Kitchen staff often notice the room feels thicker with smoke. That heavy, warm air is usually a sign of poor airflow in commercial cooking areas. It rarely fixes itself. Grease, worn parts, poor system design, and overdue kitchen exhaust cleaning are common causes behind this problem.
Ventilation technicians across Brisbane see the same handful of causes again and again. This guide breaks down each cause, so kitchen owners know exactly what to check first, when kitchen exhaust cleaning may be needed, and how to fix poor airflow.
Table of Contents
Why Commercial Cooking Areas Need Adequate Airflow
A commercial kitchen produces heat, grease, and smoke faster than most other workspaces. So, the air has to be replaced constantly. Safe Work Australia names exhaust ventilation as one of the main ways to manage heat risk in kitchens and laundries. Good airflow also protects the building itself.
AS 1668.2, the Australian Standard for mechanical ventilation, sets minimum exhaust rates for kitchens. This is because a blocked or undersized system cannot clear heat and grease fast enough on its own. So, adequate airflow is needed for staff comfort, food safety, and fire compliance.
6 Common Causes of Commercial Kitchen’s Poor Airflow
Most airflow complaints trace back to one of a small number of repeat offenders. The six causes below cover almost every service call a Brisbane kitchen makes about weak airflow.
Grease-Blocked Commercial Kitchen Ductwork
Grease build-up inside the duct is the top reason airflow drops in a busy kitchen. Every service adds a thin layer of grease inside the ductwork. That grease layer thickens over months. This buildup narrows the path air can travel through. The fan then has to work harder for the same result.
Grease buildup inside ventilation ducts also raises fire risk. Australian buildings with mechanical exhaust are required to meet AS 1668.2, the national standard covering kitchen and process exhaust. Leaking duct joints let air escape before it reaches the fan. Excessive bends in the commercial exhaust duct also slow airflow down at every turn.
Clogged Canopy Filters
Filters are the first line of defence, and dirty ones choke airflow fast. Clogged canopy filters reducing airflow is common in high-fry kitchens where grease builds up quickly. Grease can harden on the mesh within days if filters are not cleaned.
Restricted airflow through greasy filters then forces the whole system to strain. A filter that looks shiny on the outside can still be blocked underneath.
Fan and Motor Faults
A failing fan is often the real reason a kitchen feels stuffy. It usually shows up first as a rattling or humming noise. Technicians call this commercial kitchen extraction fan failure.
Low suction from a restaurant exhaust hood is often a fan problem, not a filter problem. A worn extraction fan motor loses power slowly. So, staff may not notice until the kitchen feels warm and smoky. A damaged fan belt in kitchen extraction systems causes the same weak pull. Rooftop fans have it worse. It collects leaves, dust, and grease that block the blades, and stops air from leaving once it gets there.
Undersized Exhaust Systems
An undersized exhaust system for commercial kitchens will always struggle once the kitchen grows. This shortfall is common in older buildings that expanded their cooking line without upgrading extraction. AS 1668.2 sets a minimum exhaust rate of 250 litres per second for every square metre of cooking surface. Poor ventilation design in high-volume kitchens compounds the problem further.
Blocked Make-Up Air
Air has to come in before it can go out. Many kitchens forget this simple rule. Blocked make-up air vents in restaurants stop fresh air from replacing what the exhaust fan removes. This inadequate replacement air in restaurant kitchens makes doors feel heavy and hard to open.
The room then falls into negative air pressure, so the fan pulls harder but does less. AS 1668.2 requires make-up air to replace 65 to 85 per cent of the exhaust airflow.
Hood Fit and Equipment Placement
A hood positioned slightly wrong will never capture smoke properly, no matter how strong the fan is. This is what’s often called incorrect canopy hood installation. It leaves gaps around the edges where smoke escapes into the room instead of the duct.
AS 1668.2 sets minimum hood overhang at 150mm for light cooking, rising to 450mm for heavy cooking. Poorly positioned cooking equipment under the canopy breaks this coverage. Appliances placed too far forward or to the side sit outside the capture zone.
Ways to Fix Poor Airflow Issues
Most airflow problems can be fixed without replacing the whole system. A regular maintenance routine catches small issues before they turn into breakdowns.
- Clean or replace canopy filters weekly, using hot water or a dishwasher cycle for mesh filters,
- Book a professional duct clean regularly to clear grease build-up before it thickens,
- Have a technician check fan belts, bearings, and motor speed each quarter,
- Clear leaves, dust, and debris from rooftop exhaust units after storms or windy weeks,
- Check make-up air vents and dampers aren’t blocked, painted shut, or covered by stock,
- Get an AS 1668.2 compliance check if the kitchen has added equipment since the system was installed,
- Reposition equipment under the canopy so every appliance sits within the capture zone,
- Repair leaking duct joints and reduce unnecessary bends where the layout allows it.
Final Thoughts
Poor airflow rarely comes from one single fault. It usually builds from several small issues working together, from a slightly blocked filter to a fan losing power year by year. Regular checks catch these problems while they are still cheap and simple to fix.
Eco Cleaning Brisbane has serviced commercial kitchen ventilation across Brisbane for more than 20 years. They know exactly where airflow problems tend to start. A proper inspection can save a kitchen from smoke, heat, and downtime.
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