Heating, cooling and gas safety: systems, servicing and carbon monoxide
Identify each system first: split systems and ducted reverse-cycle, ducted gas, gas space heaters, hydronic, wood heaters and evaporative coolers each need different care. Energy Safe Victoria recommends every gas heater be serviced at least every two years by a qualified gasfitter, including a carbon monoxide spillage test. Open-flued gas heaters, which draw air from the room, can spill carbon monoxide if exhaust fans run at the same time or the room lacks ventilation. Carbon monoxide is colourless and odourless, so headaches, nausea or dizziness that ease away from home deserve attention. An alarm is a backup, never a substitute for servicing.
- 01ServiceGas heaters at least every two years, with a spillage test
- 02VentilateNo exhaust fans while an open-flued heater runs
- 03BackupA carbon monoxide alarm warns; it does not prevent
Carbon monoxide has no colour and no smell.
What you'll notice
Heating and cooling faults usually show up as changes in comfort, sound or smell. Some gas warning signs are urgent; treat them that way.
| Sense | Sign | What to do |
|---|---|---|
| Feel | Headaches, nausea, dizziness or drowsiness that ease when you leave the house | Turn the heater off, ventilate, get fresh air and seek medical advice; then have the heater checked |
| See | A yellow or orange gas flame, soot or scorch marks around a heater or flue | Stop using it until a gasfitter has inspected it |
| Smell | Gas | Turn appliances off, avoid switches and flames, ventilate, leave and call your gas emergency line |
| See | A pilot light that keeps going out, or condensation and staining around a heater | Have it serviced; see gas heaters |
| Hear | Rattling, grinding or new noises from a split system or ducted unit | Systems and servicing |
| Feel | Uneven temperatures, weak airflow from vents, or a system that runs constantly | Filters, ducts or refrigerant; see systems and servicing |
| Smell | Musty air from vents or a split system when it starts | Dirty filters or coils, or moisture in ducts; see damp |
Systems and servicing
| System | How it works | What to check and service |
|---|---|---|
| Split system (reverse-cycle) | An indoor unit and outdoor heat pump heat and cool one area | Clean filters every few months; keep the outdoor unit clear; professional service as the manufacturer recommends |
| Ducted reverse-cycle | One heat pump serves the house through ducts in the roof or floor | Filters, duct condition and insulation, zone controls, outdoor unit clearance |
| Ducted gas heating | A gas furnace heats air and pushes it through ducts | Gas service at least every two years, including the heat exchanger and a carbon monoxide test |
| Gas space heater (wall or freestanding) | Heats one room; may be room-sealed, open-flued or flueless | Gas service at least every two years; know which type it is |
| Hydronic | A boiler heats water piped to radiators or under the floor | Boiler service, pressure, leaks at radiators and valves |
| Wood heater or open fire | Burns wood, venting through a flue or chimney | Annual flue cleaning, dry fuel, clearances to combustibles |
| Evaporative cooler | Cools by evaporating water, usually from a roof unit | Seasonal service, pads, water supply and drainage, roof penetration seals |
Ask for service records for every system when buying, and note its age from the compliance plate. Old systems are not automatically unsafe or inefficient, but a ducted gas heater or split system with no service history deserves a check before you rely on it.
Gas heaters and carbon monoxide
Energy Safe Victoria warns that all gas heaters can spill or leak carbon monoxide, and that spillage can be lethal. It recommends that every gas space heater, central heater and gas water heater be serviced at least every two years by a qualified gasfitter, and Victoria's Department of Health gives the same advice for central heating, wall units and gas log fires.
| Type | Where it gets its air | What to know |
|---|---|---|
| Room-sealed | From outside, through a sealed flue | Not affected by room ventilation or exhaust fans; Energy Safe Victoria recommends this type |
| Open-flued | From the room, venting through a flue in the ceiling or wall | Can spill carbon monoxide into the room under negative pressure; needs room ventilation and no exhaust fans running |
| Flueless (unflued) | From the room, venting into the room | Needs generous ventilation; rules on their use vary by state |
Negative pressure is the key risk. When a rangehood, bathroom fan or toilet fan runs in a well-sealed home, it can pull air down an open-flued heater's flue and draw carbon monoxide back into the room. Energy Safe Victoria advises not running exhaust fans while an open-flued heater is on, and keeping some ventilation in the room. Since 1 August 2022, any open-flued gas space heater sold or installed in Victoria must shut down automatically if it starts spilling. Ask your gasfitter whether your heater is open-flued, and whether it has that protection.
A service should include a negative pressure and combustion spillage test, not only a clean. Victoria's Department of Health has warned specifically against using Vulcan Heritage or Pyrox Heritage gas heaters until they have been tested and serviced.
Carbon monoxide alarms
Because carbon monoxide has no colour or smell, a carbon monoxide alarm is a sensible backup in homes with gas or wood heating. It is not a substitute for servicing: an alarm warns once carbon monoxide is present, while servicing stops it being produced. Fit it to the manufacturer's instructions and replace it at the end of its stated life.
What to ask before you buy or rent
Ask which heating and cooling systems the home has, their ages, and the date and findings of the last gas service, including whether a carbon monoxide test was done. A standard building inspection does not test gas appliances. For older homes, check gas heaters and flues alongside the wiring in the switchboards guide, and pair heating with a working smoke alarm system from the fire safety guide.
Common misreads
| What people say | What is closer to right |
|---|---|
| "It lights and gets warm, so it is fine" | A heater can run while spilling carbon monoxide. Only a gasfitter's spillage test shows it. |
| "A carbon monoxide alarm means I can skip servicing" | The alarm is a backup. Servicing at least every two years prevents the problem. |
| "Sealing up draughts is always good" | In a home with an open-flued heater, sealing without ventilation can raise the carbon monoxide risk. |
| "Ducted heating vents are just dusty" | Musty vents can mean moisture in ducts or dirty coils; have the system checked. |
Worked example: a draught-proofed house with an old wall heater
Illustrative reasoning example, not an inspected property. An owner has draught-sealed a 1970s house to save energy. The living room has a 1990s gas wall heater with a flue through the ceiling, and a new powerful rangehood in the open kitchen. Family members have had headaches on cold evenings.
The heater is likely open-flued, the house is now tighter, and the rangehood can create negative pressure. The immediate step is to stop using the heater and the rangehood together, ventilate, and see a doctor about the symptoms. Then a gasfitter carries out a negative pressure and spillage test and advises on ventilation, repair or replacing it with a room-sealed heater or reverse-cycle system. See insulation, ventilation and condensation for balancing a tighter home.
Frequently asked questions
How often should a gas heater be serviced?
Energy Safe Victoria recommends every gas heater, including central heaters and gas water heaters, be serviced at least every two years by a qualified gasfitter, with a carbon monoxide spillage test.
What is an open-flued gas heater?
A gas heater that draws its combustion air from the room and vents through a flue in the ceiling or wall. It can spill carbon monoxide into the room if exhaust fans run or the room lacks ventilation. A gasfitter can tell you which type you have.
Can exhaust fans cause carbon monoxide poisoning?
They can contribute. Rangehoods and bathroom or toilet fans can create negative pressure that draws carbon monoxide from an open-flued heater back into the room. Do not run them while an open-flued heater is on.
What are the symptoms of carbon monoxide poisoning?
Headaches, nausea, dizziness, tiredness and flu-like symptoms, often easing when you leave the house. Turn the heater off, ventilate, get fresh air and seek medical advice.
Do I need a carbon monoxide alarm?
It is a sensible backup in homes with gas or wood heating, but it does not replace servicing at least every two years.
How often should I clean split system filters?
Every few months during regular use, or as the manufacturer recommends. Dirty filters reduce airflow and efficiency and can cause musty smells.
Does a building inspection check the heating?
Not in any depth. A standard inspection does not test gas appliances or air-conditioning. Ask for service records and use a licensed gasfitter or technician.
How this guide was researched
We start from what owners notice, identify each system type and its servicing, then set out the gas heater types, negative pressure and carbon monoxide risk, with a fictional example.
Limits: Servicing advice and the 2022 open-flued requirement are Victorian; other states differ. All gas work must be done by a licensed gasfitter.
Sources
- Heating your home with gasEnergy Safe Victoria · accessed
- Open-flued gas heaters and ventilationEnergy Safe Victoria · accessed
- Carbon monoxide poisoning in the homeVictorian Department of Health · accessed
- Open-flued gas space heaters must meet new standardsPlumbing Connection · accessed
- Repairs and maintenanceYourHome, Australian Government · accessed