Ducting and dining

24 August 2004
Ducting and dining

Kitchen ventilation is as important a part of kitchen design and planning as cooking and refrigeration equipment. It's no longer just nice to have, but a must-have. Any new kitchen which doesn't include ventilation as a part of the design submission could be rejected by the local planning authority. And if it's installed but not properly maintained, in the event of a kitchen fire the insurance company may contest any claim. Kitchen ventilation is serious business.

Vent Master Reactocell canopy installation at the Mailbox in Birmingham
If these weren't sufficiently compelling reasons to have good ventilation in the kitchen, a new issue is beginning to emerge. The Health & Safety Executive (HSE), which is responsible for ensuring the safety of the working environment in kitchens, is growing increasingly concerned about the potentially poisonous by-products of the combustion of gas in ovens - most notably, carbon monoxide, which can cause drowsiness and inattention, and could create highly dangerous conditions in a busy kitchen. A second issue surrounding inefficient extraction of fumes and gases is that the tiny particles produced during cooking, most notably from frying and roasting, produce what the HSE describes as a deadly airborne cocktail that can cause respiratory illnesses. Any kitchen employee who is diagnosed with occupational asthma has a potential claim against the employer. Most chefs probably think that their ventilation systems meet all the requirements - but they would be wrong. The popular belief among ventilation engineers is that 65% of commercial kitchens currently have inadequate kitchen ventilation. When the former head chef of London restaurant Le Gavroche, Mark Prescott, moved back home to Lancashire three years ago to open the food-led pub the Mulberry Tree, he gave the same attention to detail to creating a safe and comfortable working environment for the kitchen team as to his choice of cooking equipment. As a result, kitchen designer Combined Catering Services installed a modular ceiling system from Vent Master, rather than the more common canopy system. This modular cell system sits almost flush to the ceiling, and lighting panels and extraction panels are fitted together. The benefit of this, says Vent Master, is that should the configuration of the kitchen be changed or the kitchen extended, the ventilation and lighting cells can be moved to new positions with the minimum of alteration to the ducting. A properly designed, installed and maintained kitchen ventilation system should last for years without any problems or hazards, except one - fire. One of the most common causes of commercial kitchen fires is the sudden combustion of grease-laden air in the extraction system, usually following a sudden flare-up on the stove. Combustion can begin in less than one second, which can be too rapid for the fire suppression system built into the canopy to respond. But this is not the worst of it. The common way to assemble ducting is to pop-rivet sections together to form a tube, but when a fire breaks out the heat can cause the rivets to melt or pop out, and then the fire can spread to other parts of the property. Fried chicken outlets are generally regarded as producing the most airborne combustible grease, but the most dangerous kitchen is one using wok cooking, where the flame in the pan is encouraged to soar upwards as part of the cooking technique. Maintenance Depending on the type of system installed, filter cleaning can be done by in-house personnel as part of routine mechanical maintenance, though the cleaning programme must be professionally drawn up. However, more advanced extraction systems must have professional cleaning. Ross Smith, a director of Bright Hygiene Management, spells out the danger of neglecting filter cleaning. "A poorly cleaned extraction system is a fuel-loaded cell above a heat source," he says. "You don't get a much worse fire hazard than that." Smith says that a problem which he regularly sees comes in the form of old ventilation systems which were adequate when installed but which cannot meet modern construction and safety standards. He says: "There is an awful lot of retro-fitting going on with older hotels, and more is needed." The frequency of cleaning ventilation ducting and filters depends on the amount of frying. A restaurant where little frying is carried out may have months between recommended cleanings, while a busy food pub could need cleaning as often as once a fortnight. A specialist ductwork cleaning company should assess the frequency required. While some metal filters can be cleaned in-house, the ducting must be professionally cleaned, and it helps to have hard evidence that a proper maintenance routine has been followed. One duct-cleaning company, the Filta Group, now offers a new proof-of-service history by using digital cameras to record evidence of good cleaning practice. While most of the heat in the kitchen goes into the food being cooked, a lot is lost into the atmosphere and goes out through the ventilation system. All heat costs money and unused heat is wasted money - that's why Calorex Heat Pumps is pushing into the commercial kitchen market with heat-extraction systems which can take the heat from the atmosphere and put it to use. The Union Caf‚ in the Marylebone district of west London has just such a calorific exchange system, extracting the heat from the kitchen and recycling it into the hot-water system, saving on energy costs and producing a better working environment. But the cash benefits of saving and recycling heat aren't restricted to the kitchen. At the Hundred House hotel in Shropshire, the air-conditioning units in the wine cellar are linked to the hot water system. By taking heat from the wine cellar, the hotel can produce 30 gallons of hot water an hour. ### Contacts CESA (Catering Equipment Suppliers Association) [www.cesa.org.uk](http://www.cesa.org.uk) CEDA (Catering Equipment Distributors Association) [www.ceda.org.uk](http://www.ceda.org.uk) Caterer Group Directory [www.caterer-online.com Calorex 01621 856611 Vent Master 01634 666111 Filta Group 01788 550100 Bright Hygiene Management 0777 846 3597 Combined Catering Services 0151-922 4454 ### Filter types Mesh filters These are layers of metal mesh on to which grease particles are deposited as they are drawn through the system. Not normally recommended for kitchens with a lot of deep-fat frying. Baffle filters More efficient than mesh filters, these work by making the air change direction and velocity, which separates the grease from the air stream. The deposited grease runs off into grease-collection troughs. Cartridge filters Stainless steel filters which are more efficient than baffle filters, being intended for moderate to heavy grease load applications. These filters can be cleaned in a dishwasher. Water wash A more advanced cartridge system in which the filters are subject to an automatic internal washing cycle to clean them, usually at the end of the working day. They need a hot water supply and are among the more expensive systems, but are very good at extracting grease. Continuous water mist A very effective means of grease extraction, but requires plumbing and can be prohibitively expensive for a smaller restaurant. A continuous mist of cold water sprayed into the extraction system emulsifies the fat and causes it to drop into a collection trough. Ultraviolet UV-C The latest technology for the efficient elimination of grease from kitchen ventilation systems is the combination of cartridge filters and ultraviolet UV-C light. This will give grease- and odour-removal efficiencies in excess of 98%.
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