Yes, and it happens in Queensland every winter
Carbon monoxide is produced when gas burns incompletely. A healthy gas heater burns cleanly and either vents its combustion products outside through a flue or produces so little CO that normal room ventilation deals with it. Problems start when the burner is dirty, the flue is blocked or corroded, the room is sealed up tight, or the heater was never designed for indoor use in the first place.
Queensland's mild reputation works against us here. Because heaters only come out for a couple of months a year, they sit in cupboards or run unserviced for years, then get used hard through a cold snap with the windows shut. That is exactly the pattern behind most CO incidents the Queensland gas regulator warns about each winter, and it matches what we see in the field.
Flued, unflued and portable heaters carry different levels of risk
A flued heater sends combustion products outside through a dedicated pipe. If the flue is intact and the unit is serviced, the CO risk indoors is low. The danger case is a damaged, disconnected or blocked flue, which can spill combustion products back into the room without any obvious sign.
An unflued indoor rated heater releases its combustion products into the room by design. These are legal when used to the manufacturer's ventilation requirements, but they depend entirely on fresh air movement. Run one in a small sealed bedroom overnight and you have removed the safety margin the design relies on.
Portable outdoor heaters, barbecues and camping appliances are the highest risk group. They are certified on the assumption of open air dilution. Bringing one inside, including into a closed garage or a tent, is the single most dangerous thing you can do with a gas appliance, and it features in Australian CO fatalities almost every year.
The warning signs worth acting on
| Sign | What it can mean | What to do |
|---|---|---|
| Yellow or floppy flame instead of crisp blue | Incomplete combustion, CO being produced | Stop using the heater, book a licensed gas service |
| Soot marks around the heater or flue | Combustion products spilling into the room | Stop using it, do not run it again until inspected |
| Heavy condensation on windows when heater runs | Combustion products staying in the room | Improve ventilation, get the unit checked |
| Headache, nausea or drowsiness that improves outside | Possible CO exposure | Get everyone into fresh air, seek medical advice, call us before reuse |
| Pilot light that keeps going out | Burner or draught fault | Book a service rather than repeatedly relighting |
| Musty or unusual smell when the heater starts | Dust burn off is normal briefly, persistent smell is not | If it persists beyond the first few minutes, have it checked |
Carbon monoxide itself is odourless and colourless, so never rely on smell. The pattern to watch is symptoms that appear when the heater runs and ease when you leave the house.
A two yearly licensed service is the fix
Gas appliance manufacturers and Australian safety guidance recommend a licensed service at least every two years. As of 2026 our typical guide range is $150 to $200 for an annual or two yearly gas appliance service on the Gold Coast, with the exact price fixed in writing before we start. That covers burner condition and cleaning, gas pressure checks, flue integrity, spillage testing at the draught diverter, and a check for negative pressure effects, which is where exhaust fans or rangehoods pull combustion products back into the room.
That last test matters more than people expect. Modern homes are sealed tighter than the houses these heaters were designed for, and a bathroom fan running in a closed house can be enough to reverse a flue. It is not something you can spot yourself, which is why the test is part of a proper service rather than a visual once over.
What to do right now if you suspect carbon monoxide
Turn the heater off, open windows and doors, and get everyone outside into fresh air. If anyone has symptoms such as headache, dizziness, nausea or confusion, seek medical help and mention carbon monoxide specifically, because the symptoms are easy to mistake for a virus. Do not use the heater again until a licensed gas fitter has tested it. If you can smell gas as well, treat it as a gas leak: shut the gas off at the meter or bottle and call us from outside the house.
Sources: Resources Safety and Health Queensland gas safety guidance; Queensland Health carbon monoxide advice; Petroleum and Gas (Production and Safety) Act 2004 (Qld).
Book a gas heater safety service
If your heater has not been serviced in the last two years, or it is showing any sign in the table above, get it tested before you rely on it this winter. Hills Plumbing & Gas services and repairs gas appliances across the Gold Coast, with all gas work carried out under a Queensland gas work licence and plumbing work covered by QBCC licence 15243081. Call 0472 657 042 or book through our gas fitting service page.