The kitchen extract system presents particular hazards due to the potential for the accumulation of grease. Accumulated grease within an extract system forms a hidden combustion load. Under certain circumstances flame or very high temperature within the duct can ignite the grease causing fire to spread rapidly through the duct. Flame and heat within the duct can ignite surrounding materials at various points along the ductwork path and transfer fire in ways that are difficult to predict and control by designers, installers and ultimately fire fighters.
The Health & Safety Executive and industry and insurance guidance and regulations stipulate that kitchen extract systems should be kept clean to minimise fire and other risks. Your insurers and the environmental health officer will expect you to risk assess and undertake routine and regular inspections and cleaning.
The HVCA document TR19 ‘Cleanliness of Ventilation Systems’ provides specific guidance on methods of measuring and defining cleanliness as a bench mark for good practice. The frequency of cleaning should be adjusted by means of system testing (inspection and monitoring) so that surface grease deposit limits are not exceeded. The buildings insurance company should be consulted to ensure that the cleaning regime is compliant with the terms of their specific warranty. Any cleaning regime should be justified by a considered risk assessment. (The latest Fire Precautions Workplace and Management of Health & Safety at Work Regulations apply). Regular cleaning will result in an improved mean standard and reduce the costs of cleaning as deposits are not allowed to bake and harden.
Frequency of Cleaning – TR/19 HVCA
Guide to Good Practice Internal Cleanliness of Ventilation Systems
The need for specialist cleaning of extract systems will depend on the level of usage of the cooking equipment, types and quantity of cooking and other risk factors such as vulnerability of the system to ignition and of the building and its occupant/users to system fire, hygiene, vermin and mechanical hazards
TR19 Table 11: Frequency of Cleaning