A kitchen extract that needs cleaning usually tells you. The trouble is that the signs creep up slowly, so staff get used to them. A little more heat here, a louder fan there, and before long the system is struggling. This guide lists the common warning signs, what each one means and when to call for a clean or an inspection.
Smoke and steam hanging in the kitchen
If smoke and steam linger over the range instead of being drawn up into the canopy, the system isn’t moving enough air. The cause is often clogged filters, a greasy duct narrowing the airway or a fan coated in grease. All of them mean less extraction and more heat and fumes for the chefs. A kitchen that feels hotter than it used to, with the same equipment and the same menu, is often showing the same problem.
Grease dripping from the canopy
Grease dripping from the canopy edge, light fittings or filter housings is a clear sign. It means grease is building up faster than it’s being removed. Drips onto cooking surfaces are a food hygiene problem too, and something an EHO is likely to notice. See EHOs and kitchen extraction.
Noise, vibration and a struggling fan
Grease building up on fan blades can unbalance them. That causes vibration, rattling and a louder hum than usual. Over time it puts extra strain on bearings and the motor. If the fan sounds different, it’s worth having it looked at. Our guide to extract fan problems explains how to tell grease imbalance from mechanical wear.
Need it done? Duct Doctor cleans and tests kitchen extract and ventilation systems across London and the South East, with a certificate and photo report after every clean. Get a fixed quote.
Smells and condensation
Stale cooking smells in the kitchen, in nearby rooms or outside near the discharge can come from old grease in the system. Condensation drips from ductwork or the canopy are another sign: grease and moisture together make a sticky residue that can leak through joints. Neighbours complaining about smells is a clue too. See odour control maintenance if you have filters or units fitted to deal with smells.
Visible grease and paperwork clues
Look inside the canopy with a torch. If you can see grease on the plenum behind the filters, there’s likely more further along the duct. Then check your records:
- Is the date on the last certificate past the recommended next clean?
- Has the kitchen got busier, opened longer or changed its menu since the last clean?
- Did the last report record sections that couldn’t be reached?
- Is there no certificate at all?
Any “yes” is a reason to book a clean or an inspection. BESA’s minimum intervals run from every 3 months for heavy use to every 12 months for light use, and grease readings over a mean of 200 microns mean the system is overdue (BESA).
What to do next
If you notice any of these signs, start with an inspection. A TR19 inspection with grease thickness readings shows how much grease is in the system and where. If readings anywhere are 500 microns or more, BESA guidance is that spot cleaning is needed straight away. Duct Doctor can survey from photos and details or on site, give you a fixed quote, and clean when the kitchen is closed. For urgent problems there’s a 24/7 emergency callout.
Quick answers
Can I see inside the duct myself?
Only near the canopy. The rest needs access panels, which is a job for the cleaning team.
Does a noisy fan always mean grease?
Not always. Worn bearings or motor faults can cause noise too. An inspection will tell you which.
What if we’ve never had a clean?
Book an inspection or survey first. It shows the condition of the system and what a first clean will involve.
Related services
- Kitchen extract cleaning
- TR19 inspections and grease testing
- Extract fan cleaning
- Grease filter exchange
More advice
- How Often Should a Kitchen Extract Be Cleaned?
- Kitchen Extract Fan Problems and What They Mean
- Grease Thickness Testing: WFTT and DTT Explained
- Grease Filter Cleaning: How Often and How
- All advice
This guide is general information. It isn’t legal or insurance advice: check your own policy wording and lease, and speak to a qualified adviser about your fire risk assessment.