How Often Should Kitchen Ducts Be Cleaned?

One of the most common questions we get from restaurant owners and building managers is: “How often do my kitchen ducts actually need cleaning?” The short answer is that it depends on your kitchen. The longer answer is what this guide is all about.

Why Regular Cleaning Matters

Grease and carbon build up inside your kitchen extraction system every time you cook. Over time, that buildup creates several serious problems:

• Fire risk. Grease-laden ductwork is highly flammable. A kitchen fire that reaches a greasy duct system can spread rapidly through the building.
• Compliance issues. Your extraction system is a specified system under the Building Act. If it's not properly maintained, you won't pass your 12A inspection — and that means problems with your BWOF.
• Poor hygiene. A dirty system can harbour bacteria and contribute to pest problems. Not ideal in a food preparation environment.
• Reduced efficiency. Blocked or restricted ductwork makes your system work harder, which means higher energy costs and shorter equipment life.

Recommended Cleaning Frequencies

As a general guide, here's how often different types of commercial kitchens should have their extraction systems cleaned:

Heavy-Use Kitchens: Every 3 to 6 Months

This includes busy restaurants, fast food outlets, takeaway shops, and any kitchen that's cooking high volumes of food — especially anything involving deep frying, wok cooking, or chargrilling. These cooking methods produce large amounts of grease-laden vapour, and the system builds up residue quickly.

Moderate-Use Kitchens: Every 6 to 12 Months

Think school cafeterias, corporate kitchens, aged care facilities, and mid-volume restaurants. The cooking isn't as intense or constant, but there's still enough throughput to require regular attention.

Light-Use Kitchens: Every 12 Months

This covers kitchens that are only used occasionally or for light cooking — things like church halls, community centres, and small cafe kitchens that mostly do reheating and light prep work.

These are general guidelines. Your specific situation might require more or less frequent cleaning depending on several factors.

Factors That Affect Cleaning Frequency

Every kitchen is different. Here are the main things that influence how often your system needs attention:

• Cooking volume. The more you cook, the faster grease builds up. A kitchen running two services a day accumulates grease much faster than one running just lunches.
• Type of cooking. Deep frying, chargrilling, and wok cooking produce far more grease and carbon than baking, steaming, or boiling.
• Hours of operation. A kitchen running 16 hours a day will need cleaning more often than one running 8 hours.
• Filter maintenance. If your kitchen staff are regularly cleaning baffle filters, less grease makes it into the ductwork. If filters are neglected, the ducts pick up the slack.
• System design. Some extraction systems are better designed than others. Older or poorly laid-out systems may trap grease more readily and need cleaning more often.

Signs Your Ducts Need Cleaning Now

Don't wait for your next scheduled clean if you notice any of these warning signs:

• Visible grease. If you can see grease dripping from the canopy, around filters, or on duct access panels, the system is overdue for a clean.
• Reduced airflow. If the extraction system isn't pulling air like it used to, grease buildup in the ductwork could be restricting the flow.
• Unpleasant odours. A properly functioning extraction system shouldn't produce lingering cooking smells. If it does, there may be a buildup problem.
• Failed inspection. If your system has failed a 12A inspection, cleaning will likely be the first step toward getting it compliant again.

NZ Compliance Requirements

In New Zealand, your commercial kitchen extraction system is a specified system under the Building Act 2004. That means it needs to be on your building's compliance schedule, inspected by an IQP, and maintained to the required standard.

While the Building Act doesn't specify exact cleaning frequencies, it does require that the system is maintained in a condition that meets its intended performance. In practice, that means keeping it clean enough to pass your 12A inspection and maintain your BWOF.

If your system fails an inspection because of grease buildup, that's a sign your cleaning schedule isn't frequent enough.

Get Your System on a Schedule

The best approach is to set up a regular cleaning schedule based on your kitchen's usage. That way you're never caught out by a failed inspection or a system that's become a fire risk.

At Ductflow, we provide kitchen extract cleaning across Auckland, Hawkes Bay, Bay of Plenty, Gisborne, and the Waikato. We can help you work out the right cleaning frequency for your kitchen and set up a schedule that keeps you compliant all year round.

Get in touch for a no-obligation quote.