Commercial Kitchen Extract Systems
Commercial (or non-domestic) kitchen extract ductwork is frequently referred to within the mechanical industry as 'grease ducting'. Due to the constant accumulation of cooking oils, fat residues, and carbonised deposits, this type of infrastructure carries an incredibly high risk of spontaneous ignition and intense internal fires. These fires burn with greater intensity than standard ventilation networks, fuelled heavily by cooking fats.
Fire Testing Compliance Categories
To safely meet structural fire regulations, kitchen extract systems must be rigorously evaluated for both Type A (fire outside the duct) and Type B (fire inside the duct) scenarios. Testing for both cases is vital; it ensures that a fire originating in one room won't ignite grease inside a duct passing through, and conversely, an internal grease fire won't transfer radiant heat intense enough to spark a secondary outbreak in adjacent zones.
BS 9999 Regulatory Requirements
In strict compliance with BS 9999, your installation layout must adhere to the following passive system metrics:
- Non-domestic commercial kitchen hubs are required to use completely separate and independent extraction plant networks.
- Moving mechanical fire dampers should not be built into any Kitchen Extract ductwork runs, as closing them traps grease and fuels fires.
- Clean-out access doors must be physically installed at maximum 3-metre intervals across the layout wherever possible.
- All internal raw metal surfaces must be perfectly smooth to prevent fat deposits from building up and to aid standard maintenance cycles.
Compartmentalisation & Radiant Heat Protection
Where an extract run cannot exit directly to the outside atmosphere from the initial kitchen area, the ductwork must be fire-resisting from the exact boundary where it leaves that compartment all the way to its external discharge termination point. While general ventilation plant networks may shut down in an emergency, grease ducts must maintain absolute stability, integrity, and thermal insulation. Specifying insulated fire-resisting properties is key to blocking high radiant heat from igniting materials surrounding the structural build.
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