Gas Interlock Systems are a compulsory requirement in most commercial working kitchens as they are designed to shut off the gas supply in the event of a fan failure. Commercial kitchens should have an appropriate interlocking system between the mechanical ventilation system and the operation of gas appliances in order to ensure the safe running of the kitchen. Gas Interlock Systems are also used to ensure that the air flow rates achieved by commercial kitchen extract systems meet the minimum standards set out by DW/172, the specification of kitchen ventilation systems.


    Gas interlock systems operate by monitoring the operation of the fan or fans within the ventilation system, this can be achieved by two methods:

    1. - A DIFFERENTIAL PRESSURE AIR SWITCH

    This senses the difference in air pressure either side of the fan (either intake or extract). The pressure switch can be set to different levels of sensitivity to achieve a shut off at the required level of air throughput.

    2. - AN ELECTRICAL CURRENT SENSOR

    This monitors the electrical current to the fan to achieve the same objective. Current monitors are available as a separate element, or in the case of some gas interlock control panels are built in.

    • The air pressure switch or current monitor are wired back to the gas interlock control panel, (various panels are available to suit different requirements). At their most basic, level panels monitor two fans (usually one intake and one extract), and support at least one remote emergency stop button and one gas solenoid valve. More advanced panels can support multiple intake and extract fans simultaneously, along with supporting fire alarm and shutter systems and gas proving systems (where gas equipment does not have flame failure).

      The gas interlock panel is connected to a suitably sized normally closed gas solenoid valve, this ensures that the gas supply to the kitchen is off at all times except when the kitchen extract system is operating correctly. Gas solenoid valves are available to fit most pipe sizes, however it is necessary to consider the pipe material – e.g black iron pipework has a smaller bore than measuring the pipe exterior. Where the gas interlock control panel is not located on the emergency exit it is also necessary to locate an emergency stop on the escape route.

      A 13 Amp switched spur is used to connect the system and this provides power for the gas interlock control panel. All other elements are then wired from the panel in low voltage cabling. The installation of the system should be completed by a suitable qualified electrician with the fitting of the gas solenoid valve into the pipework being undertaken by a Gas Safe Register engineer.

      For a basic system to operate on a standard commercial kitchen extract, to comply with BS6173:2009 and IGEM/UP/19 you will require a gas interlock control panel, one differential air pressure switch (two where an intake fan is also present), a correctly sized gas solenoid valve and a remote emergency stop. For a more advanced system you can use a panel with a built in current monitoring system meaning that you do not need air pressure switches.