 8NN. Our team of over 10 local engineers covers East Anglia and East London, working on commercial boilers, plant rooms, water heaters, and warm air, radiant and unit heaters. We work on commercial premises only.

Call 0800 0996 007

Call or WhatsApp 07947 578332 (a photo of the appliance data plate or the fault display helps) · Email [email protected]

Frequently asked questions

How does a commercial kitchen gas interlock work?

It links the gas supply for the cooking appliances to the mechanical ventilation, so that if the ventilation fails, the gas to the appliances is shut off (HSE CAIS23). IGEM/UP/19 Edition 2 covers both air flow and air quality interlock devices. Where CO or CO2 alarm systems are installed, CAIS23 says they should be interlocked to an automatic, fail-safe gas shut-off that needs manual intervention to restore the supply.

Why does my kitchen gas interlock keep tripping?

Usually because the ventilation is not running or not working correctly, or because an alarm has activated. CAIS23 notes that effective preventative maintenance and cleaning help to prevent nuisance shutdowns caused by the ventilation failing. Repeated trips need a competent gas engineer and, where necessary, a ventilation specialist. Don't keep resetting it.

Is it legal to bypass a gas interlock in a commercial kitchen?

No. HSE CAIS23 says installation of manual bypasses to these interlock systems is not permitted, and it reminds employees of their duty under the Health and Safety at Work etc Act 1974 not to interfere with anything provided for health and safety reasons. A bypass lets gas appliances run without the ventilation that removes combustion products, including carbon monoxide.

Can kitchen staff reset a gas interlock?

Only by using the normal user controls in the manufacturer's instructions, as they have been trained, for example once the ventilation has been restarted. Do not restore the gas after a CO or CO2 alarm, a gas smell or an unexplained trip, and never open the panel or alter the system. Gas work must be carried out by a Gas Safe registered engineer under the Gas Safety (Installation and Use) Regulations 1998.

Do existing commercial kitchens need a gas interlock?

IGEM/UP/19 is not retrospective, but it applies to replacements and extensions and recommends upgrading existing installations when appropriate. HSE CAIS23 says that where there is no interlocking of the ventilation and gas supply, you should assess whether a risk is likely to arise and prevent or control it. CAIS10 says the decision should be based on a competent person's risk assessment.

Sources and further reading

Call 0800 0996 007

Call or WhatsApp 07947 578332 · [email protected]

General guidance only. This article is general information for commercial premises. It is not a substitute for advice from a competent engineer who has seen your site and equipment, or for the manufacturer's instructions. Duty holders remain responsible for their own legal compliance.