“Clean every X years” is the answer most operators want. It’s also the wrong way to think about a commercial HVAC system. The honest answer is that duct cleaning frequency is condition-based, not calendar-based - and in Perth, the conditions push harder than a single rule of thumb allows for.
Here’s how we set a defensible cleaning interval for the commercial systems we look after across the metro and the wider state.
The standard sets a regime, not a date
AS/NZS 3666.2 - Air-handling and water systems of buildings: Microbial control - Operation and maintenance - is the standard that governs this work. It doesn’t hand you a fixed “clean the ducts every two years” figure. What it requires is a maintenance regime: scheduled inspections, recorded condition assessments, and cleaning triggered when an inspection shows a system has drifted from a clean baseline.
That distinction matters. A building that books a clean every two years and never inspects in between is technically doing maintenance, but it has no idea what its system is doing for 23 of every 24 months. A building that inspects regularly and cleans on condition will usually spend less and carry less risk.
What pushes the interval in a Perth building
Two identical office blocks can need very different schedules. The variables that move the needle:
- Filtration quality - a system running coarse filters loads its ducts far faster than one with well-maintained fine filtration.
- Outdoor air and location - coastal sites carry salt aerosol; sites near construction, industry or major roads pull in more particulate.
- Occupancy and use - a 24/7 healthcare facility is a different animal to a nine-to-five office.
- Perth’s climate - hot dry summers move a lot of fine dust, and humidity events through the shoulder seasons give any organic material in a duct the moisture it needs to become a problem.
- History - any water ingress, nearby renovation, or a previous mould issue resets the clock.
Indicative intervals by building type
These are practical starting points, not a substitute for inspection. We’d confirm or adjust each one after looking at the system:
- Healthcare, aged care and laboratories - a full clean at least annually, with six-monthly inspections. The air-quality stakes are highest here.
- Hospitality and food service - annually for the HVAC side. Your kitchen exhaust runs to a separate, more frequent AS 1851 schedule.
- Offices, retail and commercial - every one to two years, leaning to annual if filtration is basic or occupancy is high.
- Mining accommodation and coastal industrial - six to twelve months, for the reasons above.
- After any incident - water damage, a mould finding, or heavy nearby renovation - clean now, then re-baseline.
Signs a system is already overdue
You don’t need a calendar to tell you some of these:
- Visible dust or debris around supply diffusers
- Musty or stale odours when the system kicks in
- Occupant complaints - headaches, congestion, “stuffy” rooms
- A recent water leak, flood or condensation event
- No documented clean in the last two years, or no records at all
Any one of those is worth an inspection. Two or more, and you’re likely carrying a burden the system has held for months.
Set a programme, not a panic
The cheapest duct cleaning we deliver is never the emergency one after a complaint or a failed audit. It’s the planned cycle - scheduled inspections, condition-based cleaning, and a documented record you can hand to a building owner, auditor or insurer without explanation. That’s the whole point of commercial duct cleaning done properly.
If you run commercial assets around Perth and you’re not sure where yours sit, talk to us. We’ll inspect, tell you honestly whether a clean is due, and set an interval that fits the building rather than a generic table.