Restaurant and cafe kitchens are a highly specialised fire risk environment, with the prevalence of open flames, hot surfaces, cooking oil and fats.

Commercial kitchen mechanical exhaust systems are vital for air cleanliness and quality as they work to remove heat, smoke and airborne grease. If they are not installed, maintained or cleaned correctly, they can very quickly change from being a safety feature to a major fire hazard. A fire in the kitchen can quickly spread through the exhaust system, fuelled by accumulated grease, causing substantial building damage. This could be a kitchen in an airport, hospital or multi-storey residential tower.

A fire requires three elements, and a kitchen exhaust system can provide all of them.

1. Fuel: Grease and oil residues accumulate in canopy hoods, ductwork and exhaust fans, creating highly flammable deposits.
2. Ignition Sources: Open flames, overheated appliances and sparking equipment.
3. Oxygen: The ventilation system’s air supply can fuel a fire, turning ducts into conduits for flame and smoke.

Compliance and Standards

The National Construction Code and Australian Standards govern the design, installation, and maintenance of kitchen exhaust systems. Compliance with these standards is essential to minimise fire risks and meet regulatory obligations.

The standards include

• AS/NZS 1668.1 The use of ventilation and air conditioning in buildings, Part 1: Fire and smoke control in buildings. This standard sets out the minimum requirements for the design, construction, installation and commissioning of mechanical and air conditioning systems for fire and smoke control in multi-compartment buildings.
• AS 1668.2 The use of ventilation and air conditioning in buildings, Part 2: Mechanical ventilation in buildings
• AS 1851–2012: Routine Service of Fire Protection Systems and Equipment. This standards sets out requirements for inspection, testing, preventive maintenance and survey of fire protection systems and equipment, which includes kitchen exhaust systems and fire suppression equipment.

Fire Safety

It is not as simple as venting smoke, these systems must also be fire separated with ducts installed at a specific distance from combustible materials or insulated for fire resistance. Grease filters have a minimum distance allowed from heat sources and access panels are mandatory for inspection and cleaning.

The kitchen exhaust system should also supplement the fire protection systems in place. This includes automatic wet chemical systems and correct heat detectors. Wet chemical fire extinguishers and fire blankets should also be available with staff trained on how to use them. This includes knowing what type of fire extinguisher to use for different types of fires.

Cleaning and maintaining the kitchen exhaust system is not just a checkbox in the long list of items to clean in a kitchen. As a smoke exhaust system, it is a type of fire protection equipment and so must follow the strict maintenance schedule outlined in AS 1851-2012.

Legal Liability

Across Australia, fires linked to poorly maintained kitchen exhaust systems cause millions of dollars in property damage every year, most of it preventable. According to AIRAH, ‘the ignition of cooking materials accounts for almost half of all commercial kitchen fires and almost all of these (90 per cent) get into the kitchen hood exhaust system.’ (www.airah.org.au)

Failure to clean and inspect systems regularly, allowing grease to build-up and compromised safety is a maintenance issue. Liability for maintenance can be tricky in multi-tenant buildings, where unclear roles can lead to system neglect. With most establishments hiring contractors to maintain grease filters etc, maintaining records is vital.

Installation defects can include incorrect duct grading and poor sealing which results in inadequate fire separation increase fire risks.

Insurance companies view kitchen exhaust systems as one of the highest-risk elements in a hospitality property. Many policies include strict conditions that require:

• Proof of compliance with AS/NZS 1668.1 design provisions;
• Evidence of AS 1851 servicing and cleaning by qualified professionals;
• Installation and maintenance of automatic fire suppression systems in high-risk areas.

Failure to comply can result in a claim being denied. In some cases, insurers have refused to cover losses when grease build-up or non‑compliant duct design contributed to the fire.

Best Practices for Kitchen Exhaust Fire Safety

1. Design for safety from the outset – Ensure new or upgraded systems meet AS/NZS 1668.1. Vertical ducts are safer than horizontal ducts
2. Follow AS 1851 cleaning and maintenance intervals – Schedule and document all work.
3. Install suppression systems – Use wet chemical systems designed for cooking oil fires.
4. Train all staff – Teach safe cooking practices and emergency response.
5. Inspect between cleans – Regularly check filters, hoods, and visible ducting for grease accumulation.
6. Work with specialists – Use contractors who can provide photographic evidence and full-system reports.

Neglecting kitchen exhaust maintenance doesn’t just put people and property at risk—it can also cost a business its livelihood.

Conclusion

For commercial kitchen operators, prioritising fire safety in exhaust systems is essential. Fires in these systems are both common and potentially devastating—but they are also preventable.

By conducting regular inspections, complying with relevant Australian Standards, and investing in appropriate fire protection systems and equipment, operators can safeguard lives, minimise property damage, and avoid costly business interruptions.

Owners and managers should follow best‑practice cleaning and maintenance protocols, and work closely with qualified professionals to reduce fire risk, protect assets, and meet both insurance and legal obligations. To strengthen future liability protection, all training records, contracts, inspection reports and compliance certificates should be meticulously maintained and readily accessible.