Commercial Kitchen Ventilation Systems

What problem it solves

An industrial kitchen is one of the rare environments that produce high heat, heavy humidity, grease vapour and odour at the same time in an enclosed space. If these four are not handled together, the result is familiar: temperatures nobody can work in, condensation on ceilings and walls, a sticky grease film on every surface and odour spreading into neighbouring rooms.

The job of ventilation is to capture this load at source, exhaust it and replace it with controlled fresh air. What really sets kitchen ventilation apart from other systems is fire safety. Grease that builds up in the hood and exhaust duct is a layer of combustible fuel. A flame over a cooker can travel through an uncleaned duct to another part of the building. That is why a kitchen exhaust system is built with the fire risk in mind, from design through to the cleaning plan.

Applications

• Hotel, hospital and factory canteens
• Large-scale catering production facilities
• Restaurants and shopping centre food courts
• School and dormitory kitchens
• Bakery and pastry production areas
• Ready meal and frozen food production

System components

Canopy hood

Placed over cookers and ovens so that the steam and grease they produce are captured before they spread. The hood must overhang the cooking equipment on every side; insufficient overhang lets steam escape at the edges. It is made from stainless steel, without corners and with a slope that collects the grease flow.

Grease filters

Stainless baffle filters inside the hood capture grease droplets by impact and change of direction. The captured grease runs into the gutter below the filter and collects in a container. These filters must be dishwasher-washable; a filter that cannot be washed does not get washed, and an unwashed filter lets grease into the duct.

Exhaust duct

The duct is designed so it can be cleaned when grease builds up: cleaning hatches are left at intervals and horizontal runs are given a slight fall in the direction of flow. Duct joints must be airtight; a leaking kitchen duct leads to grease building up in the suspended ceiling.

Fresh air unit

If the air exhausted from the kitchen is not replaced with fresh air, the room falls into negative pressure. The visible results are doors that are hard to open, reduced hood efficiency, cold draughts through doors and windows in winter and disturbed flue draught on gas appliances. Fresh air is usually supplied from the service side of the kitchen, at low velocity and without blowing directly onto the work area.

Odour control

The exhaust outlet is placed away from neighbouring windows and the fresh air intake. Where the layout does not allow this, activated carbon after the particle filter, or ozone/UV-based solutions, are considered. All of these units need regular maintenance; an unmaintained odour control unit is the same as having none.

Air balance

Keeping the kitchen slightly negative is a deliberate choice: it stops odour from reaching the dining room. But if the difference is overdone, doors become heavy and flue draught is disturbed; the balance is set by measurement.

Points to watch

Fire dampers and suppression. Where the kitchen exhaust duct passes through fire compartments, dampers are required. In kitchens with automatic suppression over the cooking line, what the exhaust fan does when suppression is triggered must be defined in the scenario.

Access for duct cleaning. Cleaning hatches must be left accessible under the suspended ceiling. An inaccessible hatch means cleaning that never happens.

Noise. Kitchen exhaust fans run at high airflow. The fan is placed on the roof or in a separate space where possible, and silencers are used on the duct.

Material choice. The hood and every surface in contact with grease must be stainless steel. Galvanised sheet corrodes over time in contact with grease and cleaning chemicals.

Periodic cleaning

Kitchen ventilation is not truly handed over without a cleaning plan. Filters are washed frequently by the kitchen team; the hood interior and grease gutter are wiped regularly; the exhaust duct and fan are cleaned at set intervals by a specialist team.

Cleaning frequency depends on how intensively the kitchen is used and how food is cooked. In a kitchen dominated by frying, the duct gets greasy much faster. Keeping a photographic record after each cleaning helps in both fire inspections and insurance processes.

What changes with the type of kitchen

Not every kitchen produces the same load. The cooking method directly determines the size of the ventilation and the choice of filters.

Kitchens focused on frying and grilling have the highest grease load. Hood filters are washed more often, the duct gets dirty faster and odour control often becomes necessary. Exhaust airflow in these kitchens is kept significantly higher than in others.

Kitchens focused on steaming and boiling carry mainly a humidity load. Grease build-up is low but the risk of condensation is high; horizontal duct runs need a fall and condensation measures are needed at the ceiling.

Oven and bakery production has a constant, high heat load but a low grease load. What matters here is keeping the room temperature under control; the fresh air unit and, if needed, cooling come in.

The dishwashing area is often forgotten. Heavy steam forms around the dishwasher; without a separate hood or local extraction, this humidity spreads through the whole kitchen and causes condensation on the ceiling.

Commissioning measurements

At handover the following are measured and recorded: capture velocity at each hood opening, total exhaust and fresh air airflow, the pressure difference between the kitchen and neighbouring rooms, room sound level and fan current values.

The capture velocity measurement is particularly important. If the velocity measured at the edge of the hood is insufficient, steam escapes at the edge; you can see it, but once it is recorded as a number there is no argument about where the problem is.

A common question: can an existing kitchen be upgraded?

Usually yes. If the existing hood is sound, the system can be made to work by changing the filter type, measuring the exhaust airflow and renewing the fan, and adding the missing fresh air unit. The most commonly missing item is the fresh air unit; most kitchens have exhaust but no system to replace the air.