What type of Grease Filter?

There is a lot of misinformation in the Catering / Restaurant trade regarding whether or not it is “legal” to use mesh type grease filters in a kitchen canopy. So let’s address this point first.

According to HVCA Specification for Kitchen Ventilation Systems DW172, if you have an existing canopy which was designed to use mesh grease filters then there is no obligation to change your filters to the baffle type, when your old mesh filters need replacing. Your extraction system was designed to use mesh filters, so switching to baffle filters without making any other alterations to the system could have a negative impact on the system’s performance

However, any new extraction system should not be designed with a mesh filter (or any other type of filter that holds the captured grease within the filter) as the primary filter in the canopy. Whilst this is not a legal requirement, failure to follow this specification could impact on any insurance claim made in the event of a kitchen fire. Any new system manufactured since 2005, should use a baffle type filter as the primary canopy filter

Why is this?

The reasons for this are fairly self evident. Mesh filters hold the captured grease within the filter. Without regular, thorough cleaning, this grease represents a fire hazard, as any flash fire on the cooking surface below, could ignite the grease in the filter – which in turn could travel into the duct, allowing it to spread throughout the building , with disastrous, if not fatal consequences

Baffle filters remove this risk, as they work in an entirely different way. The filter comprises a row of opposing V or U shaped blades or vanes. As the air travels through the filter, it is forced to change direction several times. As it does so, the grease separates from the air and is deposited on these “vanes”. The liquid grease runs down the vanes, out through drain holes in the bottom of the filter, and into a drip tray or other draining mechanism for removal. Because no grease is held within the filter itself, the fire risk is removed. Baffle filters also act as a flame barrier, preventing fire from reaching into the ducts and spreading

So why not just switch from Mesh to Baffle?

Firstly, because mesh filters capture the grease, holding it until it is removed by cleaning, the canopy may not have a draining facility for liquid grease –either a drip tray or run off gulley & drain point. If baffle filters are simply installed in place of mesh filters, then the grease that is drained from the filter has nowhere to go. It will accumulate in the bottom of the canopy, until it either overflows, or begins to seep through any joints. It may also be sucked up into the ductwork system by the air travelling through the canopy, coating the inside of the ductwork

Secondly, baffle filters require a slot velocity of around 4.5 -5.5 m/s which, if not achieved, will result in the grease being carried through the filter where is will deposit on the duct surfaces, increasing cleaning costs. Pressure losses across baffle filters are also much higher than across mesh filters. This increase in resistance can result in a reduction in airflow, creating a poorly ventilated, smoke -filled kitchen and in extreme cases, complete fan failure. It is therefore imperative that the right fan is selected when using baffle filters

So whilst it is possible to switch from Mesh to Baffle Filters, this is only possible if the correct modifications to both canopy and fan have been implemented


For further questions please contact the sales team on 01474 325666 or sales@acefiltration.co.uk

24th June 2013 Posted by admin

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