Roof fan cleaning the end of the duct most people ignore

Because all the grease-laden air passes through it, so it collects grease heavily - and a grease-laden roof fan is a fire risk, works harder for less, and means the system isn't actually clean; a proper clean includes it. The roof-mounted extract fan draws all the extracted air through the system, so all the grease-laden air passes through it and grease collects heavily on the fan blades, housing and surrounds. That build-up is a problem: it's a fire risk (a heavy grease accumulation up on the roof that can ignite, dangerous and hard to reach); it makes the fan work harder and less efficiently (grease loads and unbalances it, so it moves less air for more energy and wears faster, risking a breakdown); and it means the system isn't genuinely clean or compliant (a proper clean is roof-to-canopy). So the roof fan - one of the greasiest, highest-risk parts - needs cleaning as part of the whole-system clean. So because it's greasy, a fire risk, and part of a real clean. So to control grease, fire risk and wear. This is general guidance.

Because it's out of sight (up on the roof, not in the visible kitchen) and hard to reach (needing roof access and working at height), so it's tempting to clean the visible kitchen end and skip the fan - but that leaves the greasiest part uncleaned. The roof fan is the most-neglected part of the extraction for a simple reason: it's out of sight and awkward to reach. Out of sight - it's on the roof, not in the kitchen where grease is visible and prompts attention, so nobody looks at it day to day. Hard to reach - getting to it means roof access and working at height, which is awkward and sometimes hazardous, needing the right equipment and precautions. So a less thorough or cheaper clean may do the visible, accessible kitchen end (canopy, filters, reachable duct) and quietly leave the roof fan out, with the customer none the wiser (it's not somewhere they'll look). But it's ignored because of where it is, not because it doesn't matter - in fact it's one of the greasiest, highest-risk parts. So because it's out of sight and hard to reach. So its awkward location gets it skipped. This is general guidance.

Yes - a heavy grease accumulation on and around the roof fan is fuel, and a fire there is dangerous and hard to reach, up high near the roof structure; the fan is also where heat and any duct fire would pass, so it's a serious fire hazard. A grease-laden roof fan is a genuine fire risk. All the grease-laden air passes through it, so grease builds up heavily on the fan, in the housing, and in the roof void or on the roof around it - a substantial accumulation of combustible grease. If it ignites (grease fires can start from the heat of cooking carried through, or spread from a duct fire), the fire is in a dangerous spot: up high, near the roof structure, hard for anyone to reach and tackle, and potentially spreading to the building's roof. The fan is also the point through which heat and any flame in the ductwork would pass. So a greasy roof fan combines a lot of fuel with a bad location (as covered in what happens in the roof void when grease ignites). So yes - it's a serious fire risk, which is a key reason to keep it cleaned. So yes; a greasy roof fan is a real hazard. This is general guidance.

Yes - grease loads and unbalances the fan, so a greasy one moves less air for more energy and wears faster; cleaning it restores the airflow, lowers the running cost, and reduces the risk of a breakdown. The roof fan drives the whole extraction, so its condition affects how the system works. When grease builds up on the fan, it loads and unbalances it: the fan moves less air (weaker extraction at the canopy) while drawing more energy (higher running cost), and it wears faster (the imbalance and load strain the bearings and motor), heading toward a breakdown of the very fan the system depends on. Cleaning the grease off restores the fan's balance and performance: it moves air freely again (better extraction), runs more efficiently (lower energy use), and is under less strain (longer life, fewer breakdowns) - as covered in the overworked-roof-fan and seized-fan pages. So cleaning the roof fan isn't just about fire safety - it improves the extraction, cuts running cost, and improves reliability. So yes - it restores airflow, efficiency and reliability. So yes; a clean fan works better and lasts longer. This is general guidance.

No - a proper clean is roof-to-canopy (the whole system), so stopping short of the roof fan leaves the greasiest part uncleaned and the certificate incomplete or misleading; make sure the fan is explicitly included. A proper extraction clean covers the whole system - roof-to-canopy - including the roof fan. A clean that stops short of the fan is not a complete clean: it leaves the greasiest, highest-risk part uncleaned, so the system isn't genuinely clean or its fire risk properly controlled. And the certificate becomes questionable - it can't honestly certify a system to the TR19 Grease standard when the fan (a key part) wasn't cleaned, so a certificate issued anyway is incomplete or misleading. So a clean that skips the roof fan isn't really valid or compliant, even if a certificate is produced. This is why you should make sure the roof fan is explicitly in the scope of the clean (ask, don't assume) and check the certificate and photographs cover it. So no - a clean that skips the fan isn't complete or properly compliant. So no; the fan must be included. This is general guidance.

By a contractor set up for roof work - with safe roof access, working-at-height equipment and precautions, and a competent crew - who cleans the fan, housing and surrounds of grease and checks its condition, as part of the whole-system clean. Cleaning the roof fan is roof work at height, so it must be done safely. That means proper provision: a safe way onto and around the roof, the right working-at-height equipment and precautions, and a competent, equipped crew who can work safely up there (as covered in working at height on roof fans). With that in place, the cleaners remove the grease from the fan blades, the housing and the surrounding area (the accumulation that's the fire risk and the drag on performance), and check the fan's condition and running while they're there (spotting any developing problem). This is done as part of cleaning the whole system to the TR19 Grease standard, verified and recorded, with the fan included in the certificate and photographs. So it needs a contractor equipped and willing to do the roof work safely - which is part of why choosing the right cleaner matters. So safely, by an equipped crew, as part of the full clean. So by a competent crew set up for working at height. This is general guidance.