A gas hob flame that lifts away from the burner — sometimes called flame lift or blow-off — is a sign that the gas-to-air mixture is out of balance, or that gas pressure is too high. While some causes are simple to address yourself, others involve the gas supply or appliance internals and must be handled by a licensed gasfitter. Here's what you need to know.
What Does Flame Lift Actually Mean?
A healthy gas burner produces a steady, blue flame that sits right on the burner ports. When the flame lifts off and hovers above the burner head — or even extinguishes itself — it usually means one of the following:
- Too much gas is flowing (high gas pressure or a faulty regulator)
- Too much primary air is being drawn into the burner
- The burner ports are damaged or incorrectly assembled
- The wrong type of gas is being used for the appliance's settings
Occasionally a small amount of lift is normal at very high settings, but persistent lift at normal cooking temperatures is worth investigating.
Common Causes of Flame Lift
1. High Gas Pressure
If the gas pressure coming to your hob is higher than the appliance is rated for, too much gas exits the burner ports and the flame can't anchor itself. Gas pressure is set by a regulator on your LPG cylinder or at the meter for natural gas (reticulated gas). Pressure problems must be diagnosed and fixed by a licensed gasfitter — this is restricted work under the Gas Act 1992.
2. Incorrect Gas Type Setting
Gas hobs are factory-set for either natural gas (NG) or LPG. If your hob has been connected to a different gas type without being converted using the correct jet kit, the flame behaviour will be wrong — including lift. Check your appliance manual or the label on the hob to confirm it matches your gas supply.
3. Burner Cap Misalignment
This is one of the most common — and easiest — DIY fixes. After cleaning or cooking a boil-over, the burner cap (the flat disc sitting on top of the burner head) can be replaced slightly off-centre or upside down. This disrupts airflow and causes uneven or lifting flames.
What you can do: Remove the burner cap and head, check for any obvious damage, and reseat them carefully so they sit flat and level. Refer to your hob's manual for the correct orientation.
4. Blocked or Damaged Burner Ports
Food debris, grease, or corrosion can partially block the small holes (ports) around the burner head. Paradoxically, partial blockages can increase velocity through the remaining open ports, causing lift.
What you can do: With the hob cool and off at the isolation valve, remove the burner head and gently clean the ports with a soft brush or a toothpick. Never use steel wool or sharp metal objects that could enlarge the ports.
5. Draughts and Ventilation
Strong airflow across the hob — from a rangehood on high, an open window, or a nearby extractor fan — can physically push the flame off the burner. Try reducing rangehood speed or closing nearby windows to see if the flame stabilises.
6. Worn or Faulty Injectors
Over time, the small injector (jet) inside the burner can wear and allow more gas through than intended. Replacing injectors is straightforward for a gasfitter but involves working on the gas-carrying parts of the appliance — this is restricted work.
What You Can Safely Check Yourself
| Check | Safe for homeowner? |
|---|---|
| Reseat burner cap and head | ✅ Yes |
| Clean burner ports with a brush | ✅ Yes |
| Reduce rangehood speed / close windows | ✅ Yes |
| Check gas type label matches supply | ✅ Yes (visual check only) |
| Adjust gas pressure regulator | ❌ No — licensed gasfitter only |
| Replace injectors or jets | ❌ No — licensed gasfitter only |
| Reconnect or modify gas pipework | ❌ No — licensed gasfitter only |
Safety First
Never ignore a flame that repeatedly extinguishes itself. An unlit burner still releasing gas is a serious hazard. If you smell gas at any point:
- Turn off the hob and the gas supply at the cylinder or meter.
- Open windows and doors.
- Do not operate any electrical switches.
- Leave the building and call your gas supplier or a licensed gasfitter immediately.
For general gas safety guidance, WorkSafe NZ has useful information on hazardous substances and gas appliance safety.
NZ Regulations and Restricted Work
In New Zealand, work on gas appliances and pipework is restricted work under the Gas Act 1992. Only a gasfitter registered with the Plumbers, Gasfitters and Drainlayers Board (PGDB) is legally allowed to carry out this work. This includes adjusting regulators, replacing injectors, converting appliances between gas types, and any work on gas connections.
Always ask to see your gasfitter's current practising licence before work begins. You can verify a licence on the PGDB website.
When to Call a Professional
Call a licensed gasfitter if:
- Flame lift persists after you've reseated the burner cap and cleaned the ports
- You suspect the appliance is connected to the wrong gas type
- The flame lifts on all burners, not just one (suggests a pressure issue)
- You notice any smell of gas
- The hob is older and hasn't been serviced in several years
- You're unsure of anything at all — gas appliances are not worth guessing with
You can find qualified, local gasfitters on tradedirectory.co.nz.
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