Taking effective action

Published:  12 July, 2010

Works canteens kitchen ventilation systems can create significant problems for neighbours and the environment.

Complaints arising from unwanted cooking smells are especially common in densely populated urban environments. Grease, fat and other cooking residues are less obvious, but can be equally unpleasant in the urban environment.  However, works engineers may be unaware that their canteen is causing a problem until nuisance odours warrant an unwanted visit from Environmental Health.

The task of advising, approving and policing exhaust ventilation from catering outlets is shared by the Local Planning Authority in partnership with Environmental Health Officers. They act in line with Best Practice Guidance published by DEFRA in January 2005.  

Traditionally, activated carbon filters have been used as a primary method of fume and odour control in catering applications. But on its own, carbon filtration is not the best solution. The performance of carbon filters often leads to secondary issues. For example, they demand proper regular maintenance every 4-6 months and equally regular replacement with new filter cartridges, the cost of which acts as a deterrent to the maintenance, which is essential if filtration efficiencies are to be maintained. Should maintenance slip, carbon filters can have an adverse effect on back pressure and fan operation within the system, leading to noise and inefficiencies.

Best practice guidance is that a combination approach to filtration works best in most projects. Typically, this involves the use of an electronic air cleaner ahead of an activated carbon filtration system to provide the most efficient removal of fumes, odour, grease and other particulates.

The electrostatic precipitation (ESP) technology in electronic air cleaners is perfectly suited to commercial kitchen extract projects. At the heart of this approach is a high efficiency collector cell. Contaminated air is first drawn through the unit's washable metal mesh pre-filter, which traps larger airborne particles. Remaining particles, some as small as 0.01 microns, then pass into a strong electrical field within the air cleaner's ionising section, where the particulate receives an electrical charge. Charged particles then pass into the collector plate cell, which is made up of a series of equally spaced, parallel plates. Each alternate plate is charged with the same polarity as the particles, which repel, while the interleaving plates are grounded to attract and collect the particulate.

This type of electronic filtration can remove contaminants more quickly from the air than traditional carbon filters. A reduced dwell time requirement in the unit translates to more efficient performance - up to 95% sub-micron particulate can be removed at an air velocity of 3m/s. This performance, in turn, will have an impact on the design, sizing and energy efficiency of the entire system. Less power is needed because smaller extract fans can be used with smaller motors. There will also be fewer issues with sound attenuation.

The latest electronic air cleaners on the market are also modular in design, so they can cope straightforwardly with change of use situations. This versatility allows works engineers to combine collector cells with stainless steel spiked ionisers, according to the size and demand of individual kitchen hygiene applications. Unit cleaning capacities range in air volumes from 1,000 up to 17,000m3/hr respectively.  

Maintenance is another key issue with activated carbon filtration. Using an ESP type air cleaner in front of carbon will significantly reduce the cost of consumables required. ESPs themselves are quick and easy to maintain in comparison. In fact, new innovation in the sector recently introduced air cleaners that feature an automatic wash option facility.

Available as an integral control module with a number of units on the market, the wash option is custom programmed to automatically cycle the wash manifolds, detergent and exhaust fan. Specially formulated detergent is sprayed via the wash system"s manifolds to clean the plates within the electrostatic cells of the air cleaner. This allows removal of contaminants in situ, saving time and hassle. Once washing is complete, the system activates the exhaust fan to pull air across the cells and dry them before automatically switching on the power supply.

Practical experience and know-how of the issues around commercial kitchen extract ventilation counts for a great deal when searching for the right works canteen solution to nuisance problems. It is also important that engineers partner with organisations whose equipment is manufactured and tested to the required CE, ISO9001 and ASHRAE standards. For example, build tolerances and manufacturing repeatability are critical in creating the right spacing within an electronic air cleaner’s collector cell. Anything short of precision in manufacture will result in inadequate performance in the field and continued complaints. 

For further information please visit: www.trion.co.uk

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