Filters that won't come clean: time to act

When it won't come clean however you wash it - it stays clogged with baked-on grease, the mesh is matted or damaged, or the frame is bent or corroded. A grease filter is meant to be washed and reused, so after a proper clean it should come back reasonably clean and sound. It needs replacing when cleaning no longer restores it: (1) the grease is baked on so hard that washing (even soaking and scrubbing) won't clear it, so it stays greasy and clogged; (2) a mesh filter's mesh is matted solid, crushed or torn, so it no longer filters or cleans; or (3) the frame is bent, damaged, split or corroded (rusted), so it no longer fits or functions. A simple check is to look at the filters after cleaning - any that stay clogged or are visibly damaged are spent and need replacing. So you know a filter needs replacing when it won't come clean or is physically damaged after a proper wash. So it needs replacing when cleaning no longer restores it. This is general commentary.

Because a spent filter doesn't do its job - it lets grease past into the system, so keeping it in place leaves a hole in your first line of defence. The filter's purpose is to catch grease before it gets into the canopy, ductwork and fan. A filter that won't come clean fails at this: if it's clogged solid, it can't catch more grease and it chokes the airflow; if the mesh is matted, holed or damaged, or the frame no longer seals, grease passes straight through or around it. Either way, the grease it should catch instead gets past it, loading the whole system (more grease in the ductwork and on the fan - more fire risk, and cleaning needed sooner). So keeping a spent filter isn't saving anything - it's leaving the system less protected and loading it faster. Replacing it (a small cost) restores the defence. So don't keep using a spent filter - it lets grease reach the system. So keeping a spent filter leaves the system unprotected. This is general commentary.

Usually grease baked on hard (often from being left too long between cleans), or the filter being worn or damaged over time. The main cause is grease that has built up and baked on: if a filter is left too long without cleaning, the grease accumulates and, with the heat, bakes on hard - reaching a point where even soaking and scrubbing won't remove it. So letting filters go too long between cleans can hasten their end (a reason to clean them regularly). The other causes are wear and damage over time: a mesh filter's mesh matting, crushing or tearing; a frame bending, splitting or corroding (rusting) through use, heat and washing. So a filter becomes impossible to clean either from baked-on grease (often neglect) or from wear and damage - both natural, though regular cleaning slows the grease cause. When it happens, the filter is spent and needs replacing. So baked-on grease or wear and damage make a filter impossible to clean. This is general commentary.

A like-for-like filter of the correct type and size for your canopy - the same type (baffle, mesh or cartridge) and the right dimensions to fit and seal properly. Grease filters come in types (baffle, mesh, cartridge) and sizes, and a canopy is designed for a particular type and size - so a replacement should match: the same type (unless you are deliberately changing type on advice), and the correct dimensions to fit the canopy's filter housing properly and seal (a filter that doesn't fit well leaves gaps for grease to bypass). Baffle filters are common and robust (as covered in baffle filters vs mesh filters); the right choice depends on your canopy and cooking. So get a like-for-like replacement of the correct type and size - or take advice if you are considering a different type. A competent extraction cleaner can advise on and supply the correct filters for your canopy. So get a correct-type, correct-size replacement filter. This is general commentary.

Yes - a competent extraction cleaner will typically flag filters that are past cleaning (won't come clean, or are damaged or corroded) during the professional clean, and can advise on replacements. As part of a professional extraction clean, the filters are cleaned - and in doing so, the cleaner sees their condition: which come clean and which don't, and any that are matted, damaged or corroded. So a good cleaner will flag the spent filters (those that won't clean or are damaged) and let you know they need replacing - and can usually advise on, or supply, the correct replacements. This is a useful check (an expert eye on the filters' condition), on top of your own in-house observation. So yes - an extraction cleaner will usually flag filters that need replacing and can help you replace them. It is worth asking them to note the filters' condition. So yes - a good cleaner flags spent filters and advises on replacements. This is general commentary.

There's no fixed schedule - filters are replaced when they reach the end of their life (when cleaning no longer restores them), which depends on use, cooking type and how well they're maintained. Unlike the cleaning interval (which is regular and scheduled), filter replacement is condition-based: you replace a filter when it's spent, not on a fixed timetable. How long a filter lasts varies - heavy, greasy cooking wears filters faster (more grease to bake on); regular, proper cleaning extends their life (preventing the baked-on build-up that kills them); and physical damage or corrosion can end a filter at any time. So some filters last a long time, others need replacing sooner. The practical approach is to check the filters' condition (especially after cleaning) and replace those that won't come clean or are damaged - rather than expecting a set replacement interval. So filters are replaced when they're spent, at a frequency that depends on use and care - checked by condition, not a fixed schedule. So replace them when spent, based on condition. This is general commentary.