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Current affairs


Level of grease production


Low Medium High Typical example


No significant production of grease laden aerosols during normal daily food production operations


Moderate production of grease laden aerosols during normal daily food production operations


Heavy significant or continual production of grease laden aerosols during normal daily food production operations


only arm access is possible), and either side of any internal equipment such as fans and attenuators and at changes of direction. The access doors should be as large as possible,


given the size and style of ductwork used. TR19 provides a table of recommended sizes. Probably the most important factor however is the frequency of cleaning of the extract system. It is not uncommon to find protocols in place for


an annual clean of the system which, depending on the frequency, type and duration of cooking is likely to be entirely inadequate. The table above shows the cleaning frequencies (in months) described in TR19. Of course, the frequency of cleaning of the


ductwork is only one factor in maintaining the cleanliness of the system. RC44 provides additional guidance in support recommending that: •


Daily usage <6


hours 12


12 6 12 6 3


6-12 hours


12-16 hours


6 4 3 >16


hours 6


3 2


ignition of combustible materials in close proximity. Recommendations in DW172 make direct reference to this risk, stating: ‘If a fire originates in or is transferred to the ductwork system, then it may spread beyond its original location ... the ductwork route shall therefore take account of this risk, have a minimum separation of 500mm between uninsulated ductwork and any combustible material.’ Whilst this guidance pertains more specifically


to the design and installation of a system, good standards of housekeeping around the ductwork, in areas like risers or roof voids, must also be observed to minimise the potential for ignition and fire spread. It should also be recognised that despite the


the insides of all filter housing and grease collection trays should be cleaned weekly


• where removable filters are fitted, they should only be removed when the system has been shut down, to prevent unfiltered air entering the ducts – these filters may be put in a dishwasher or hand washed to remove grease


• cartridge filters having integral grease collection reservoirs should be cleaned at least twice a week


• an extract plenum behind filters is part of the design, and grease collected in this area should be removed by regular cleaning at least twice a week


It also highlights the ineffectiveness of creating so called ‘fire breaks’ by cleaning small areas around access panels. Cleaning methodologies also vary, from the most common hand wipe/scrape, through to steam cleaning and high pressure water washing. Chemicals may of course be used. It is important to ensure that the method of cleaning is appropriate for the type and layout of the extract system and type of grease deposits that have built up. Often the ventilation duct will run through several


floors, touching the structure of the building in a number of places, which creates a potential risk of


presence of fire suppression systems in the canopy and ductwork, this does not negate the need or reduce the requirement for thorough extract cleaning at regular intervals. Indeed, the design and siting of suppression system pipework and heads can impact significantly on the ability to clean effectively if poorly sited. Work is currently underway at BAFE to develop


a scheme for designers, installers and maintainers of kitchen fire suppression systems, to help address these problems.


Continued concern


Despite the presence of design and cleaning guidance, it was noted that the prevalence of fire in extract systems continued to cause concern, and hence in order to raise standards, a more robust approach was required. In response, RISCAuthority approached the Building Research Establishment (BRE) with a view to establishing a certification scheme through the Loss Prevention Certification Board for kitchen extract ductwork cleaning. The result of this liaison was the publication of LPS 2084, Requirements for the LPCB approval and listing of companies carrying out inspection, cleaning and maintenance of ductwork systems. The standard includes specific requirements for the inspection and cleaning


50 DECEMBER 2017/JANUARY 2018 www.frmjournal.com


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