Carbon Monoxide & Gas Heater Safety: The Adelaide Homeowner's Guide

Published 25 April 2026 · Written by Sidney — Licensed Gas Fitter, Pilot Gas Adelaide · 10 min read

TL;DR: Carbon monoxide from a faulty gas heater is colourless, odourless and lethal. In Australia, people die from it every winter. Prevention is simple: service your heater by a licensed gas fitter every 1–2 years, fit a CO alarm, and know the symptoms (headache, nausea, drowsiness that eases when you leave the house).

Safety warning: If anyone in your home is currently experiencing headache, nausea, dizziness or drowsiness that eases when they step outside, treat it as carbon monoxide poisoning. Turn the heater off at the isolation valve, open doors and windows, leave the house, ring 000 or seek urgent medical help, then ring a gas fitter. Do not use the heater until it has been inspected.

What is carbon monoxide, actually?

Carbon monoxide (CO) is a gas produced when a fuel — natural gas, LPG, petrol, wood, kero — burns without enough oxygen. Every combustion appliance makes a little bit. In a healthy gas heater, it goes up the flue and out of the house at a concentration that's harmless.

The problem: CO is colourless, odourless, tasteless. Your nose can't detect it. Your eyes can't see it. By the time you feel unwell, you've already inhaled enough to affect your blood.

Once in the bloodstream, CO binds to haemoglobin 200 times more readily than oxygen. Your red blood cells stop carrying oxygen. At low doses you get a headache and nausea. At higher doses, you lose consciousness. At higher still, you die — usually in your sleep, which is why it's sometimes called "the silent killer."

How gas heaters leak CO

A working gas heater sends all combustion gases up a sealed flue and outside. CO leaks into your living space in four main ways:

1. Cracked heat exchanger. Inside the heater, the heat exchanger separates combustion air from the warm air that blows into your room. A crack — common on older Vulcan, Pyrox and early Braemar units — lets CO mix with your indoor air.
2. Blocked or damaged flue. Bird nests, rust-through, disconnected flue sections, or a flue cowl buried in leaves all back-push combustion gas into the house. Adelaide's gum trees are merciless for this.
3. Poor combustion. A dirty burner or wrong gas pressure causes incomplete combustion, which dramatically raises CO output. Spot it by yellow or orange flames.
4. Lack of room ventilation on older non-flued units. These have been phased out for new installs but still exist in older homes. If you've got one, get it replaced.

All four of these are picked up in a proper service. Every single one of them is preventable.

Symptoms of CO poisoning

Early symptoms are easy to miss because they mimic a cold, flu, or migraine:

• Headache (often described as dull, pressing)
• Nausea or vomiting
• Dizziness or light-headedness
• Shortness of breath
• Drowsiness, brain fog, trouble concentrating
• Chest tightness

The tell: symptoms improve when you leave the house and come back when you return. Multiple people in the same house getting sick at the same time. Pets acting off — small animals collapse faster than humans.

Severe symptoms: confusion, fainting, seizures, unconsciousness. If someone shows these, get them outside immediately and call 000.

How to detect carbon monoxide

Three ways:

1. A CO alarm. $40 to $120 from Bunnings or any hardware shop. Every Adelaide home with a gas heater should have one.
2. Combustion analysis during a service. Our calibrated analyser measures CO in parts-per-million at the flue exit and in the room. Anything above 30 ppm indoor is a problem.
3. Symptoms. The worst detector — by the time you notice, you've been exposed. Don't rely on this.

Choosing and installing a CO alarm

Look for:

• AS/NZS 4913 compliance (Australian standard for CO alarms). Check the box.
• Digital display showing current PPM reading — more useful than a simple beeper.
• 7- or 10-year sealed lithium battery. Never buy a 9V-battery CO alarm — you'll forget to change it.
• End-of-life warning — alarms wear out at 5–10 years and stop detecting reliably.

Where to install:

• On the wall at eye level, within 3–5 metres of the heater but not directly above or beside it
• In bedrooms or hallways leading to bedrooms — CO can accumulate while you sleep
• Not in bathrooms, kitchens, or within 1m of doors/windows (false alarms and delayed detection)
• Not behind curtains or furniture

Test monthly. Replace per manufacturer recommendation (usually 7–10 years). Write the install date on the back with a permanent marker.

CO prevention checklist

• Service your gas heater every 1–2 years by a licensed gas fitter. See our service frequency guide.
• Fit and maintain a CO alarm compliant with AS/NZS 4913.
• Never use outdoor gas appliances (BBQs, patio heaters, camping stoves) inside the house. This is a leading cause of CO deaths in Australia.
• Never block vents or flue openings to "stop draughts." Those draughts are keeping you alive.
• Don't use your gas oven or cooktop as a space heater. It's not designed to run long hours and produces more CO than a heater.
• Check the flue cowl outside once a year — clear cobwebs, leaves and nests.
• Replace old non-flued gas heaters. If your heater has no flue to the outside and is more than a decade old, budget for replacement.
• Learn the symptoms. Make sure everyone in the house knows them.
• Watch the flame. Blue is good. Yellow or orange means book a fitter.
• Know your isolation valve location. Test you can turn it off by hand.

If you suspect a CO leak — step by step

1. Turn off the heater — use the thermostat first, then the isolation valve at the unit.
2. Open doors and windows — get fresh air flowing.
3. Leave the house. Everyone, including pets.
4. If anyone is symptomatic, ring 000. Tell them suspected CO exposure.
5. Ring the emergency gas line 1800 427 532 if you smell gas as well.
6. Don't go back inside until the house has ventilated and a gas fitter has inspected the heater.
7. Ring a licensed gas fitter for inspection. We run emergency response — see our gas heater emergency guide.

Who's most at risk in Adelaide

CO affects everyone, but these groups need more vigilance:

• Older homes — pre-1990 builds often have older wall furnaces with corroded heat exchangers
• Homes with old non-flued heaters — some still exist in rental stock
• Families with young children — kids absorb CO faster and often can't describe symptoms
• Elderly residents — confuse CO symptoms with general tiredness or existing conditions
• People with heart or lung conditions — affected at lower CO concentrations
• Pregnant women — CO crosses the placenta and affects the foetus before the mother feels symptoms

For a full background on gas safety requirements in SA, the SA Department for Energy and Mining publishes the official guidance. Energy Safe Victoria has some of the best public CO resources in the country — worth a read.

FAQ

Can a properly serviced gas heater still leak CO?

Extremely unlikely. A heater that's been serviced within the last 12–24 months, passes combustion analysis, and has an intact flue is safe. The risk comes from un-serviced or damaged heaters.

Is CO heavier or lighter than air?

Almost the same density as air — it mixes through the room evenly. That's why CO alarms can be placed at eye level rather than floor or ceiling.

Will a smoke alarm detect CO?

No. Smoke alarms detect smoke particles. CO alarms detect carbon monoxide. They're different devices — you need both.

Can I test for CO myself?

A CO alarm with digital readout is the best consumer option. Proper combustion testing needs a calibrated analyser, which is part of a professional service.

Does ducted heating cause CO?

All gas heaters can produce CO if they malfunction. Ducted systems actually distribute warm air separately from combustion gas, so a healthy ducted unit is no more dangerous than a wall unit. A faulty one is arguably worse because it blows into every room.