What Are the Signs of a Faulty or Dangerous Gas Appliance?

Gas appliances make life comfortable — from hot showers to warm living rooms — but a faulty one can be genuinely dangerous. Carbon monoxide poisoning, gas leaks, and fires are all real risks when something goes wrong. Knowing the warning signs early could save your life or the lives of your whānau.

The Most Serious Warning Signs

Some signs demand immediate action. If you notice any of the following, stop using the appliance, ventilate the area, and call a licensed gasfitter or your gas retailer straight away:

• Smell of gas — Natural gas has a distinctive rotten-egg odour added specifically so you can detect leaks. If you smell gas near an appliance or anywhere in your home, do not switch any lights or appliances on or off, and leave the building immediately.
• Yellow or orange flames instead of a clean blue flame on a burner or hob. This indicates incomplete combustion, which produces carbon monoxide.
• Black soot or scorch marks around or above an appliance — a sign of incomplete combustion or a flue problem.
• Pilot light that keeps going out repeatedly, which may indicate a faulty thermocouple or gas pressure issue.
• Unusual smells when the appliance is running — a faint burning or acrid smell that isn't food or dust burning off.

Signs of Carbon Monoxide Problems

Carbon monoxide (CO) is odourless and colourless, making it especially dangerous. It's produced when gas doesn't burn completely. Warning signs that CO may be present include:

• Headaches, dizziness, nausea, or confusion that improve when you leave the house
• Multiple household members (or pets) feeling unwell at the same time
• Condensation or staining on walls near a gas appliance
• A CO alarm sounding — if you don't have one, WorkSafe NZ strongly recommends fitting one in any home with gas appliances

If you suspect CO, get everyone out of the house immediately and call 111.

Visual and Performance Warning Signs

Not every sign is an emergency, but these should still prompt a call to a professional:

• Appliance takes longer than usual to heat up or doesn't reach the right temperature
• Unusual noises — banging, popping, or hissing from a gas heater, hot water cylinder, or hob
• Flame lifts off the burner or blows out easily in normal conditions
• Visible rust, corrosion, or physical damage to the appliance body, gas connections, or flue
• Flexible gas hoses that are cracked, kinked, or older than their recommended service life
• Water heater producing discoloured or smelly hot water, which can indicate internal corrosion

Flue and Ventilation Issues

Many gas appliances — particularly older unflued heaters — rely on adequate ventilation to operate safely. BRANZ research has highlighted that unflued gas heaters can raise indoor moisture and pollutant levels significantly. Signs of a flue or ventilation problem include:

• Excessive condensation on windows when the heater is running
• Backdrafting — where combustion gases are drawn back into the room rather than venting outside
• Visible damage, blockage, or disconnection in the flue pipe
• Birds' nests or debris blocking an external flue terminal

Under the NZ Building Code clause G12, gas installations must meet specific requirements for combustion air and flue discharge. If your appliance was installed some time ago, it's worth having a licensed gasfitter check it still complies.

What Homeowners Can Safely Check

While gas work itself is restricted work (see below), there are a few things you can safely do yourself:

• Visually inspect flexible hoses for cracking or kinking
• Check that burner flames are blue and stable
• Keep the area around appliances clear of flammable materials
• Test your CO alarm regularly and replace batteries as needed
• Ensure rooms with gas appliances have adequate ventilation (open a window slightly when using an unflued heater)

When to Call a Professional

Under the Gas (Safety and Measurement) Regulations 2010, all gas fitting work is restricted work in New Zealand. This means only a gasfitter licensed by the Plumbers, Gasfitters and Drainlayers Board (PGDB) is legally allowed to:

• Install, repair, alter, or disconnect any gas appliance or pipework
• Test gas lines for leaks
• Service or replace components such as thermocouples, burners, or regulators
• Commission a new appliance or relight a system after a gas outage

Do not attempt to repair a gas appliance yourself, even if the fix seems simple. An incorrect repair can create a serious hazard. If you're a landlord, note that the Healthy Homes Standards require heating appliances to be safe and in good working order.

You can find a qualified, licensed gasfitter in your area through tradedirectory.co.nz.

A Quick Reference: Symptoms and Actions

Sources & Further Reading

• WorkSafe NZ — Carbon Monoxide Safety
• PGDB — Licensed Gasfitters
• MBIE Building Performance — Gas Installations
• BRANZ — Indoor Air Quality and Gas Appliances
• Tenancy Services — Healthy Homes Standards