Signs You Need Ducted Heating Service Before Winter

A ducted heating system rarely fails without warning — it drops hints for weeks first, usually in the smells, sounds and uneven rooms that are easy to put up with until the morning it will not start at all. Some of those hints are about comfort and running cost. One of them — the state of a gas unit’s heat exchanger — is about safety. Here are the signs worth acting on, and why the gas service side of this is not optional.

The signs your system is asking for attention

A burning smell at start-up is the classic. A brief version on the first cold morning of the season is just dust burning off the heat exchanger; a version that returns every time the system runs means there is enough build-up in the unit and ducts to keep feeding it. A musty smell is different — that is the odour of the ductwork itself, picked up by the airstream and delivered to every room in the house.

Airflow tells its own story. Rooms that used to warm evenly and now lag behind, outlets that deliver noticeably less air than they did, or a system that runs longer to reach the same thermostat setting all point to restriction somewhere between the fan and the rooms — crushed or leaking ducts, blocked returns or build-up along the runs. Visible dust puffing from the outlets on start-up, or dust settling unusually fast around the vents, says the ducts are carrying more than air.

Then there is behaviour: a unit that fires up, runs briefly and shuts down again — short cycling — or one that becomes noticeably noisier, or gas bills creeping up against the same weather. Each of these is the system compensating for something, and compensation always costs money before it costs the system.

The return air grille deserves its own mention, because it is the one part of the system every household can check in thirty seconds. A return grille matted with dust is starving the whole system of airflow — and everything caught on it has been pulled from the air of your home. If the grille looks grey and felted, the ducts behind it are rarely in better condition.

The carbon monoxide question

Ducted gas heating has one safety consideration that separates it from every comfort issue above. The unit burns gas, and the design keeps combustion products completely separate from the air blown into your rooms. The component responsible for that separation is the heat exchanger — and if it cracks or corrodes through age, combustion gases, including carbon monoxide, can enter the airstream that the system then distributes to the whole house.

Carbon monoxide is colourless and odourless, which is precisely why this is a testing job rather than a judgement call. Victoria’s gas safety guidance is that gas heaters should be serviced at least every two years by a licensed gasfitter, and that service includes testing the unit for carbon monoxide spillage and inspecting the heat exchanger. No smell, sound or performance sign reliably announces this problem — the two-year interval is the protection.

A carbon monoxide alarm in the home is a sensible backstop, but it is the second line of defence, not the first. The service prevents; the alarm only warns.

Two jobs, one system

A complete pre-winter routine for ducted heating is really two pieces of work, done by different specialists. The gas service covers the unit itself: burner, heat exchanger, gas pressures, controls and the safety testing above. It is licensed work, and it is about making the heat safely.

Duct cleaning covers everything after the unit: the metres of ductwork under the floor or in the roof, the outlets in every room and the return air path. It is about what the heat travels through — and after years of service, that ductwork is typically lined with dust, fibres, insect debris and whatever has entered through gaps in the runs. Every hour the heating runs, air passes over all of it on the way to your rooms.

The two jobs solve different problems, and neither substitutes for the other. A freshly serviced unit pushing air through filthy ducts still delivers dusty, musty air badly; freshly cleaned ducts fed by an unserviced unit still carry the safety question. Booked together, they cover the system end to end.

Why dirty ducts undo a good heater

It is worth being specific about what duct build-up does, because it is invisible by nature. Restriction is the first effect: debris along the runs and at the outlets narrows the effective duct, so the fan pushes against more resistance and less air arrives in the rooms — the far ends of the house feel it first. Contamination is the second: the airstream picks up fine dust from the duct walls and redistributes it, which is why some homes find every surface needs dusting again days after the heating season starts. And where floor ducts have gaps or damage, the system can draw from under the house — pulling in damp, musty subfloor air and the smell that comes with it.

None of this is repaired by running the system harder. It is all reversed by cleaning the ductwork, which is exactly why airflow and smell are the two most honest indicators on the list.

Getting ahead of the season

The middle of a cold snap is the worst time to discover any of this — it is when breakdowns peak, when technicians are busiest, and when a house without heating is hardest to live in. The signs above are the early-warning system: act on them while they are still symptoms rather than failures. If the smells, the airflow or the bills have changed — or if the two-year service interval has quietly lapsed — the week you notice is the right week to book. A split system in the living room can carry a house for an evening; it cannot replace the whole-home system winter actually relies on.

Frequently asked questions

Is a burning smell normal when I first turn on the heating?

A brief dusty smell on the first run of the season is common — it is the summer’s dust burning off the heat exchanger and duct surfaces. It should clear within the first use. A burning smell that persists, returns every time the unit runs, or is accompanied by visible dust from the outlets points at build-up in the system that needs attention rather than tolerance.

How often should a ducted gas heater be serviced?

Victorian gas safety guidance is to have gas heaters serviced by a licensed gasfitter at least once every two years. That interval exists because the critical checks — the condition of the heat exchanger and testing for carbon monoxide spillage — cannot be done by looking at the unit from the outside. If you cannot remember the last service, that is the answer.

What does duct cleaning have to do with heating performance?

The ducts are the delivery system: every litre of warm air the unit produces travels through them. Ducts lined with years of dust and debris narrow the airflow, feed dust into every room each time the heating runs, and make the unit work longer to reach the same temperature. Cleaning the ductwork restores the airflow the system was designed around, and it is a separate job from the gas service — a complete pre-winter routine includes both.

Do I need a carbon monoxide alarm if the heater is serviced?

An alarm is a worthwhile backstop, but it is not a substitute for servicing. The service is what verifies the heat exchanger is sound and the unit is not spilling combustion products in the first place; an alarm only tells you after something has already gone wrong. Treat the two-yearly service as the primary control and the alarm as the safety net behind it.