A gas heater can warm your home quietly for years, then show one small warning sign before a serious fault appears.
I've seen households ignore odd smells, soot, or a weak flame until the repair cost doubles or the unit must be replaced.
The biggest risk is carbon monoxide, or CO, a gas you cannot see or smell, so early action matters.
Quick Safety Checks
Five checks can help you spot risk early and respond fast.
Service your heater at least every two years with a licensed gasfitter endorsed for Type A gas appliance servicing.
Yellow flames, soot, or eye and throat irritation are danger signs. They can point to incomplete combustion and possible CO risk.
Sealed homes change airflow. Strong exhaust fans can pull exhaust back inside from open-flued heaters.
CO alarms help, but they do not replace servicing. Choose models certified to EN 50291 or UL 2034.
If you smell gas, act fast. Turn the heater off if safe, ventilate the area, avoid sparks, and call the emergency number on your gas bill or 000.
How Gas Heaters Work in Australian Homes
Your heater type affects how air moves, how exhaust leaves, and how likely fumes are to re-enter the room.
Open-Flued, Room-Sealed, and Unflued
Open-flued heaters draw air from the room for combustion, the process of burning gas, then send exhaust through a flue, the pipe that carries fumes outside. Room-sealed heaters draw air from outside, which makes them less sensitive to fans and draughts. Unflued portable heaters release combustion byproducts into the room, so ventilation is critical.
Why Renovations Change the Risk
Double glazing, weather seals, and strong rangehoods can create negative pressure, which means air is pulled out of the home faster than it comes in. In an open-flued setup, that pressure can drag exhaust gases, including CO, back into living areas.
Ducted Systems
Ducted gas heaters can hide faults because the burner sits out of sight. If the heat exchanger, the metal barrier between exhaust and household air, cracks, fumes can move through the ducts without an obvious warning.
Early Warning Signs Your Heater Needs Attention
Small changes in flame, smell, or comfort usually appear before a major breakdown.
Flame colour: A steady blue flame is normal. Yellow or orange flames with sooty tips suggest incomplete combustion.
Soot marks: Black stains near the unit, on walls, or around vents suggest exhaust is not leaving the home properly.
Ignition trouble: A pilot that will not stay lit, delayed ignition, or short cycling points to failing parts.
Unusual smells: Stale, acrid, or burning odours while the heater runs should never be ignored.
Health symptoms: Headaches, dizziness, nausea, or unusual tiredness that ease when you leave the room may signal CO exposure.
Higher gas bills: If your usage jumps during similar weather, the heater may be working harder than it should.
Simple Safety Steps You Can Do Today
Basic habits lower risk, even when the heater seems to run normally.
Keep vents, grilles, and the flue area clear of furniture, curtains, dust, and storage. For open-flued heaters, avoid using range hoods or bathroom exhaust fans at full speed unless a window is open nearby.
Test CO alarms each month and replace them before the expiry date. Energy Safe Victoria advises choosing alarms certified to EN 50291 or UL 2034 and placing them near sleeping areas.
Keep a one-metre clearance around the heater, and check the Energy Safe Victoria website for model recalls before winter. That quick check can stop you from using a unit with a known fault.
When To Shut It Down Now
Certain warning signs mean the heater should stay off until a licensed gasfitter checks it.
Shut it down right away if you notice a strong gas smell, a CO alarm, visible soot, damaged flue parts, or yellow flames paired with headaches or nausea.
Turn off the appliance.
If it is safe, shut off the gas supply at the meter.
Open windows and doors.
Do not use flames, light switches, or anything that could create a spark.
Call the emergency number on your gas bill.
If anyone feels unwell or you suspect CO exposure, call 000.
When To Call a Licensed Pro
Most heater faults need tools and tests that are not safe or practical for homeowners.
If your heater shows warning signs or a CO alarm has sounded, do not keep using it or assume the problem will pass, because a licensed technician can diagnose combustion faults, test for CO, and confirm the system is safe before you switch it on again. For compliant repairs and clear next steps, book gas heater repair with O'Shea Plumbing.
What a Proper Service Includes
A licensed gasfitter can clean key parts, inspect the flue, test for leaks, and run a CO spillage test, which checks whether exhaust gases spill back into the room. They may also test under negative pressure by running exhaust fans and checking how the appliance behaves.
Who To Hire
Use a licensed gasfitter with an endorsement for Type A gas appliance servicing, the class used for standard household gas appliances. In NSW, Fair Trading oversees gas installation rules that reference AS/NZS 5601.
O'Shea Plumbing handles gas heater servicing and repairs in line with Australian standards.
Keep the Paper Trail
Ask for a written service report after every visit. If a Certificate of Compliance applies in your state, store it with your home records.
Landlords and Property Managers
Rental checks are a legal responsibility, not an optional extra.
In Victoria, rental providers must arrange a gas safety check of all gas installations and fittings at least every two years by a licensed or registered gasfitter. Renters can ask for the date of the last check, so clear records matter.
For renovated rentals, schedule servicing before winter and track recall notices, service dates, and tenant updates in one checklist.
Repair or Replace
Repair is worthwhile only if the unit can be made safe and still suits the way your home is built.
Replacement is usually the better choice if the heater fails a CO or negative-pressure test, has a cracked heat exchanger, or is an older open-flued unit in a tightly sealed home. Victoria stopped the sale and supply of non-compliant open-flued gas space heaters from August 2022.
Safer options include room-sealed gas heaters and reverse-cycle systems. Broader home upgrade and renovation features often pair heating upgrades with insulation, glazing, and draught sealing improvements, which is the same approach worth taking here so the new system does not work harder than it should. If you are already upgrading, review insulation and draught sealing at the same time as the heater swap.
Post-Service Peace of Mind
A repair is not fully done until you confirm the heater keeps running safely at home.
Check for a steady blue flame and ask the technician to test the unit with exhaust fans running at different speeds. Then set a two-year reminder for servicing and test your CO alarms each month.
Keep service reports, warning notices, and photos together. Those records are useful for insurers, property managers, and future buyers.
If the heater behaves oddly or anyone feels unwell while it runs, turn it off and book a licensed inspection.
That quick decision can prevent a health risk, a fire hazard, or a much bigger bill later.
FAQs
These quick answers cover the questions people ask most after they notice a problem.
What Colour Should My Gas Heater Flame Be?
A healthy heater should show a steady blue flame. Persistent yellow, orange, or sooty flames suggest incomplete combustion, so stop using the unit and have it checked.
How Often Should a Gas Heater Be Serviced?
Service it at least every two years by a licensed gasfitter endorsed for Type A gas appliance servicing. Rental properties in Victoria must meet this schedule.
Do I Need a CO Alarm if I Service My Heater Regularly?
Yes. Regular servicing lowers risk, but a CO alarm adds backup between visits. Choose a certified model and install it near sleeping areas.
Is It Safe to Run My Rangehood While an Open-Flued Heater Is On?
Not if the heater is open-flued and the fan is strong. The fan can pull exhaust back inside, so open a nearby window or avoid running both at the same time.
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