Guide
Kitchen Extraction Fan Not Working: What To Do
My kitchen extraction has stopped. What do I do first?
Stop the gas appliances, then check the isolator, the breaker and the grease filters, in that order. Those three account for most extraction that stops without warning and all three are safe to check from the kitchen floor. If the fan still will not run, or it runs and pulls nothing, the kitchen should not carry on cooking on gas.
Can we keep cooking?
On a gas line, no. Where a commercial kitchen has gas catering appliances and mechanical ventilation, the gas is only meant to be available while that ventilation is proven to be running, and a working interlock will have closed the valve for you already. If the interlock has not closed and the extraction has genuinely stopped, that is a second fault sitting underneath the first. How the interlock decides.
On an electric line the answer is a judgement rather than a rule, and the thing to judge is whether the kitchen is still clearing. Food hygiene law requires suitable and sufficient ventilation in a food preparation area, and mechanical airflow from a contaminated area to a clean area is to be avoided. A kitchen holding smoke fails both tests, and it will be recorded that way if an environmental health officer walks in during it.
Whatever the outcome, write down the time it stopped and what the kitchen did next. If this becomes an insurance or an enforcement conversation later, that note is the difference between a decision you made and a decision you cannot account for.
What can I check before calling anyone?
Five things, and none of them needs a tool or an enclosure opened. Work down the list in order. Each one rules out the one below it.
| Check | How | What the answer tells you |
|---|---|---|
| Is the isolator on? | The rotary isolator is usually on the wall near the canopy or beside the fan. A cleaner, a delivery or a contractor working on something else can knock it off. | If this was it, the fan restarts and nothing else needs doing. |
| Has a breaker tripped? | Look at the distribution board for a breaker sitting out of line with its neighbours. Reset it once. | If it trips again, stop. A breaker that trips twice is reporting a fault, not a nuisance. |
| Are the grease filters loaded? | Lift one out and look at it against the light. Filters come out by hand and go in a sink. | Loaded filters throttle a healthy fan and are the most common cause of extraction that faded rather than stopped. |
| Can you hear the fan at all? | Stand under the canopy with the extract switched on and listen, then hold a sheet of paper flat under a filter. | Silence points at power or the motor. Noise with no pull points at the belt, the filters or the duct. |
| Is anything else on the same panel dead? | Check the canopy lights and any second fan on the same control panel. | One dead item is a local fault. Several is the supply or the panel. |
Nothing on that list involves opening a control panel, a fan housing or an isolator. Resetting a motor overload inside a panel appears on a surprising number of troubleshooting pages written for kitchen managers. Under the Electricity at Work Regulations 1989 that is work on an electrical system, and it needs somebody competent with the system dead and proven dead.
Why is the fan not working but the light is on?
Because they are usually two circuits. Canopy lighting is commonly fed and switched separately from the extract fan, so a lit canopy tells you the panel has power and tells you nothing about the fan. It is a useful symptom rather than a confusing one: it rules out the incoming supply and points at the fan circuit, the contactor, the motor overload or the motor itself.
Where a system has an interlock or a pressure switch, the same picture appears when the control side has decided not to let the fan run. The lights are unaffected because the control never touched them.
Why will the extractor fan not switch off?
Three usual causes, in the order they turn up. A run-on timer doing its job, and the fan will stop by itself once it expires. A control panel left in hand rather than auto, which happens after somebody works on the system and does not put the switch back. Or a contactor whose contacts have welded closed, which is a real fault and the reason a kitchen should report this symptom rather than live with it.
The last one matters more than it sounds. A welded contactor means the fan cannot be stopped by its own controls, so it also cannot be stopped by an interlock or by a fire alarm interface that expects to stop it.
The fan is running but the extraction is weak
This is a different fault from a fan that has stopped, and it is the more common of the two. The fan sounds healthy because it is healthy. What has changed is what it is being asked to move air through.
- Loaded grease filters. The first thing to rule out and the easiest to fix.
- A duct run narrowed by grease. Gradual, so the kitchen adapts to it and nobody notices until it is halfway there.
- A slipping belt. The fan turns, just not at the speed it was commissioned at. Common on belt driven fans and invisible from the floor.
- Not enough make-up air. A fan cannot move its rated volume out of a room that has no way of replacing it. This one is mistaken for a failing fan more often than any other.
The last one is why an engineer measures before replacing anything. Extraction that seems weak is often an air supply problem, and a new fan fitted to a kitchen that cannot breathe performs exactly like the old one. Why make-up air decides this.
Why does the extraction smell of burning?
Stop and isolate the system. A burning smell from a canopy, a fan or a duct run is one of the few symptoms in this trade that is worth acting on before it is diagnosed, because two of its causes involve heat arriving somewhere grease already is.
A slipping belt glazing against its pulley smells of hot rubber. A dry bearing or a motor winding under strain smells sharper and hotter. Grease deposits close to a hot appliance or a failing light fitting smell of cooking that nobody is doing. None of the three fixes itself, and the third is how extract system fires start.
When does it stop being a check and start being a repair?
When any of the following is true, the useful next step is an engineer rather than another check:
- A burning smell from the canopy, the fan or the duct
- Smoke that is not clearing from the cooking line
- A gas interlock that has closed the gas valve
- A breaker that trips again as soon as it is reset
- Visible grease running from a joint, an access panel or a light fitting
- Vibration heavy enough to be felt through the canopy or the wall
What an engineer does that a check cannot is measure. Airflow against the commissioned figure, current against the motor’s rating, belt condition, filter loading and the state of the duct behind the access panels. That turns a symptom into a named fault, which is what the kitchen actually needs before anyone quotes for parts. How we diagnose extraction faults, and emergency extractor fan repair when it cannot wait.
Sources
- Regulation (EC) 852/2004 on the hygiene of foodstuffs, Annex II Chapter I, ventilation. Checked 16 August 2026: source
- Electricity at Work Regulations 1989. Checked 16 August 2026: source
- BS 6173:2020, installation and maintenance of gas fired catering appliances. Checked 15 August 2026: source
- Regulatory Reform (Fire Safety) Order 2005. Checked 15 August 2026: source