Catering kitchens

The production kitchen in an education building is a commercial kitchen within the scope of BS6173:2009. It requires the interlocking of any mechanical ventilation systems – including supply air fans – with the gas supply in the kitchen. This includes mechanical extract systems that are not over the main cooking area, but are in the same room, such as a gas-fired steamer with an extract canopy fitted above. If this steamer extract fan is not interlocked then, if it is not Figure 1: An example of a gas proving system suitable for use in a boiler plantroom Figure 2: Example of control panel that could be located adjacent to teacher’s area in laboratory CIBSE Apr15 pp23-26 CPD Supp v3.indd 24 20/03/2015 11:46 www.cibsejournal.com April 2015 CIBSE Journal 25 Turn over page to complete module switched on, air can be drawn down the steamer extract canopy along with the gas products of combustion. The air is then pulled across the occupied room by the main extract canopy. This is more likely where natural ventilation is used for make-up air.

Catering kitchens

Secondary interlocking via CO2 monitoring as part of an interlock package is not allowed in BS6173:2009, as it is considered to be an interlock override. Fixed CO2 monitoring can form part of the ventilation interlock package, as discussed in IGEM/UP/19.15 (section 5.1.2). This is to monitor the free kitchen environment, so the sensors should not be fitted under an extract canopy. For new installations, the maximum allowable level of CO2 is 2,800ppm, and for existing installations 5,000ppm. The gas supply should be isolated if the CO2 reaches these levels.

CO2 levels may also be used as an indicator of air quality in the kitchen, and can give an early indication that the ventilation is inadequate or failing – for example, due to dirty extract hood filters. IGEM/UP/19 Edition 1 Design and application of interlock devices and associated systems used in association with gas appliance installations in commercial catering establishments has recently replaced the withdrawn Gas Safe Technical Bulletin 140 (TB140).

Flame-safety devices on cooking appliances can take up to 10 seconds to close. This can result in partial, or complete, loss of gas pressure after the closure of an upstream AIV, for whatever reason.

Therefore, a gas pressure proving system can usefully form part of any interlock package, allowing for a more practical system restart to comply with the requirements of IGEM/ UP/1A Edition 2, as discussed previously. The disengagement of flexible hose bayonet connectors in kitchens can also lead to pressure loss in the distribution pipework.

Systems are now available that carry out the functions of interlocking the ventilation with gas supply, proving the gas cook line gas tightness of the appliances, as well as monitoring the carbon dioxide level in the atmosphere. Where required, such a system can also adjust the ventilation rates, depending on the amount of activity in the kitchen, by monitoring the CO2 levels and the kitchen temperature.

As long as the ventilation system has been correctly specified, then the installation of a good-quality safety and monitoring system as described will ensure comfort and maximum safety in the kitchen. Using integrated displays, these panels can provide the users with quick-reference visual indication of the state of the system, the environment, and the gas status.