Why the alarm matters
Carbon monoxide can't be seen or smelt, and Energy Safe Victoria warns that all gas heaters can spill it. Victoria's Department of Health lists possible symptoms including tiredness, shortness of breath, headaches, dizziness, nausea, weakness, confusion and chest pain. They're easy to put down to a cold or a long day, especially on a cold July night with the heater running.
What can set it off
A gas space heater or gas ducted heater with a blocked flue, a damaged heat exchanger or poor ventilation is the usual suspect. Energy Safe Victoria says open-flued heaters spill carbon monoxide more easily, and that running a rangehood or bathroom exhaust fan while a gas heater is on can draw it into living spaces. A car, petrol mower or generator running in an attached garage can also put carbon monoxide into the house.
Genuine false alarms do happen, usually from a low battery, an alarm at the end of its life or a faulty unit. Many alarms use a different beep pattern for these, and the manual says which is which. Don't assume a full alarm is false. Get out first and work it out afterwards.
Before the heater goes back on
Energy Safe Victoria recommends having gas heaters serviced at least every two years by a qualified gasfitter, including a carbon monoxide spillage test, and says an alarm helps but should never replace servicing. Gas heater servicing and repairs are done by a gasfitter licensed for Type A appliances. Our electricians look after the power supply, controls and fans.
If you rent, tell your rental provider in writing. A gas leak and a failed heating appliance are both urgent repairs. If you'd like a hard-wired carbon monoxide alarm, Energy Safe Victoria says it must be installed by a licensed electrician.
What you can safely do now
- Get everyone outside into fresh air, pets included.
- On the way out, turn off gas heaters and other gas appliances if you can do it quickly and safely.
- Open doors and windows if they're on your way, then stay outside.
- If anyone feels unwell, get medical help straight away and mention carbon monoxide.
- Leave the suspect appliance off until a licensed gasfitter has checked it.
Services that can help
Read more in our guides
Related questions
- My gas heater flame looks different. Is that a problem?Yes, treat it as one.
- Why does my heater smell when I turn it on for the first time in winter?A dusty, slightly burnt smell on the first run of the season is usually dust burning off the heat exchanger, coil or element, and it fades.
- Does my gas ducted heater have a filter I can clean?Many do.
- Who is qualified to do a rental gas safety check?A licensed or registered gasfitter endorsed for Type A gas appliance servicing.
Sources for this answer
4 sources, with the date each was checked
- 1.Energy Safe Victoria: All gas heaters can spill carbon monoxide (CO) – a gas you can’t see or smell that can make you seriously unwell or kill you. Accessed 30 September 2026.
- 2.Department of Health (Victoria): When carbon monoxide is inhaled, it replaces oxygen in the blood, which may cause symptoms including tiredness, shortness of breath, headaches, dizziness, nausea, weakness, confusion or chest pain. Accessed 30 September 2026.
- 3.Energy Safe Victoria: Open-flued heaters can spill carbon monoxide more easily than other types of heaters, making them more dangerous. Accessed 30 September 2026.
- 4.Consumer Affairs Victoria: Anything on this list is legally defined as an urgent repair: burst water service blocked or broken toilet system serious roof leak gas leak dangerous electrical fault flooding or serious flood damage serious… Accessed 30 September 2026.
General information for homes in Victoria. Every installation is different, so treat this as a starting point. Where this answer refers to Victorian safety or rental rules, the sources above have the current requirements.