Not every duct looks like this. Plenty do.
That’s the inside of a flexible duct pulled out of an ordinary Australian home — dust-laden, damp and mould-streaked. It’s not a worst case; it’s the sort of thing installers find fairly regularly once a duct has been in service a while. Whether your own ducts look anything like it depends on the age of the system, the humidity where you live, and how the home is used.
The inner core of flexible duct is a thin polyester film laminate bonded around a steel wire helix. The film itself is smooth and airtight — but the helix gives the bore a corrugated profile, and dust settles into those convolutions. Add condensation and you have both a food source and the moisture mould needs.
That film is also thin. Duct manufacturers and NADCA both caution that aggressive brushing or air-whipping can tear the inner core — so even on a run you can physically reach, there’s a real limit to how hard it can be cleaned.
In many modern buildings, that ductwork is permanent.
Not every property is built this way — but it’s now very common. On a lot of today’s homes and commercial fit-outs, insulated flexible duct is threaded through the floor and ceiling joists, boxed in behind sheeting, and closed up for the life of the building. It was never designed to come back out.
Threaded through the structure — access from below only.
Metres of flexible duct, buried and sealed for the life of the home.
Here’s why that matters
You can service the fan-coil. You can change a filter. You can even add a UV lamp at the unit. But the metres of flexible duct between that unit and every room grille are sealed away where hands, brushes and cameras can’t practically follow.
Does any of this sound familiar?
- That distinctive “air-con smell” when the system first kicks on
- A musty note in the house you can’t trace to any one room
- Air that feels stale and recirculated, never quite fresh
- Cooking and pet smells that linger far longer than they should
- Someone in the house whose hay fever or asthma seems worse indoors
There can be other causes, and it’s worth ruling out the obvious ones first. But if the smell arrives with the air conditioning and fades when it’s off, the ductwork is a very reasonable place to look.
Why the obvious fixes don’t solve it
Duct cleaning has real limits
Flexible duct can only be lightly cleaned — the polyester inner core is thin enough that manufacturers and NADCA both caution against aggressive brushing or air-whipping. On a buried run you often can’t get equipment to it at all. And replacement means opening up ceilings.
A UV lamp alone can’t reach it
A germicidal lamp only works in its direct line of sight. Any shadow, any bend, and the light simply doesn’t get there. It treats the air passing the unit — not the metres of shaded liner and every branch downstream.
THE SOLUTION
Treat the air that travels through it.
If a brush and a lamp can’t get down the run, the alternative is to treat the air itself — and let the system’s own airflow carry that treatment the length of the duct. That’s what the BioZone InDuct is designed to do.
A small unit, fitted inside the duct
The InDuct sits inside your ductwork. A specialist UV lamp reacts with the oxygen and water vapour already in your passing air to create photoplasma — a short-lived, highly reactive mix of hydroxyl radicals, oxygen singlets, ions and a minimal amount of ozone.
That reactive mix is then carried by your air conditioning’s own airflow to every surface downstream — around bends, along the liner, and out to each room grille.
Photoplasma occurs in nature. It’s often called the “detergent” of the Earth’s atmosphere for the way it breaks down pollutants.
How photoplasma is made
UV light meets the oxygen and water vapour already moving through your ducts. The reaction produces reactive oxygen species and free radicals that break down contaminants, converting them into harmless end-products.
Because those species travel with the airflow rather than sitting still at the lamp, the benefit isn’t limited to the moment air passes the unit.
What it works on, continuously
- Mould and spores — helping suppress regrowth on the duct liner and at every grille
- Cooking, pet and musty odours — oxidised at the source, not masked with fragrance
- Airborne bacteria, viruses and VOCs — in the circulating air, right through every branch
Odours and VOCs — broken down, not masked
Most things people reach for when a house smells stale don’t actually remove the smell. Plug-ins, sprays and scented filters add a fragrance on top of it. The underlying compound is still circulating.
Photoplasma works differently. The reactive species it creates oxidise odour molecules and volatile organic compounds directly, breaking them down as the air passes through the duct — so the smell is dealt with rather than covered up.
Everyday household odours
- Musty, damp, “old house” smells
- The stale note when the air-con first starts
- Cooking smells that hang around — fried food, curry, fish
- Pet and litter-tray odours
- Bathroom and laundry smells carried on the return air
- Cigarette smoke residue
VOCs and chemical gases
- Formaldehyde — new carpet, cabinetry, engineered timber
- Off-gassing from fresh paint and new furniture
- Cleaning-product and aerosol residues
- Benzene and related compounds
- Ammonia and hydrogen sulfide
What the testing shows
BioZone commissioned third-party accredited laboratories to test the technology against a range of air pollutants under controlled conditions. Reported reductions included total VOCs, formaldehyde, ammonia and hydrogen sulfide, alongside airborne and surface bacteria and mould.
Those are laboratory figures under controlled test conditions, and we’d rather say so plainly. In a real home the result depends on airflow, humidity, how big the space is and how strong the source is — so treat them as an indication of what the technology does, not a promise of a number you’ll hit in your own house. We’re happy to talk through what’s realistic for your system.
Being straight with you about what it is
This is not an ozone generator. It produces only a minimal, low-level amount of ozone as a by-product — a fraction of what a dedicated ozone machine makes — and runs continuously at low output within Safe Work Australia workplace exposure guidance.
It’s designed to control and suppress. It doesn’t sterilise a house, and it isn’t a substitute for physical remediation if you already have heavy visible growth. What it does is keep working on the air, every day, in the part of your home nobody can get to.
How the ozone level compares — Australian reference points
The InDuct range is sized around nominal ozone concentrations, and residential selection normally uses the 0.013 ppm (13 ppb) column. For context, here’s how that sits against the Australian reference levels:
| Reference | Level |
|---|---|
| InDuct typical residential design setting | 13 ppb |
| NEPM ambient air quality standard, Australia (8-hour average) | 65 ppb |
| Safe Work Australia workplace exposure standard for ozone | 100 ppb (0.1 ppm) |
Two things worth being clear about. Australia has no binding residential indoor ozone standard, so there is no perfect benchmark to point at — the figures above are an ambient outdoor standard and a workplace standard respectively, and neither was written specifically for a home. They’re offered as context, not as an approval. And Safe Work Australia is replacing its Workplace Exposure Standards with Workplace Exposure Limits from 1 December 2026; we’ll update this figure if the ozone value changes.
Fitting it is a straightforward job
The InDuct mounts into the ductwork itself — out of sight, out of the way, and without obstructing your airflow. A qualified installer cuts a single 70 mm hole, seals the unit in, and plugs it into a standard outlet.
There are six steps to it, and none of them involve pulling ductwork out or opening a ceiling.
On site, it looks like this
The unit sits flush against the duct wall. A single power lead runs to a standard outlet. Once the ceiling tile goes back, there’s nothing to see.
And then you can forget about it
One moving part (the fan) and one consumable (the lamp, changed annually). It runs continuously in the background, drawing less power than a household light globe. Most people don’t notice it’s there.
Three sizes. One for your home.
Which model you need comes down to the floor area your system conditions, your ceiling height, and how strong the problem is. Not sure? Tell us about your system and we’ll work it out for you.
APARTMENTS & SMALLER HOMES
InDuct ID-30
For apartments, townhouses and compact 2–3 bedroom homes running a single ducted system.
Covers up to ~115 m²
$1,391.50 inc GST
MOST POPULAR
TYPICAL FAMILY HOME
InDuct ID-40
Sized for the typical Australian 3–4 bedroom family home with a single ducted system. Our most popular home model.
Covers up to ~250 m²
$1,573.00 inc GST
LARGER & DUAL-SYSTEM HOMES
InDuct ID-60
For larger homes, homes running two systems, and high-ceiling open-plan builds with substantial airflow.
Covers up to ~850 m²
$3,267.00 inc GST
Can’t reach the ductwork?
Treat the air that travels through it.
Tell us about your ducted system — how many bedrooms, roughly what floor area, and what you’re noticing. We’ll recommend the right model, arrange a qualified installer, and have it running quietly in the background.
TALK TO US TODAY
07 3705 5995
info@australianuv.com.au
Australia-wide supply · Brisbane-based, family-run business
What to expect — and what not to
We’d rather set this out plainly before you buy than have the conversation afterwards. None of it is fine print.
It controls and suppresses — it doesn’t remediate
If there’s already established, visible mould growth in your ducts or elsewhere in the building, this unit will not remove it. Physical remediation comes first. The InDuct is what helps keep the problem from returning afterwards, and what keeps a clean system from getting there in the first place.
It’s not a substitute for cleaning, ventilation or fixing a leak
If a smell is coming from a damp subfloor, a leaking shower, a blocked condensate drain or a wet wall cavity, treating the supply air won’t solve it. Those need fixing at the source. Worth ruling them out before you spend money here.
Results build up — it isn’t a shock treatment
The unit runs continuously at a low, controlled output rather than blasting a space in one go. Most people notice a difference in odour over days to weeks rather than the same afternoon, and the effect depends on how much your system runs. A unit in a house where the air conditioning is on an hour a day will do less than one in a house where it runs constantly.
Results vary — genuinely
Floor area, ceiling height, airflow, humidity, how the ductwork is laid out, how many people and pets are in the house, and how strong the odour source is all change the outcome. The manufacturer’s laboratory figures were produced under controlled test conditions and shouldn’t be read as a number you’ll measure in your own home.
Sizing is based on what you tell us
We size from the floor area, ceiling height, system layout and problem description you give us. If the actual space turns out to be significantly larger, or the system is zoned differently than described, the model may be undersized for the result you were hoping for. If you’re unsure of your numbers, say so and we’ll work through it rather than guess.
The lamp is a consumable
Rated at roughly 9,000 hours, which works out to about a year of continuous running. Output falls away as the lamp ages, so a unit running on a three-year-old lamp is not doing what it did when it was fitted. Annual replacement isn’t optional maintenance — it’s how the thing keeps working.
Installation must be done by a qualified person
It cuts into your ductwork and connects to mains power via the supplied adapter. We can arrange an installer, or your own HVAC contractor can fit it. It isn’t a DIY job, and a poorly sealed opening will cost you airflow.
If any of that changes how you feel about it, we’d rather you told us now. Call us and describe the actual problem you’re trying to solve — sometimes the honest answer is that something else needs doing first.
Questions people ask us
Is the ozone safe with kids and pets in the house?
The InDuct isn’t an ozone generator. It produces only a minimal, low-level amount as a by-product of the photoplasma reaction — a fraction of what a dedicated ozone machine makes — and it’s designed to run continuously at low output within Safe Work Australia workplace exposure guidance for ozone. It’s built to run in occupied homes.
How much maintenance is involved?
One lamp change a year. The unit has a single moving part (the fan) and a single consumable (the lamp). Nothing else to service.
Will I hear it?
No. It sits inside the ductwork, out of sight, and runs quietly in the background. Most people forget it’s there.
Does it replace getting my ducts cleaned?
Not exactly — and we’d rather be straight with you. If your ducts already have heavy visible growth, physical remediation is the first step. The InDuct is for ongoing control after that: it keeps working on the air and the surfaces so the problem doesn’t simply come back. For most homes that have never had an issue flagged, it’s preventative — it keeps the duct from getting to that state.
Can it go into an existing system, or only a new build?
Both. It’s designed for new builds and as a retrofit into existing ducted systems. Fitting is quick and doesn’t obstruct your airflow.
How do I know which model I need?
Give us a call and tell us your rough floor area, how many bedrooms, your ceiling height, and what you’re noticing. We’ll size it for you — you don’t need to work any of it out yourself.
Important · please read. The BioZone InDuct provides ongoing air disinfection and odour control — it helps suppress and reduce the airborne odour and microbial load in the treated air. It does not sterilise your home and is not a substitute for normal cleaning and ventilation; results vary with the size of the home, airflow, humidity and how the system is used. The unit produces only minimal, low-level ozone as a by-product and is designed to operate within the Safe Work Australia workplace exposure guidance for ozone; it must be installed by a qualified person. This is general product information and not a guarantee of a specific outcome; final model selection follows a review of your system.