We walked into a restaurant kitchen in Soho last summer. It was 46°C. The head chef was working in shorts and a soaked t-shirt. The extraction canopy above the charcoal grill was running flat out and achieving nothing. The make-up air system? Didn’t have one. They were trying to cool the kitchen by propping the back door open, which was pulling exhaust fumes from the alley straight through the food prep area.
This isn’t unusual. Overheating kitchens are one of the most common problems in London’s restaurant scene, and the root cause is almost always the same: the ventilation was either designed wrong, installed wrong, or never designed at all.
Our engineers see this fault regularly across Shoreditch. A PPM contract catches this kind of issue early, well before it escalates into a costly commercial AC installation.
What the Regulations Actually Say
Commercial kitchen ventilation isn’t optional — it’s a legal requirement. Building Regulations Part F covers ventilation in non-domestic buildings, and the industry standard that matters is DW/172 — the BESA specification for kitchen ventilation systems.
DW/172 sets out the design requirements: canopy types, extraction rates, make-up air volumes, grease filtration stages. If your kitchen ventilation wasn’t designed to this spec, there’s a good chance it’s not extracting enough air for the heat load your equipment is throwing out.
Gas safety adds another layer. If you’ve got gas cooking equipment, the ventilation system needs to supply enough air for combustion as well as heat removal. An extraction system that’s too powerful without adequate make-up air creates negative pressure in the kitchen — and that can interfere with gas appliance flues. Dangerous territory.
Why Your Kitchen Is Too Hot
Not Enough Extraction
Most common issue we see. The kitchen canopy is either too small for the cooking line, or the extraction rate (measured in litres per second or m³/hour) is too low for the heat output of the equipment underneath it.
This happens a lot when kitchens evolve. A restaurant opens with a small menu and modest equipment. Three years later they’ve added a charcoal grill, a tandoor oven, and two extra fryers. The cooking capacity has doubled but the extraction system is exactly the same. The canopy that was adequate for the original fit-out is now hopelessly undersized.
The only fix is matching the extraction to the heat load. That might mean a larger canopy, higher-capacity fans, or additional extraction points over the new equipment. We carry out heat load calculations to DW/172 and design the extraction around what’s actually in the kitchen, not what was there five years ago.
No Make-Up Air
This is the one most people don’t think about. Every cubic metre of air you extract from a kitchen has to be replaced by fresh air from somewhere. If there’s no dedicated make-up air system, that replacement air gets pulled in through doors, windows, gaps under walls — wherever it can find a way in.
The problems: uncontrolled draughts that mess with cooking equipment, doors that are hard to open because of negative pressure, and in winter, a blast of freezing air hitting the chef every time someone opens the kitchen door. Some kitchens get so negative that the extraction system itself can’t work efficiently because there’s not enough incoming air to push against.
A proper make-up air unit — tempered in winter so it’s not blowing 2°C air into a 35°C kitchen — transforms the working environment. Air goes in at a controlled rate, gets heated up by the kitchen equipment, and gets extracted by the canopy. The kitchen stops fighting against itself.
Grease Filters Blocked
The baffle filters in your extraction canopy trap grease before it enters the ductwork. When they’re clean, they let air pass through while capturing grease particles. When they’re caked in weeks of accumulated cooking fat, they restrict airflow like a pillow over the vent.
Grease filters should be cleaned weekly at minimum — more often in high-volume kitchens. They’re designed to be removable and dishwasher-safe. If your kitchen staff aren’t cleaning them regularly, extraction performance drops, the kitchen gets hotter, and grease starts migrating into the ductwork where it becomes a fire risk.
Spot Cooling Needed
Even with perfect extraction, some areas of a commercial kitchen will always be hot. The pass (where plated food sits under heat lamps), the area around the charcoal grill, and the dishwash section all generate intense localised heat. Extraction deals with the overall kitchen air, but these hotspots need targeted cooling.
We install spot cooling units — small, focused AC units designed for commercial kitchen environments. They’re not trying to air-condition the whole kitchen (which is a losing battle when the grill’s on); they’re putting a stream of cooled air exactly where the chef is standing. The difference for staff comfort and productivity is immediate.
If you are also experiencing kitchen extraction not pulling properly, the two faults may share a common cause. Our engineers frequently find that addressing one resolves the other. You might also want to read our guide on dishwasher areas running too hot and humid for additional troubleshooting steps.
Duct Cleaning and Fire Safety
While we’re on the topic: when was your kitchen ductwork last cleaned? Grease accumulation in extract ducts is one of the leading causes of kitchen fires. The insurance companies know this — many policies require annual duct cleaning with a certificate of compliance.
TR/19, the BESA guide to ductwork hygiene, sets out the cleaning standards. A proper duct clean includes access panels, visual inspection, internal cleaning, and photographic evidence of the before and after state. If your kitchen extraction hasn’t been cleaned internally since it was installed, it needs doing.
The Full Picture
A commercial kitchen ventilation system isn’t just a canopy and a fan. It’s extraction matched to heat load, make-up air to replace what’s extracted, grease filtration to protect the ductwork, and potentially spot cooling for the worst hotspots. All of it designed as one system, not cobbled together piece by piece.
We design, install, and maintain kitchen ventilation systems across London’s restaurants, hotels, pubs, and commercial catering operations. We understand DW/172 requirements and can assess whether your current setup is actually doing its job — or just making noise.
Call us on 020 3974 1419 to arrange a kitchen ventilation assessment. Or if it’s already 45°C in there and you need help now, we can do that too.