Quick answer
There is no single cleaning interval that is right for every commercial kitchen exhaust system. The safe frequency depends on the cooking process, daily operating hours, grease production, solid-fuel use, system design, previous inspection results and any requirements set by the property owner, insurer, consent authority or approved maintenance documentation.
Inspection frequency is not the same as cleaning frequency. A system may need frequent inspection because it serves high-volume or solid-fuel cooking. Cleaning should be brought forward whenever grease measurements, visible contamination, leakage or system condition show that the current schedule is not controlling risk.
Why cleaning frequency matters
Commercial kitchen exhaust systems collect heat, smoke, particulates, water vapour and grease-laden cooking effluent. Deposits can accumulate in filters, the hood and plenum, ductwork, effluent-treatment equipment and the exhaust fan. If that contamination is not managed, it can increase fire risk, restrict airflow, affect fan performance, create leakage and make future maintenance more difficult.
Food-safety obligations also require food premises, fixtures, fittings and equipment to be kept clean and prevent unacceptable accumulation of grease and other visible matter. That hygiene obligation is related to, but not identical with, the fire-risk and mechanical-maintenance assessment for the exhaust system.
Start with inspection, not a calendar guess
The AIRAH Commercial Kitchen Exhaust Management Best Practice Guide recommends relating inspection frequency to the type and volume of cooking. Its best-practice starting points are:
| Cooking category | Suggested inspection starting point |
|---|---|
| Solid-fuel cooking | Combustion chambers weekly and the wider exhaust system monthly |
| High-volume cooking | Quarterly |
| Moderate-volume cooking | Semi-annually |
| Low-volume cooking | Annually |
These are recommended inspection frequencies from a best-practice guide, not automatic cleaning dates and not a substitute for the requirements applying to a particular site. Seasonal peaks, menu changes, chargrilling, wok cooking, deep frying, equipment faults or historic grease measurements may justify more frequent inspection.
What should determine the next cleaning date?
A defensible schedule combines the site’s minimum requirements with evidence from the system itself. Important inputs include:
- Cooking fuel and process, including solid fuel, chargrilling, wok cooking and deep frying.
- Daily and weekly operating hours, peak seasons and production volume.
- Filter type, condition, fit and operator cleaning routine.
- Grease-thickness measurements taken at representative locations.
- Contamination at bends, horizontal runs, risers, fan inlets, impellers and discharge points.
- Whether all parts of the duct can be safely accessed and inspected.
- Historical cleaning reports and the observed rate of grease build-up.
- Property, facility-management, insurer, council or approval requirements.
AIRAH’s best-practice method recommends using inspection findings and representative grease-thickness measurements to adjust future cleaning frequency. The guide identifies a mean grease deposit of 0.2 mm across the system as a complete-system cleaning trigger and a single measurement of 2 mm as requiring urgent localised cleaning. These are AIRAH best-practice guide values and must be applied by a competent person within the site’s full risk and compliance context.
Filters, hood, ductwork and fan are different tasks
A clean-looking canopy does not establish that the complete exhaust system is clean. Each part has a different function and access requirement.
Grease filters
Filters are intended to capture grease and will accumulate it during normal operation. Operators may need to wash or exchange filters frequently according to cooking load, filter design and manufacturer instructions. Damaged, missing or poorly seated filters can allow contamination to bypass into the plenum and duct.
Hood, gutters and plenum
Visible stainless-steel surfaces, grease gutters and the exhaust plenum should be checked for build-up, leakage and damaged collection arrangements. Cleaning only the face of the hood can leave contamination hidden above the filters.
Ductwork
The duct should be inspected through correctly located access openings. Horizontal sections, bends, transitions and inaccessible areas can accumulate grease differently from the visible hood. A report should identify any section that could not be inspected or cleaned.
Exhaust fan
Grease on the fan inlet, impeller, casing or discharge can affect balance, airflow, vibration and motor load. Cleaning work also needs safe electrical isolation and methods that do not damage the fan, coatings or connected controls.
Signs the current interval may be too long
- Grease is dripping from the hood, plenum, duct joints, fan or roof discharge.
- Filters become heavily loaded well before the scheduled service.
- Smoke or heat is escaping from the hood despite normal appliance operation.
- The fan is noisier, vibrating or drawing abnormal current.
- There is visible grease beyond the filters or at access panels.
- The menu, appliance load, operating hours or cooking fuel has changed.
- Previous reports show areas that were inaccessible or not cleaned.
- No reliable inspection, cleaning or post-clean verification records exist.
Poor extraction is not always a cleaning problem
Belt wear, motor faults, fan selection, duct resistance, replacement-air problems and control settings can produce similar symptoms. Mechanical and airflow diagnosis may be needed before or after specialist cleaning.
What a professional cleaning report should record
A useful post-clean report should identify the system and scope, record what was inspected and cleaned, disclose inaccessible or excluded areas, document representative pre- and post-clean observations or measurements, list defects and recommend the next inspection or cleaning date.
- Hood, filters, plenum, duct route, access panels and fan locations.
- Cleaning methods and the system components included.
- Areas not inspected or cleaned and the reason.
- Grease-thickness or other agreed cleanliness evidence.
- Mechanical damage, leakage, unsafe access or fire-safety concerns.
- Recommended future interval based on the observed accumulation rate.
What venue staff should do between professional cleans
- Follow the filter manufacturer’s washing or replacement instructions.
- Keep filters correctly installed and replace damaged units.
- Empty and clean grease trays or collection devices before they overflow.
- Record unusual smoke, odour, noise, vibration or leakage.
- Do not enter ductwork or dismantle fans without the correct isolation, access and competence.
- Keep inspection, cleaning, maintenance and airflow-test records together.
- Reassess the schedule when appliances, menu, fuel or operating hours change.
How Altruism NSW can help
Altruism NSW does not provide grease-cleaning services. We can inspect accessible mechanical and electrical exhaust equipment, assess fan and motor condition, identify airflow or control faults, review available cleaning and maintenance records, and recommend when a specialist commercial kitchen exhaust cleaning contractor should be engaged.
After cleaning, Altruism NSW can investigate continued poor capture, undertake commercial kitchen airflow testing where included in the agreed scope, and prioritise fan, motor, belt, VFD, control or replacement-air issues.
Frequently asked questions
Is annual cleaning enough for every commercial kitchen?
No. Annual cleaning may be too infrequent for high-volume, grease-heavy or solid-fuel cooking, while a low-volume system may be managed differently. Start with applicable minimum requirements, then adjust the schedule using inspection findings, operating hours and evidence of grease accumulation.
How often should grease filters be cleaned?
Filters should be washed, exchanged or replaced often enough to prevent excessive loading and bypass. The correct interval depends on cooking duty, filter type and manufacturer instructions and may be much shorter than the whole-system cleaning interval.
Does AS 1668 set the cleaning frequency?
AS 1668 is central to kitchen exhaust design and operation, but a universal cleaning interval should not be attributed to it. Maintenance guidance, including AS 1851 where applicable, the AIRAH best-practice guide, site documentation and stakeholder requirements should be considered together. See our plain-English AS 1668 commercial kitchen compliance guide for more context.
Can Altruism NSW clean the duct and canopy?
No. Grease cleaning should be completed by a suitable specialist commercial kitchen exhaust cleaning contractor. Altruism NSW can assist with inspections, airflow testing and mechanical or electrical faults before or after that work.
What information should we send before an inspection?
Provide the appliance schedule, operating hours, cooking processes, previous cleaning and inspection reports, photographs, known access limitations, fan details and any complaints about smoke, heat, odour, noise or leakage.
Sources
- AIRAH Commercial Kitchen Exhaust Management Best Practice Guide 2022
- Food Standards Australia New Zealand: Cleaning and sanitising
- Standards Australia: AS 1851 catalogue information
This article provides general information only and is not engineering, certification, legal, fire-safety or insurance advice. Requirements must be confirmed for the specific building, approval, system, insurer and agreed scope.