“How often should our extract be cleaned?” is the question we’re asked more than any other. The short answer comes from BESA’s TR19® Grease specification: somewhere between every three months and once a year, depending on how many hours a day you cook.
The longer answer is that the table is a starting point. What you cook, how you cook it, how well the filters are looked after and what the grease readings show all change the right interval. This guide explains the BESA minimums, the things that push a kitchen into a shorter cycle and how to set a schedule you can defend if an insurer or fire officer asks.
The BESA minimum intervals
BESA’s guidance on kitchen extract cleaning links cleaning frequency to daily use:
| Kitchen use | Typical daily cooking | Minimum cleaning interval |
|---|---|---|
| Heavy | 12–16 hours a day | Every 3 months |
| Moderate | 6–12 hours a day | Every 6 months |
| Light | 2–6 hours a day | Every 12 months |
“Daily use” means the hours the kitchen is actually cooking, not the hours the doors are open. A café that serves breakfast and lunch may be light or moderate. A hotel kitchen that runs breakfast, lunch, dinner and room service is likely to be heavy.
Why the table is only a minimum
BESA is clear that these intervals are minimums. The real interval should come from a risk assessment by a competent person, based on measured grease in the system. Two kitchens cooking for the same hours can produce very different amounts of grease.
If readings show grease building up faster than the schedule allows for, the clean should be brought forward. If a reading reaches 500 microns or more at any point, BESA’s guidance calls for immediate spot cleaning, whatever the calendar says.
How your cooking changes the answer
The type of cooking matters as much as the hours. As a rule of thumb, more fat and higher temperatures mean more grease carried into the extract. Kitchens that tend to need a shorter cycle include those that:
- deep fry for much of the day;
- use chargrills, griddles, rotisseries or woks at high heat;
- cook a lot of fatty meat;
- run solid fuel ovens or grills, which add soot and ash to the grease.
Kitchens that mainly steam, boil, bake or reheat usually produce less airborne grease. Even then, the extract still needs cleaning at least as often as the BESA minimum for its hours of use.
Grease readings set the real interval
Grease is measured in microns using a Wet Film Thickness Test (WFTT) or a Deposit Thickness Test (DTT). BESA’s figure to work to is that grease should not exceed a mean of 200 microns between cleans.
If readings taken at your clean show heavy deposits, the interval is too long. If readings taken partway through the cycle show very little, the interval may be about right. Over two or three cleans, the readings give you a clear picture of how fast your system collects grease. That’s the evidence behind a sensible schedule. Our guide on grease thickness testing explains how readings are taken.
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.
The parts that need attention between cleans
A professional clean every few months doesn’t replace daily and weekly care in the kitchen. The grease filters are the first line of defence. If they’re clogged, more grease gets past them into the plenum and duct, and airflow drops.
- Wash or swap filters as often as your use demands; many busy kitchens do this daily or several times a week.
- Wipe down the canopy surfaces and check the grease channels and drip trays.
- Don’t run cooking equipment without the filters in place.
If washing filters on site is a struggle, a grease filter exchange service swaps dirty filters for clean ones on a schedule. See also our grease filter cleaning guide.
Signs you’ve left it too long
Some warning signs mean the extract needs attention before the next booked clean:
- grease dripping from the canopy or filters;
- visible grease build-up around the filter housing or inside the canopy;
- the kitchen feeling hotter or smokier than usual;
- cooking smells lingering or spreading to other rooms;
- a noisy or vibrating extract fan;
- grease staining around the discharge outside.
Any of these is worth a call. Our list of signs your extract needs cleaning has more.
Other things that affect frequency
A few more factors can change the interval:
- Long or complicated duct runs. Grease settles at bends, in horizontal sections and near the fan.
- Shared risers. Where several kitchens use one riser, grease from all of them collects there.
- Seasonal trade. A pub that’s busy all summer may need a different pattern from one that’s steady all year.
- Your insurer’s wording. Some policies set their own interval. Check yours and follow whichever is stricter.
New kitchens and changes of use
A new kitchen, a new menu or a new operator changes the picture. A pub that switches from sandwiches to a full grill menu, or a café that adds evening service, may move up a band overnight. So may a kitchen that takes on delivery orders on top of its usual trade.
When anything like that happens, don’t wait for the old schedule to come round. Have the system surveyed and readings taken a few months after the change, then set a new interval based on what you find.
Setting a schedule you can stick to
The simplest approach is a fixed plan: 3, 6 or 12-monthly cleaning based on your hours and cooking style, adjusted once the first readings are in. A maintenance contract books each clean in advance, so it doesn’t slip when the kitchen gets busy.
Duct Doctor surveys the system first, takes readings, and recommends the next clean date on every certificate. We work evenings, overnight and at weekends so you don’t lose a service. If you’re not sure which band you fall into, call or email us and we’ll help you work it out.
Quick answers
How often should a restaurant kitchen extract be cleaned?
It depends on hours and cooking style. BESA’s minimums are every 3 months for 12–16 hours a day, every 6 months for 6–12 hours and every 12 months for 2–6 hours.
Is once a year enough?
Only for light use of around 2–6 hours a day, and only if grease readings support it. Busier kitchens need cleaning more often.
Who decides the right interval?
A competent person, using a risk assessment and grease thickness readings taken in the system. The BESA table is the minimum.
What if grease builds up before the next clean?
If any reading reaches 500 microns or more, BESA’s guidance calls for immediate spot cleaning of that section.
Can we clean the filters ourselves?
Yes, and you should, as often as your use demands. Filter cleaning doesn’t replace a full system clean of the plenum, ductwork and fan.
Related services
- Kitchen extract cleaning
- Grease filter exchange
- TR19 inspections and grease testing
- Canopy and hood cleaning
More advice
- TR19 Explained: Kitchen Extract Cleaning Standard
- Grease Thickness Testing: WFTT and DTT Explained
- Signs Your Kitchen Extract Needs Cleaning
- Grease Filter Cleaning: How Often and How
- Restaurant Kitchen Extract Cleaning: A Guide
- 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.