Gas Interlock Systems - Gas Proving Systems from Fleetwood Sheetmetal Kitchen Equipment

Does your commercial kitchen comply with BS6173 (2001)? What is required by law?

The British Standard BS 6173 (2001) has been amended to provide users of gas fired catering appliances (cookers, grills, ovens etc.) With protection against the effects of exposure to combustion gases given off when gas is used for cooking.

All new gas fired installations must now have a device fitted that prevents the gas from being turned on until the fume extraction system is extracting air.

The underlying principle here is that if the extract system is off, then the gas-fired cooking appliances cannot be used and therefore users cannot be put at risk.

Previously, users have been able to light the gases without first turning on the extraction system. Reasons why the user may not turn on the extraction system include "its cold in the kitchen" , "its too noisy" , "its draughty" or it may be malfunctioning and not working at all!

These changes were deemed necessary due to the possibility that a user could suffer the ill effects of a build up of these potentially dangerous fumes, which can cause headaches, nausea, fatigue and in extreme cases even worse effects.

The question posed by this change in regulations is "how do you prevent the user from inadvertently breaking the regulations which have been introduced for his/her safety?"

BS 6173 (2001) addresses this problem by requiring that an "interlock" be fitted to the gas supply system and the air extraction system.

An interlock is a device that prevents one action being taken until a certain condition is satisfied. In this case, the action is the turning on of the gas supply and the condition is that the extraction system must be switched on and working.

Gas Interlock System Operation

The operation of the gas interlock is as follows;

1. The user turns on the extraction system.

2. The airflow sensor located adjacent to the extract fan measures the air flow.

3. The sensor sends a signal to the control panel, which is mounted, in the kitchen.

4. The control panel reads the signal from the sensor, and if the air is flowing then the panel sends an electrical signal to open the gas isolation valve, thus allowing the gas to flow. The gas isolation valve isolates all the gas appliances at once, as it is located in the kitchen gas supply line.

5. If the extraction system is not on, the gas cannot flow and users cannot be at risk.

6. Should the extraction system subsequently fail, the gas will be isolated automatically.

BS 6173 (2001) now requires that "the gas supply be interlocked with any mechanical ventilation supply or extract system... No gas-fired appliance shall be fitted (or used) in a catering area if the ventilation system could adversely the safe operation of the appliance or the safe discharge of its combustion products"

Corgi guidelines are that all new installations must comply with these regulations. A system that does not comply will be issued with an "at risk" notice from the corgi approved installer. This may have insurance implications.

The regulations as they affect existing installations (pre may 2001) are a bit of a grey area. One can interpret them to mean that not only new, but existing installations should have an interlock fitted. It is difficult to argue against this interpretation on safety grounds, my understanding is that the hse are undecided about this issue. A corgi approved installer called to site to maintain an existing installation would issue a "not to current regulations" notice if one is not fitted. This may also have insurance implications.