FIRE SAFETY


n The Environmental Protection Act of 1990 allows the government to take legal action against commercial kitchens if they are judged to pose a nuisance through the discharge of grease, smoke, or odour. This needs to be taken into account by system specifiers.


n The Occupiers Liability Act 1984 requires a duty of care on an occupier of premises to prevent (‘so far as reasonably practical’) risk to others of injury, which includes any disease and impairment.


n Workplace (Health, Safety and Welfare) Regulations 1992. Generally, you need to do everything reasonably practicable to protect people using your workplace from harm and make adaptations where necessary. Regulation 5, ‘Maintenance of workplace, and of equipment, devices, and systems’, states that ‘equipment that could fail and put workers at serious risk should be properly maintained and checked at regular intervals, as appropriate, by inspection, testing, adjustment, lubrication, repair and cleaning’. Regulation 6, Ventilation 52, meanwhile states: ‘Mechanical ventilation systems (including air-conditioning systems) should be regularly and adequately cleaned. They should also be properly tested and maintained to ensure that they are kept clean and free from anything which may contaminate the air’.


Inspecting and cleaning ductwork – air


To inspect or clean the inside of a duct, there must be a point of access via an inspection hatch. These must be readily accessible and sufficient in number to allow full system cleaning. The design and fitting of the ductwork by the architect and installer are therefore key to the cleaning and maintainability of a duct system. Filters should be changed on a regular basis to maintain the standard of cleanliness in the system. Fire dampers must be inspected annually in accordance with BS999:2017 Annexe W. Some older systems may still have fire dampers installed, and must be inspected, and tested to compliance with BS9999


Better design leads to better safety NAADUK’s membership has reviewed several examples of poor system design. These include: n a duct located behind a solid ceiling with no point of access.


n ducting located in a surrounded riser with no point of access, for example, a riser surrounded by wall fabric or brickwork.


n low-level plant, conduit, lighting, or other fittings obscuring the duct.


n an external riser. n a pitched roof exhaust. n a horizontally obscured duct with other services running alongside, above, or below.


n false, tiled, or suspended ceilings, restricting access to void and duct.


A dirty fire damper link.


Annexe W. If, during the inspection and testing procedure, the damper is damaged and cannot be repaired, then it must be replaced. Inspectors must be competent and aware that damper manufacturers change specification. Installers should always adhere to good practice; inspectors should always ask if the system is ‘Fan OFF’ or ‘FAN ON’.


Inspecting and cleaning kitchen ductwork


Filter systems can protect the fan, and should be routinely monitored, cleaned, and, when necessary, replaced. Carbon filters can be used to remove odours and smells associated with cooking, while wool-type pre-filters may also help reduce contamination at the point of entry into the duct system. All such measures alleviate the risk of fire in the system, and would curb its spread.


Fire can spread through the dust around the damper.


28 Health Estate Journal March 2021


Collaborative research As an association, we are constantly reviewing the impact of corrosive chemicals used on fireproof ductwork, and excessive panels cut into it that may affect its structural ability to resist collapse during a fire. NAADUK has tested several different samples of ductwork supplied by manufacturers, and made unidentifiable, so that no bias could affect the outcome. The aim was to see how the samples would respond to caustic chemicals used in commercial cleaning, combined with agitation from a rotary brush system. The findings were presented to the manufacturers via the Association for Specialist Fire Protection. In a few cases the intumescent seals were found to be damaged when using high concentrations of sodium hydroxide, a caustic cleaning chemical. It was concluded that a detergent-based cleaner, the use of grease scraping tools, or a combination of the two, would be a safer option to maintain ductwork integrity.


n no fan access. n two or more in-line components adjacent to each other in a duct system.


n silencer, fire-rated duct, insulation, or suppression systems, all of which might prevent ready access to ductwork to carry out maintenance.


n obscured access panels. n flat roof access without edge protection. n welded or riveted exhaust grilles preventing easy removal.


n a duct located directly over hoods or canopies, which will not support the weight of operatives and enable safe access for cleaning.


n open ceiling height. n data trunking or cabling physically restricting access.


n physical obstructions below the duct.


Recommendations and conclusions To conclude, there are several principles to consider when designing kitchen extraction ductwork. Firstly, avoid costly retrofit of panels or post-installation building works to provide access; access should be considered and installed at the time of fabrication or manufacture, as recommended in BESA DW 144, the Specification for Sheet Metal Ductwork. Secondly, eliminate the number of inaccessible sections. Keep the ductwork as short as possible, and make a feature of


A fire damper that will be unable to drop fully.


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