The ceiling in the new kitchen at HMP Maidstone is a state of the art construction that enables the ventilation and energy recycling systems that are based in the roof void to work.  Designed to be secure and unobtrusive it also provides an excellent working environment for the staff. It was made and installed by a company based in Leamington Spa called Britannia Kitchen Ventilation. How it achieves all this was the subject of a conversation I had with Peter Taylor, the Sales and Marketing Director

CR    What part of the ceiling, ventilation and lighting system were Britannia responsible for?
PT    Every thing visible at ceiling level in the kitchen. The unit is a large stainless steel fabrication that’s as long and wide as the main cooking area and about half a meter deep. Its job is to extract the air, remove the grease and introduce fresh air that has been filtered and matched in temperature. It also contains the lighting and essential wiring.

CR    The catering staff speaks of how the ventilation within the kitchen copes with everything they throw at it and there is always a comfortable working temperature. How did you go about designing a ceiling that can cope with the huge range of temperatures and also handle the grease contained  in the air?
PT    We are given drawings of the kitchen by the main contractor. These drawings include a detailed cooking equipment layout so we know exactly where each combi oven, boiler, fryer or hob unit will be. From this information we design the ceiling so that it has sufficient extraction capacity in exactly the right place. It is then possible to ensure that extraction of grease laden air is at its most effective where it needs to be. We also can calculate where fresh air needs to be introduced so that gas flame equipment can work effectively whilst a pleasant working environment is maintained. This is why the work environment stays so constant.

CR     So the ceiling returns air to the kitchen as well?
PT    Yes, it supplies fresh filtered air into the kitchen. It does this by having diffusers all around the perimeter of the ceiling so that the replacement air arrives at low velocity at working height without creating nuisance draughts for operatives in the kitchen. The make up air is taken from a different area to the exhausted air to prevent cross contamination and the reintroduction of combustion gasses.  Extracted air has its heat removed by the equipment in the roof void and then expelled into the atmosphere; the acquired heat is then either used to heat water or is used to heat the fresh air that is drawn into the building before it is introduced into the ceiling to be diffused into the workspace.

CR    The range of heat produced by a 6 ring burner can vary from low to very high. How do you design a ceiling so that it maintains a constant temperature 10 feet bellow it no matter what the cooking activity is? Is it computer controlled?
PT    There are not any computer controlled parts of the ceiling, there may be volume adjustable fans in the roof void that are controlled by the building management system but that is all. The plenum chambers and ducts in the roof are sized and positioned very precisely for the equipment underneath them. Were they to change around the layout or introduce more equipment then the people working in the kitchen would quickly notice a change in their working environment.

CR    How does the ceiling cope with the grease and water that is deposited in it as the extracted air passes through?
PT    The ceiling uses baffle filters within the canopy sections to extract the grease and water from the air. This is similar to the centrifugal vacuum cleaners that are on the market. The air rotates as it passes through the filter and this spins the heavy drops of grease and water to the outside where it’s deposited. And it drains to specially designed  collection trays. Before going  into the drains once treated. This eliminates the mesh filter panels that used to be common in kitchen ventilation canopies. They were not only cumbersome but they also needed cleaning every day. The baffle filters used at Maidstone are almost totally maintenance free.

CR    How adaptable or extendable is the ceiling. The kitchen at Maidstone is now at the maximum capacity for the prison population. If they wanted to extend the kitchen to increase its capacity could the ceiling be easily extended too?