Ventilation · 2026
Commercial Kitchen Make-up Air and Getting Your Kitchen Air Balance Right
If your commercial kitchen feels cold, draughty, or fills with fumes and steam that the extraction system never quite clears, the fault is often not the extract canopy itself. It is a lack of commercial kitchen make up air to replace what the fans are pulling out. Getting the balance right keeps the room comfortable, keeps extraction working as designed, and keeps the kitchen on the right side of ventilation guidance.
The Basics
What Commercial Kitchen Make-up Air Actually Does
Every kitchen extract fan removes a set volume of air, along with heat, grease and steam, from the room. That air has to be replaced from somewhere. Commercial kitchen make up air is the supply system designed to put clean, tempered air back into the space at roughly the same rate it is being extracted.
Why the balance matters
When there is no deliberate supply, the extraction system pulls air from wherever it can find it: gaps under fire doors, corridors, the dining room, or in the worst cases the flue of a gas appliance. That last scenario can pull combustion products back into the room instead of up the flue, which is a genuine safety issue rather than just a comfort problem. The HSE ventilation guidance is clear that supply and extract need to work as a pair, not as two separate systems installed at different times by different contractors.
The practical result of poor balance is a kitchen that feels either freezing at floor level or thick with steam and fumes, sometimes both at once depending on where you are standing. Extraction fans running flat out are doing very little useful work if the room cannot draw in enough replacement air to let them function.
Warning Signs
Signs Your Kitchen Extract and Make-up Air Are Out of Balance
Most kitchens with a balance problem show more than one of these symptoms at once. On their own each might look like a minor annoyance, but together they usually point to the same root cause.
Doors that slam or won't open
Fire doors and back doors held shut, or slamming on their own, are a classic sign of negative pressure caused by extraction with nothing replacing the air it removes.
Cold draughts at floor level
Untempered air being dragged in through door gaps and service openings feels like a draught because it hasn't been warmed or filtered before it enters the room.
Fumes and steam that linger
If the canopy is running but the air still looks hazy or smells strongly ten minutes after service, the extract fan cannot pull enough replacement air to do its job properly.
Cooking smells reaching the dining room
A kitchen under strong negative pressure will draw air, and odours, from the front of house rather than keeping them contained behind the pass.
Getting the Numbers Right
Calculating Commercial Kitchen Make-up Air Correctly
Balancing supply and extract is not a case of matching the figures exactly. A kitchen usually works best with a small deliberate shortfall in supply, so odours are drawn into the extraction rather than pushed out into the dining room.
Set supply at roughly 80–90% of extract
This keeps the kitchen very slightly negative to its surroundings, containing fumes and steam, without starving the extract fans of the air they need to work.
Temper the incoming air
Cold air blown straight in without heating simply moves the draught problem rather than solving it. A tempered or heated make-up air unit keeps staff comfortable in winter.
Position diffusers away from the canopy
Supply air blowing directly across the canopy face disrupts capture and pushes grease-laden air back into the room instead of up the duct.
Test, balance and record the result
A commissioning engineer should measure both airflows on site and issue a balancing certificate, following BESA-aligned practice, so you have proof the system meets the design figures.
What's Involved
What a Make-up Air Fix Includes
Correcting a kitchen air balance problem is rarely a single component swap. It usually means looking at supply and extract together as one system.
Airflow survey
Measuring existing extract and supply volumes on site to establish exactly how far out of balance the kitchen currently is.
Make-up air unit sizing
Selecting a heated or tempered supply unit sized correctly against the extract rate, rather than an off-the-shelf fan that happens to fit the space available.
Ductwork and diffuser layout
Routing supply air to enter the kitchen without disturbing canopy capture, avoiding cold spots and hot spots across the cooking line.
Commissioning and certification
On-site testing to confirm the finished system matches the design figures, with a certificate kept for insurance and environmental health purposes.
If you are planning a wider refit alongside the air balance work, our kitchen extraction and ventilation service covers design, supply and installation as one project rather than a series of separate jobs. Call 01304 249963 to talk through what your kitchen needs, or book a site visit so we can measure the airflows in person.
The most reliable way to find out what is actually happening in your kitchen is to have someone measure it. Book a site survey and we will check extract and supply volumes, look at diffuser placement, and tell you plainly whether the problem is the extract, the supply, or both.
Questions We're Often Asked
Make-up Air FAQs
What is make-up air in a commercial kitchen?
Make-up air is the supply of clean, tempered fresh air brought into a kitchen to replace the air removed by extraction fans and canopies. Without it, extraction has to pull replacement air in from wherever it can, often through gaps around doors and appliances, which causes draughts and pressure problems.
How much make-up air do I need compared to extract?
A common starting point is supply air set at around 80 to 90 percent of the extract rate. This keeps the kitchen slightly negative to surrounding areas, which helps contain fumes and steam, while still giving the extraction fans enough air to work properly. The exact figure depends on kitchen layout and appliance load, so it should be measured on site rather than assumed.
Can too much make-up air cause problems?
Yes. If supply air matches or exceeds extract, the kitchen can become positively pressurised, pushing cooking smells and steam out into the dining room or corridors instead of containing them. Balance matters as much as raw volume.
Do I need a heated make-up air unit?
In most UK kitchens, yes. Supplying cold, untreated fresh air directly into a working kitchen usually just relocates the draught problem rather than solving it. A heated or tempered supply unit keeps staff comfortable, particularly through winter months.
Is make-up air a legal requirement?
Workplace ventilation, including in commercial kitchens, is covered by general health and safety obligations rather than a single fixed rule on airflow volumes. The HSE ventilation guidance sets out the principles employers need to meet, and insurers and environmental health officers will expect a properly balanced, commissioned system with records to match.
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