Some kitchen extract “cleans” never go further than the canopy. The hood is degreased, the filters are washed and the stainless steel looks spotless. But the grease that matters most for fire risk is often out of sight, in the plenum, the ductwork, the risers and the fan. This guide explains the difference between a canopy-only clean and a full system clean, and why the certificate should say exactly which one you’ve had.
Where grease actually builds up
Cooking vapour rises into the canopy, passes through the grease filters and travels along the duct towards the fan. Filters catch some of the grease, but not all of it. As the vapour cools in the duct, more grease settles on the inside walls. It collects on bends, in horizontal runs, in risers and around the fan blades and housing.
So the canopy is only the start of the system. The plenum behind the filters, the ductwork, the fan and the discharge all hold grease, and that grease is fuel.
Why a canopy-only clean leaves the risk in place
A flare-up on the range can be drawn up through the canopy into the duct. If the duct is lined with grease, a fire can take hold there and spread along the ductwork, sometimes through other parts of the building. Cleaning the canopy alone does nothing to remove that fuel.
It can also give a false sense of security. Staff see a clean hood and assume the job is done. Meanwhile, grease deep in the system keeps building up, clean after clean. Our guide to kitchen extract fires explains how these fires start and spread.
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.
What a full TR19 clean includes
A TR19® Grease clean covers the whole extract system:
- the canopy, inside and out, and the grease filters
- the plenum behind the filters
- all horizontal duct runs and vertical risers
- the extract fan and its housing
- attenuators, where fitted
- the discharge point
Ductwork is reached through access panels. Grease is scraped off by hand and removed with degreasers, hot water or steam, depending on the deposit. Grease readings are taken before and after, so you can see the difference. BESA’s guidance is that grease shouldn’t exceed a mean of 200 microns between cleans, and that 500 microns or more anywhere needs immediate spot cleaning (BESA).
The certificate must say what was cleaned
A certificate that just says “kitchen extract cleaned” isn’t enough. A proper post-clean certificate and report should list:
- each part of the system that was cleaned
- any sections that couldn’t be reached, and why
- grease readings before and after
- photos of the system before and after
- the recommended date for the next clean
If the report doesn’t mention the ductwork or fan, assume they weren’t cleaned. Insurers can look closely at this after a fire. See TR19 certificates explained for more red flags.
When canopy cleaning on its own makes sense
Canopy and filter cleaning still has a place. In busy kitchens, cleaning the canopy and changing filters between full system cleans keeps grease down at the point it enters the system. It just isn’t a replacement for the full clean. We offer canopy cleaning and a grease filter exchange service to sit alongside a full kitchen extract clean.
At Duct Doctor every full clean comes with a TR19® certificate and a photo report that shows what was cleaned, and records anything that couldn’t be reached.
Quick answers
Is a canopy clean the same as a TR19 clean?
No. A TR19 Grease clean covers the whole system, from canopy to discharge.
How can I tell what was cleaned last time?
Check the certificate and report. They should list each part of the system and include photos.
What if part of my duct can’t be reached?
It should be recorded on the report. Extra access panels can often be fitted so it can be cleaned next time.
Do I still need to clean filters?
Yes. Clean filters reduce the grease reaching the duct between full cleans.
Related services
More advice
- TR19 Certificates: What They Should Show
- Kitchen Extract Fires: How They Start and Spread
- Duct Access Panels: Why They Matter for TR19
- TR19 Explained: Kitchen Extract Cleaning Standard
- 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.